The pulmonary neuroendocrine cell (PNEC) system consists of solitary cells and distinctive cell clusters termed neuroepithelial bodies (NEB) localized in the airway epithelium. PNEC/NEB express a variety of bioactive substances, including amine (serotonin, <em>5HT</em>) and neuropeptides. We have previously shown that NEB cells are O(2) sensors expressing nicotinamide adenine diphosphate oxidase complex and O(2) sensitive K(+) channel. Recently, we demonstrated expression of functional cystic fibrosis transmembrane conductance regulator (CFTR) and Cl(-) conductances in NEB cells of rabbit neonatal lung. Because PNEC/NEB are sparsely distributed and difficult to study in native lung, we investigated small-cell lung carcinoma (SCLC) and carcinoid tumor cell lines (tumor counterparts of normal PNEC/NEB) as models for PNEC/NEB. SCLC (H146, H345) and carcinoid (H727) cell lines express neuroendocrine cell markers, including chromogranin A, neural cell adhesion molecule (N-CAM), <em>5HT</em>, and tryptophan hydroxylase. We report that H146, H345, and H727 express CFTR messenger RNA (reverse transcription polymerase chain reaction) and protein (immunoblotting) and possess functional CFTR Cl(-) conductance, demonstrated by an iodide efflux assay inhibitable by transfection with antisense CFTR. Using an immunoassay to quantitate <em>5HT</em> secretion, we also show that downregulation of CFTR abolishes hypoxia-induced <em>5HT</em> release, and reduces secretory response to high potassium. Our findings suggest that CFTR may modulate neurosecretory activity of PNEC/NEB possessing O(2) sensor function. We propose that these tumor cell lines may be useful models for investigating the role of CFTR in PNEC/NEB functions in health and disease.

The modulatory actions of 5-hydroxy-tryptamine (<em>5HT</em> or serotonin) on a morphologically identifiable class of neurons dissociated from antennal lobes of Manduca sexta at stages 9-15 of the 18 stages of metamorphic adult development were examined in vitro with whole-cell patch-clamp recording techniques. Action potentials could be elicited from approximately 20% of the cells. These cells were used to examine effects of <em>5HT</em> (5 x 10(-6) to 5 x 10(-4) M) on cell excitability and action-potential waveform. <em>5HT</em> increased the number of spikes elicited by a constant depolarizing current pulse and reduced the latency of responses. <em>5HT</em> also led to broadening of action potentials in these neurons and increased cell input resistance. Modulation of potassium channels by <em>5HT</em> is likely to contribute to these responses. <em>5HT</em> causes reversible reduction of at least 3 distinct potassium currents, one of which is described for the first time in this study. Because effects of <em>5HT</em> on antennal-lobe neurons in culture mimic those observed in situ in the brain of the adult moth, in vitro analysis should contribute to elucidation of the cellular mechanisms that underlie the modulatory effects of <em>5HT</em> on central olfactory neurons in the moth.

This experiment examined the effect of destruction of the ascending 5-hydroxytryptaminergic (<em>5HT</em>ergic) pathways on performance in a free-operant timing schedule. Rats received either injections of 5,7-dihydroxytryptamine into the dorsal and median raphe nuclei or sham lesions. They were trained to press levers for a sucrose reinforcer. Training sessions consisted of 40, 50-s trials in which reinforcers were available on a variable-interval 25-s schedule; in the first 25 s of each trial, reinforcers were only available for responses on lever A, whereas in the last 25 s reinforcers were available only for responses on lever B. Data were collected from probe trials (four per session) in which no reinforcers were delivered, during the last ten of 50 training sessions. Both groups showed decreasing response rates on lever A and increasing response rates on lever B as a function of time from the onset of the trial. Response rate on lever B, expressed as a percentage of overall response rate, could be described by a two-parameter logistic function; neither the indifference point (i.e. the time corresponding to 50% responding on lever B) nor the slope of the function different between the two groups. However, the lesioned group showed a higher rate of switching between response alternatives than the sham-lesioned group. The levels of <em>5HT</em> and 5-hydroxyindoleacetic acid were reduced in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not significantly altered. The results confirm previous findings that behaviour in timing schedules is sensitive to destruction of the central <em>5HT</em>ergic pathways, and suggest that these pathways may contribute to the inhibitory regulation of switching between behavioural states.

A series of 3-(3',4'-dichlorophenyl)-1-indanamine monoamine reuptake blockers have been synthesized in an effort to develop a compound that could be used as a maintenance therapy to treat cocaine abuse. Since the effects of cocaine on dopamine (DA) and serotonin (<em>5HT</em>) transporters are important components of its pharmacological activity, the focus was on nonselective inhibitors of monoamine transport. To reduce or eliminate the abuse potential of a DA reuptake blocker, the compounds were designed to be slow-onset, long-duration prodrugs whose N-demethylated metabolites would have increased activity over the parent compound with the ideal being a parent compound that has little or no activity. To achieve this, pairs of compounds with different groups on the amine nitrogen and with and without an additional N-methyl group were synthesized. All of the synthesized compounds were screened for binding and reuptake at the cloned human DA, <em>5HT</em>, and norepinephrine (NE) transporters. As previously found, trans isomers are nonselective blockers of DA, <em>5HT</em>, and NE reuptake, cis isomers with small N-alkyl groups are selective blockers of <em>5HT</em> reuptake, and tertiary amines of the trans compounds are less potent than the corresponding N-demethylated secondary amines as blockers of DA reuptake. Larger N-alkyl groups in both the trans and cis series were found to reduce activity for the <em>5HT</em> and NE transporters with less effect at DA transporters. Selected trans compounds were also screened for locomotor activity in mice and generalization to a cocaine-like profile in rats. With intraperitoneal administration, all of the trans isomers showed a slow onset of at least 20 min and an extremely long duration of action in the locomotor assays. Several of the trans compounds also fully generalized to a cocaine-like pharmacological profile. An initial lead compound, the N,N-dimethyl analogue trans-1b, was resolved into chirally pure enantiomers. Surprisingly, both enantiomers were found to have significant affinity for the DA transporter and to cause locomotor activation. This is in contrast to the N-methyl compound in which only the (+)-enantiomer had significant activity. The absolute configuration of the more active enantiomer was determined by X-ray crystallography to be 3R,1S.

The E isomer of (123)I-2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(1-iodoprop-1-en-3-yl)nortropane (Altropane(R)) shows high affinity (IC(50) = 6.62 +/- 0.78 nmol) and selectivity (DA/5-HT = 25) for DAT sites in the striatum. Recently, dynamic SPECT studies in healthy volunteers and patients with Parkinson disease demonstrated that the kinetics of striatal accumulation followed a pattern that is characteristic of a reversible tracer with maximal accumulation within 30 min after injection. These findings suggested that radiolabeling Altropane with [(11)C] might provide an equivalent and complementary tracer for PET studies. [(127)I] Altropane was treated with HCl to hydrolyze the methyl ester bond and yield a precursor for [(11)C] labeling. Introduction of an [(11)C] methyl ester group was achieved by treatment with [(11)C] CH(3)I followed by HPLC purification. Five healthy rhesus monkeys were injected with approximately 10 mCi of [(127)I,(11)C] Altropane and dynamic PET images were acquired over 90 min. Arterial blood samples were collected in parallel with imaging and metabolite analysis was performed by HPLC. The PET and metabolite corrected arterial blood data were to calculate k(3)/k(4) by two methods: 1) nonlinear least-squares fitting, and 2) a linear graphical method for reversible ligands. The synthetic procedure yielded high specific activity tracer, >1,000 mCi/micro mole, with radiochemical purity >95%. Synthesis time was approximately 30 min. The PET images revealed excellent striatal definition, with clear separation of caudate nucleus and putamen and minimal accumulation in brain regions with high <em>5HT</em> transporter density. Metabolite analysis demonstrated that at 60 min after injection, approximately 80% of circulating tracer was intact [(127)I,(11)C] Altropane and the remainder was converted to polar metabolites. Values for k(3)/k(4) calculated by two analysis methods were remarkably similar: Method 1, 3.48 +/- 0.41; Method 2, 3.77 +/- 0.45 (mean +/- SEM, t = 2.31, df = 8, P = 0.64). These results establish that Altropane has the important characteristics of: 1) rapid and specific striatal binding; 2) high selectivity for DA vs. 5-HT transporter sites; 3) reversible binding kinetics; 4) potential for multiple injection studies; 5) high efficiency labeling with either [(11)C] or [(123)I]; 6) applicability for both PET and SPECT. These properties make Altropane an important DAT ligand for both research and clinical applications.

Fischer-344 rat pups were injected with either 10 mg/kg delta 9-tetrahydrocannabinol (THC) or vehicle on postnatal days 4,6 and 8. Pups were then allowed to mature. On day 129 of age rats were exposed to a stress paradigm which consisted of inescapable electric foot-shock administered at 1 mA for 15 sec daily for 8 days. Analgesia induced by foot-shock was measured by tail withdrawal from 55 degree C water. On the 9th day rats were exposed to the shock environment only. Fifteen minutes following measurement of tail withdrawal, animals were sacrificed. Plasma corticosterone and prolactin were measured. Levels of norepinephrine, dopamine and 5-hydroxytryptamine and metabolites were determined in frontal cortex, hippocampus and hypothalamus. Neonatal exposure to THC produced an increase in baseline tail withdrawal latency. No effect of THC exposure was seen on acute stress-induced analgesia. Rats exposed to THC required a greater number of conditioning trials to develop conditioned analgesia than animals treated neonatally with vehicle. The conditioned stress increased plasma corticosterone without affecting prolactin. Stress increased hypothalamic <em>5HT</em> and 5HIAA while decreasing <em>5HT</em> turnover in this area. Dopamine and DOPAC levels in the hypothalamus and frontal cortex were increased by stress; dopamine turnover in the frontal cortex was elevated by stress. Neonatal THC and stress elevated norepinephrine above control levels in the hypothalamus, while increasing <em>5HT</em> in the hippocampus and frontal cortex. The stress-induced increase in DOPAC in the frontal cortex was decreased by THC exposure. These data suggest that long-term neurochemical changes may occur with neonatal administration of THC.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution of monoamine (MA)-containing nerve cell bodies in the brain stem of the chicken (Gallus domesticus) was studied by means of paraformaldehyde and glyoxylic acid fluorescent histochemical methods. The MA neurons were further characterized morphologically and histochemically in material prepared for the demonstration of acetylcholinesterase (AChE). In the rostral midbrain of the chicken, two large collections of catecholamine (CA)-containing cells are found: one located in the ventromedial and the other in the dorsolateral (pedunculopontine nucleus) portions of the tegmentum. On the basis of their topographic location, CA content, and fiber connections, these ventromedial and dorsolateral cell groups can be tentatively associated with the CA-containing neuronal populations of the mammalian ventral tegmental area and pars compacta of the substantia nigra, respectively. In the caudal midbrain of the chicken, numerous CA-containing cells are intermingled with serotonin (<em>5HT</em>)-containing perikarya beneath as well as within the decussation of the superior cerebellar peduncles. At isthmus levels, abundant, closely-packed CA-containing cells are encountered along the lateral border of the central gray. These neurons, which display a very high AChE activity, appear to be equivalent to those of the mammalian locus coeruleus. A multitude of medium-sized <em>5HT</em>-containing neuronal somata occurs within the raphe region of the isthmus. Some of these somata closely surround the medial longitudinal fasciculus. This <em>5HT</em>-containing cell group also massively invades the lateral tegmentum, where it becomes closely intermingled with the CA-containing neurons of the locus coeruleus and subcoeruleus. All of these 5 HT-containing neurons display a moderate to high AChE activity. In the medulla the number of MA-containing neurons is much smaller than in the upper brain stem. Nevertheless, <em>5HT</em>-containing cells are present within the raphe region, particularly in the upper two-thirds of the medulla, and CA-containing perikarya can be found along the lateral border of the medulla and within the confines of the nucleus solitarius. The findings of the present study reveal that the MA-containing neuronal systems in the avian brain stem are organized according to a pattern that is much more complex than the one disclosed in reptiles or in other nonmammalian vertebrates. This complexity arises in large part from the fact that the <em>5HT</em>-containing systems undergo a prominent lateralization in birds, which leads to a close intermingling of <em>5HT</em>-containing and CA-containing neuronal elements at various levels of the neuraxis.

Serotonin (<em>5HT</em>) induces short-term and long-term synaptic facilitation (STF and LTF, respectively) at sensory neuron to motor neuron (SN-MN) synapses in Aplysia, and these forms of plasticity are thought to contribute to short-term and long-term memory for behavioral sensitization. Recent evidence in Aplysia has identified a third phase of synaptic facilitation-intermediate-term facilitation (ITF)-that is temporally and mechanistically distinct from STF and LTF. Here, we review the findings of recent studies that have examined this unique intermediate-term phase at molecular, cellular, and behavioral levels. The results indicate that, at tail SN-MN synapses, multiple forms of ITF can be distinguished; they are induced via distinct mechanisms and use parallel molecular pathways for their expression. Moreover, we have incorporated the temporal and molecular features of these different forms of ITF at tail SN-MN synapses into behavioral analyses, and found that they accurately predict distinct forms of intermediate-term memory for sensitization of the tail-elicited siphon withdrawal reflex. These findings indicate that different types of experiences engage distinct molecular pathways in the service of memory retention over the same time domain.

Long-term exposure to low levels of lead (Pb) has been shown to produce behavioral disturbances in humans and animal models. Additionally, these disturbances have been shown to be associated with alterations in neurotransmitter systems in certain brain regions. The study presented here was undertaken to examine the effects of low level exposure to Pb on two neurotransmitter systems in various brain regions during the postweaning period. Exposure of twenty-one day old male Long-Evans rats to 0, 25, 50, or 500 ppm Pb (as lead acetate in drinking water) for 90 days resulted in mean blood Pb levels of 4, 13, 15 and 49 micrograms/dl respectively. Similarly, this exposure protocol produced dose-dependent increases in Pb contents of various regions of brain. Frontal cortex (FC), nucleus accumbens (NA), striatum (ST), hypothalamus (HY), hippocampus (HIP) and brainstem (BS) regions were analyzed for dopamine (DA), serotonin (<em>5HT</em>) and their metabolites. Measurements of DA in brain regions indicated that while DA contents of NA and HY were significantly reduced by the subchronic Pb exposure, its levels in FC and HIP were not affected by the low level exposures (25 and 50 ppm) to Pb, and were actually increased by exposure to 500 ppm Pb. Dopamine metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) showed changes similar to DA. No significant changes in DA or its metabolites were observed in BS or ST in Pb-exposed animals. Serotonin content, on the other hand, showed consistent decreases in NA, FC, and BS in response to Pb with no changes in ST, HY, and HIP. Levels of the serotonin metabolite, 5-hydroxyindole acetic acid (5HIAA), were found to be decreased only in FC. These findings are of significance because the blood Pb values found at the two lower levels of Pb exposure (i.e., 25 and 50 ppm) were similar to those observed in children at risk for neurotoxicity (10-19 micrograms/dl). Additionally, these results suggest that the nucleus accumbens appears to be a preferentially susceptible area of the brain for Pb-induced neurotoxicity.

Dopamine (DA) concentrations in the rat striatum and/or nucleus accumbens were decreased by lesions in the nigra, ventral tegmentum, striatum and accumbens induced by 6-hydroxydopamine. These affected a range of DA- and 5-hydroxytryptamine-(<em>5HT</em>) dependent behaviours induced by 25 mg/kg of D-amphetamine as follows. Changes in DA-dependent behaviour (forward locomotion, head bobbing) occurred which were consistent with DA terminals in the accumbens and striatum being required for locomotor and stereotypical behaviour, respectively. A repetitive <em>5HT</em>-dependent behaviour (head weaving) was decreased by lesions which depleted striatal DA. A <em>5HT</em>-dependent behaviour with repetitive and locomotor elements (reciprocal forepaw treading) was only decreased by the nigral and tegmental lesions which depleted DA in both the striatum and the accumbens (and presumably also in other regions). These results suggest that <em>5HT</em>-dependent behaviours of stereotypical character also require DA. Conversely, two <em>5HT</em>-dependent behaviours, without obvious stereotypical or locomotor elements (body shakes, hind limb abduction), were not decreased by any of the lesions (and increased by some). Backward walking was markedly inhibited by lesions which decreased striatal DA. The above evidence for different relationships between each of the <em>5HT</em>-dependent behaviours studied and DA-containing systems implies that these behaviours are separately mediated. It may clarify previous disagreement on the role of DA in these behaviours.

The distribution and morphology of serotonin-like immunoreactive (<em>5HT</em>-IR) nerve cells, fibres and terminals in the rat ventromedial mesencephalic tegmentum (VMT) was studied using qualitative and quantitative immunohistochemical methods at light and electron microscopic levels. All five component nuclei were examined and the size, number and density of immunoreactive neurons and terminals determined. Thirty percent of all neurons in the caudal linear nucleus and 1% in the interfascicular nucleus were immunoreactive for serotonin. Different regions of the VMT had morphologically distinct <em>5HT</em>-IR fibres and quantitative differences between the VMT nuclei were seen in the density of <em>5HT</em>-IR terminals. In the lateral VMT, many thick, nonvaricose <em>5HT</em>-IR fibres were found in the parabrachial pigmented nucleus while many fine, varicose <em>5HT</em>-IR fibres were found in the paranigral nucleus. Fine, varicose <em>5HT</em>-IR fibres were also seen in the rostral and caudal linear nuclei. Many <em>5HT</em>-IR axon profiles formed synapses with small calibre dendrites. <em>5HT</em>-IR fibres in the interfascicular nucleus were thick with variable sized varicosities at irregular intervals. Few <em>5HT</em>-IR axon profiles formed synapses in this nucleus. A comparison between the number of <em>5HT</em>-IR terminals and the total number of axon terminals in the VMT (25) reveals that the majority of all terminals in the paranigral and rostral linear nuclei can be labelled with serotonin. The effect of serotonin on VMT cells is therefore likely to be mediated by different types of <em>5HT</em>-IR fibres which preferentially innervate particular VMT nuclei.

The etiology of late-onset Alzheimer's disease (AD) and idiopathic Parkinson's disease (PD) is not known. In both disorders there is an extensive degeneration of serotonergic neurons, with corresponding losses of the serotonin (<em>5HT</em>) transporter (<em>5HT</em>T), which is responsible for the reuptake of <em>5HT</em> from the synaptic cleft. An increasing body of evidence indicates that allelic variation of the <em>5HT</em>T gene promoter (<em>5HT</em>T gene-linked polymorphic region, <em>5HT</em>TLPR) determines high or low <em>5HT</em> uptake in normal human brain. Association studies show that the low-activity allele of the <em>5HT</em>TLPR is a risk factor for late-onset AD. In PD, the <em>5HT</em>TLPR influences the risk of developing depression, a common symptom in PD patients. A compromised serotonergic system thus plays an important role in the pathophysiology of both AD and PD.

Neurotransmitter transporters couple the transport of transmitter against its concentration gradient to the electrochemical potential of associated ions which are also transported. Recent studies of some neurotransmitter transporters show them to have properties of both traditional carriers and substrate-dependent ion channels, in that ion fluxes are in excess of that predicted from stoichiometric substrate fluxes. Whether these properties are comparable for all transporters, the extent to which these permeation states are independent, and whether the relationship between these two states can be regulated are not well understood. To address these questions, we expressed the Drosophila serotonin (<em>5HT</em>) transporter (dSERT) in Xenopus oocytes and measured both substrate-elicited ion flux and <em>5HT</em> flux at various temperatures and substrate concentrations. We find that the ion flux and <em>5HT</em> flux components of the transport process have a significant temperature dependence suggesting that ion flux and transmitter flux arise from a similar thermodynamically-coupled process involving large conformational changes (e.g., gating). These data are in contrast to those shown for glutamate transporters, suggesting a different permeation process for <em>5HT</em> transporters. The relationship between ion flux and <em>5HT</em> flux is differentially regulated by chloride and <em>5HT</em>, suggesting that these permeation states are distinct. The difference in half-maximal <em>5HT</em> concentration necessary to mediate ion flux and <em>5HT</em> flux occurs at submicromolar <em>5HT</em> concentrations suggesting that the relative participation of dSERT in ion flux and <em>5HT</em> flux will be determined by the synaptic <em>5HT</em> concentration.

We identified a new form of activity-dependent modulation of the afterhyperpolarization (AHP) in tactile (T) sensory neurons of the leech Hirudo medicinalis. Repetitive intracellular stimulation with 30 trains of depolarizing impulses at 15-s inter-stimulus interval (ISI) led to an increase of the AHP amplitude (~60% of the control). The enhancement of AHP lasted for>>/=15 min. The AHP increase was also elicited when a T neuron was activated by repetitive stimulation of its receptive field. The ISI was a critical parameter for the induction and maintenance of AHP enhancement. ISI duration had to fit within a time window with the upper limit of 20 s to make the training effective to induce an enhancement of the AHP amplitude. After recovery from potentiation, AHP amplitude could be enhanced once again by delivering another training session. The increase of AHP amplitude persisted in high Mg(2+) saline, suggesting an intrinsic cellular mechanism for its induction. Previous investigations reported that AHP of leech T neurons was mainly due to the activity of the Na(+)/K(+) ATPase and to a Ca(2+)-dependent K(+) current (I(K/Ca)). In addition, it has been demonstrated that serotonin (<em>5HT</em>) reduces AHP amplitude through the inhibition of the Na(+)/K(+) ATPase. By blocking the I(K/Ca) with pharmacological agents, such as cadmium and apamin, we still observed an increase of the AHP amplitude after repetitive stimulation, whereas <em>5HT</em> application completely inhibited the AHP increment. These data indicate that the Na(+)/K(+) ATPase is involved in the induction and maintenance of the AHP increase after repetitive stimulation. Moreover, the AHP increase was affected by the level of serotonin in the CNS. Finally, the increase of the AHP amplitude produced a lasting depression of the synaptic connection between two T neurons, suggesting that this activity-dependent phenomenon might be involved in short-term plasticity associated with learning processes.

A single injection of 5-hydroxytryptamine (<em>5HT</em>, 1 mg/kg, s.c.) in rats stimulated resting oxygen consumption (Vo2) by 21 percent; this was reduced (to 8 percent) by pretreatment with hexamethonium (5 mg/kg, s.c.). DL-fenfluramine injection (20 mg/kg, s.c.) stimulated metabolic rate (Vo2) by about 40 percent, but caused only 11 and 15 per cent increases in animals pretreated with hexamethonium or metergoline (5 mg/kg, s.c.), respectively. Interscapular brown adipose tissue (BAT) activity, assessed from mitochondrial GDP-binding, was increased by 96 per cent in intact tissue 1 h after fenfluramine injection; this response was completely prevented by surgical sympathectomy of interscapular BAT. Metergoline significantly inhibited (by 46 percent) the acute thermic response (postprandial rise in Vo2) to a 40-kJ meal in normal rats, and depressed resting Vo2 in protein-deficient rats by 18 percent, but did not affect resting Vo2 in control animals. BAT activity (mitochondrial GDP-binding) was elevated by 56 per cent in rats fed the low-protein diet, but this difference was almost completely abolished by prior treatment with metergoline. These data demonstrate a potent thermogenic effect of fenfluramine which apparently involves serotonergic pathways and activation of sympathetic outflow to BAT, and indicate that acute thermic responses to food and chronic thermogenic responses to low-protein diets may also involve serotonergic mechanisms.

The localization and relative number of serotonergic (<em>5HT</em>) cell bodies in the brainstem of the cat were studied through the use of a specific immunocytochemical technique. A surprisingly large number of <em>5HT</em> cells were found in regions in addition to the classical raphe nuclei (obscurus, pallidus, magnus, centralis superior, and dorsalis). Foremost among these were: the ventral medulla, just dorsal to the pyramidal tract and inferior olivary complex, and especially the area in and around the lateral reticular nucleus; the dorsal pons, surrounding the central reticular core, and in the central gray area; and a region in the mesencephalon, in and around the interpeduncular nucleus. The advantages and disadvantages of the existing schemas for subdividing and labeling groups of brain <em>5HT</em> neurons are discussed.

Antennal motor activity of the honeybee was used to test the effects of sucrose stimuli and of serotonin and octopamine microinjections into the brain. The antennal scanning behavior was analyzed in behavioral experiments. Activity of an antennal muscle, the "fast pedicellus flexor muscle" which dominates scanning behavior, was used as a physiological measure of modulatory effects. A single sucrose stimulus applied to both the antenna and the proboscis leads to significant increases of the frequency of antennal scanning compared to those of untreated controls and animals stimulated with water. A single sucrose stimulus applied only to the antenna or the proboscis has no significant behavioral effects. Injection of small volumes (approximately 500 pl) of serotonin (<em>5HT</em>) or octopamine (OA) at concentrations of 10(-5) M into the dorsal lobe, the sensory motor center of the antenna, leads to functionally antagonistic behavioral effects. While <em>5HT</em> injection significantly reduces the antennal scanning frequency, OA significantly enhances it. The degree of behavioral modulation is significantly correlated with the activity of the animals. In animals which display low scanning activity, OA injection has an enhancing effect, while <em>5HT</em> has no effect. In contrast, <em>5HT</em> injection, but not OA injection, produces a behavioral effect in animals with high scanning activity. Behavioral changes and changes of activity of the fast pedicellus flexor muscle are closely correlated. Significant, functionally antagonistic effects of <em>5HT</em> and OA on muscle activity were found after injections of the compounds into the dorsal lobe. <em>5HT</em> leads to a reduction of the muscle potential frequency starting immediately after injection and lasting at least 15 min. OA injection results in an increase of frequency, which has its maximum 5 min after injection. The experiments demonstrate that sucrose, the reward stimulus during associative learning in the bee, also modulates motor activity under nonassociative conditions. The similar effects of sucrose stimulation and OA injection are consistent with the hypothesis that OA mediates the effects of sucrose stimuli.

There has been evidence since the early eighties that glucocorticoids, apart from their well known chronic effects, may have acute, short-term effects. However, a lack of understanding of the molecular mechanisms of action has hampered appreciation of these observations. Mounting evidence over the years has continued to confirm the early observations on a fast corticosterone control of acute behavioral responses. We summarize experimental data obtained mainly in rats but also in other species which show: (1) that glucocorticoid production is sufficiently quick to affect ongoing behavior; (2) that there exist molecular mechanisms that could conceivably explain the fast neuronal effects of glucocorticoids (although these are still insufficiently understood); (3) that glucocorticoids are able to stimulate a wide variety of behaviors within minutes; and (4) that acute glucocorticoid production (at least in the case of aggressive behavior) is linked to the achievement of the behavioral goal (winning). The achievement of the behavioral goal reduces glucocorticoid production. It is argued that glucocorticoids are regulatory factors having a well-defined behavioral role. Both the acute (stimulatory) effects and the chronic (inhibitory) effects are adaptive in nature. The acute control of behavior by corticosterone is a rather unknown process that deserves further investigation. The pharmacologic importance of the acute glucocorticoid response is that it may readily affect the action of pharmacologic agents. An interaction between acute glucocorticoid increases and noradrenergic treatments has been shown in the case of offensive and defensive agonistic behavior. Non-behavioral data demonstrate that acute increases in glucocorticoids may interfere with other neurotransmitter systems (e.g., with the <em>5HT</em> system) as well. These observations show the importance of taking into account endocrine background and endocrine responsiveness in behavior pharmacological experiments.

During the first 24 h of post-embryonic development in Xenopus laevis, a rapid change in the neural activity underlying swimming occurs in which the duration of ventral root discharge on each cycle increases from a single compound impulse to discrete bursts of activity. Moreover, this change in motor output progresses rostrocaudally, suggesting that it could result from the influence of a descending neural pathway upon the spinal rhythm-generating circuitry during early post-embryonic development. To begin to examine whether serotonergic neurons of brainstem raphe nuclei might have a role in this swimming development, we have studied the effects of 5-hydroxytryptamine (<em>5HT</em>) on fictive swimming in embryonic and larval animals. As previously demonstrated for other vertebrate locomotor rhythms, we find that bath-applied <em>5HT</em> enhances the duration of motor activity on each cycle of larval fictive swimming. In addition, our results show that the sensitivity of the swimming rhythm to exogenous <em>5HT</em> follows a strict rostrocaudal gradient. In young embryos (stages 32-36) <em>5HT</em> does not affect the duration of ventral root impulses per cycle; by the time of hatching (stage 37/38), rostral but not caudal discharge is enhanced, and by stage 42 (24 h post-hatching) <em>5HT</em> can increase motor burst durations along most of the length of the animal. These reversible changes induced by bath-applied <em>5HT</em> closely resemble the normal rostrocaudal development of burst discharge during swimming in animals some 12 h older.(ABSTRACT TRUNCATED AT 250 WORDS)

BACKGROUND

The interoceptive and reinforcing effects of 3,4-methylenedioxymethamphetamine (MDMA) are similar to those of psychostimulants, but the role of dopamine in the behavioral effects of MDMA is not well documented, especially in primates.

OBJECTIVE

The aim of this study was to assess the role of dopamine in the behavioral effects of MDMA in two nonhuman primate species.

METHODS

The behavioral effects of MDMA, with and without serotonergic or dopaminergic pretreatments, were studied in squirrel monkeys trained to respond under a fixed-interval schedule of stimulus termination; effects on caudate dopamine levels were studied in a separate group of squirrel monkeys using in vivo microdialysis. Positron emission tomography neuroimaging with the dopamine transporter (DAT) ligand [18F]FECNT was used to determine DAT occupancy by MDMA in rhesus monkeys.

RESULTS

MDMA (0.5-1.5 mg/kg) did not induce behavioral stimulant effects, but the highest dose of MDMA suppressed responding. Pretreatment with fluoxetine (3.0 mg/kg) or the selective <em>5HT</em>(2A) antagonist M100907 (0.03-0.3 mg/kg) attenuated the rate suppressing effects of MDMA. In contrast, pretreatment with the selective dopamine transporter inhibitor RTI-177 (0.1 mg/kg) did not alter the rate suppressing effects of MDMA. Administration of MDMA at a dose that suppressed operant behavior had negligible effects on extracellular dopamine. The percent DAT occupancy of MDMA at a dose that suppressed operant behavior also was marginal and reflected low in vivo potency for DAT binding.

CONCLUSIONS

Collectively, these results indicate that behaviorally relevant doses of MDMA do not induce behavioral stimulant or dopamine transporter-mediated effects in nonhuman primates.

The laterodorsal tegmental nucleus (ntdl) contains a cluster of cells located just medial to the locus coeruleus in the pontine brainstem. The ntdl has been shown to project both rostrally to the forebrain and diencephalon and caudally to the spinal cord. In an effort to characterize this region neurochemically, the present study was conducted to identify a variety of neurochemicals localized within perikarya and fibers of the ntdl and surrounding nuclei. Rats were perfused with formalin, and brain sections were processed for fluorescence immunocytochemistry and acetylcholinesterase (AChE). Of the neurochemicals screened, atrial natriuretic factor (ANF), choline acetyltransferase (ChAT), cholecystokinin (CCK), calcitonin gene-related peptide (CGRP), dynorphin B (Dyn B), galanin, somatostatin, substance P, neurotensin (NT), neuropeptide Y (NPY), vasopressin, vasoactive intestinal polypeptide (VIP), serotonin (<em>5HT</em>), glutamic acid decarboxylase (GAD), and tyrosine hydroxylase (TH) were studied. AChE and ChAT staining revealed that the ntdl contains mostly cholinergic neurons. In addition, brightly reactive substance P and galanin and paler staining CRF, ANF, CGRP, NT, VIP, and Dyn B cell bodies were found within the ntdl. Varicose fibers in this nucleus also contained these peptides in addition to CCK, GAD, TH, <em>5HT</em>, and NPY. The dorsal tegmental nucleus, dorsal raphe nucleus, locus coeruleus, and the parabrachial region contained a dense and varied assortment of peptides with distinct positions and patterns. This multiplicity of neurochemicals within this area suggests a possible influence on a variety of functions modulated by the ntdl and other closely associated tegmental nuclei.

d-Amphetamine selectively promotes release of both dopamine (DA) and norepinephrine (NE) versus serotonin (<em>5HT</em>), and chronic d-amphetamine treatment decreases cocaine-taking behavior in rats, nonhuman primates, and humans. However, abuse liability limits the clinical utility of amphetamine maintenance for treating cocaine abuse. One strategy to improve safety and efficacy of monoamine releasers as candidate anticocaine medications has been to develop dual DA/<em>5HT</em> releasers like 1-napthyl-2-aminopropane (PAL-287), but the pharmacology of this class of compounds has not been extensively examined. In particular, PAL-287 has similar potencies to release DA, <em>5HT</em>, and NE, and the role of manipulating NE release potency on abuse-related or anticocaine effects of dual DA/<em>5HT</em> releasers is not known. To address this issue, the present study compared effects of four novel DA/<em>5HT</em> releasers that varied >800-fold in their selectivities to release DA/<em>5HT</em> versus NE: [1-(5-chloro-1H-indol-3-yl)propan-2-amine (PAL-542), 1-(5-fluoro-1H-indol-3-yl)propan-2-amine (PAL-544), 1-(1H-indol-5-yl)propan-2-amine (PAL-571), and (R)-1-(1H-indol-1-yl)propain-2-amine (PAL-569). Abuse-related effects of all four compounds were evaluated in assays of intracranial self-stimulation (ICSS) in rats and cocaine discrimination in rats and monkeys, and none of the compounds reliably facilitated ICSS or substituted for cocaine. Anticocaine effects of the compound with highest selectivity to release DA/<em>5HT</em> versus NE (PAL-542) were tested in an assay of cocaine versus food choice in rhesus monkeys, and PAL-542 failed to reduce cocaine choice. These results suggests that potency to release NE has minimal influence on abuse liability of dual DA/<em>5HT</em> releasers, and reducing relative potency to release NE versus DA/<em>5HT</em> does not improve anticocaine efficacy.

In a previous study we found that a tryptophan-deficient amino acid mixture, designed to lower tissue tryptophan and thus brain 5-hydroxytryptamine (<em>5HT</em>) levels, caused a rapid (5 h) lowering of mood in normal males. Because of the importance of this evidence indicating a direct causal connection between low <em>5HT</em> and low mood, we have now investigated other possible explanations for the mood lowering effect. Research strongly supports the involvement of environmental setting and cognition in the production and experience of emotions. Therefore we investigated how these factors might influence the mood-lowering effects of tryptophan depletion. In an instructional manipulation subjects were either supplied or not supplied with information designed to account for any possible peripheral sensations that might be related to depressive affect. In an environmental manipulation subjects were exposed either to a supportive and comfortable atmosphere (positive environment), or an unrewarding and unstimulating environment (negative environment). In the control group, which received a balanced amino acid mixture, the positive and negative environments had the expected effects on the scores of the Multiple Affect Adjective Checklist, thus indicating the effectiveness of these procedures. In the tryptophan depletion group neither the instructional nor the environmental manipulation had any influence on the mood lowering effect. It may be that tryptophan depletion lowers mood in normal males because low <em>5HT</em> influences mood directly rather than via cognitive processes. Our data strongly support the idea that <em>5HT</em> exerts an effect on mood and that low <em>5HT</em> may, in some patients, be an important factor contributing to the etiology of clinical depression.

Previous studies have demonstrated an inhibition of agonist-induced inositol phospholipid breakdown and intracellular Ca2+ ([Ca2+]i) mobilization by phorbol esters in platelets. In this study, we have examined the effect of phorbol 12-myristate 13-acetate (PMA) on agonist-induced granule secretion and correlated it with agonist-induced [Ca2+]i mobilization, arachidonate and thromboxane (Tx) release in human platelets. With increasing times of incubation with PMA (10 s-5 min), the rise in [Ca2+]i induced by thrombin and the TxA2 mimetic, U46619, was increasingly inhibited (90-100% with 5 min incubation) and, correlating with this, thrombin-induced [3H]arachidonate, TxB2 and beta-thromboglobulin (beta TG) release were also inhibited. In addition, the conversion of exogenously added arachidonate to TxB2 was inhibited (50-80%) by a 10 s-5 min pretreatment with PMA. However, secretion of 5-hydroxy[14C]tryptamine (<em>5HT</em>) induced by thrombin or U46619 was not inhibited by 10 s-2 min incubations with PMA and, on the contrary, with low agonist concentrations, was potentiated by PMA in the absence of a significant rise in [Ca2+]i or endogenous Tx formation, to levels significantly greater than or equal to the sum of that obtained when agonist and PMA were added separately. With longer times of incubation with PMA (5 min), these synergistic effects became less pronounced as inhibitory effects of PMA on agonist-induced [14C]<em>5HT</em> secretion became apparent. The results indicate that, while PMA may cause an inhibition of agonist-induced [Ca2+]i mobilization resulting in an inhibition of agonist-induced arachidonate, TxB2 and beta TG release, its effects on agonist-induced <em>5HT</em> secretion may be complicated by [Ca2+]i-independent synergistic effects of agonist and PMA.