Using the rat vibrissa system, we provide evidence for a novel mechanism for the generation of movement. Like other central pattern generators (CPGs) that underlie many movements, the rhythm generator for whisking can operate without cortical inputs or sensory feedback. However, unlike conventional mammalian CPGs, vibrissa motoneurons (vMNs) actively participate in the rhythmogenesis by converting tonic serotonergic inputs into the patterned motor output responsible for movement of the vibrissae. We find that, in vitro, a serotonin receptor agonist, alpha-Me-<em>5HT</em>, facilitates a persistent inward current (PIC) and evokes rhythmic firing in vMNs. Within each motoneuron, increasing the concentration of alpha-Me-<em>5HT</em> significantly increases the both the magnitude of the PIC and the motoneuron's firing rate. Riluzole, which selectively suppresses the Na(+) component of PICs at low concentrations, causes a reduction in both of these phenomena. The magnitude of this reduction is directly correlated with the concentration of riluzole. The joint effects of riluzole on PIC magnitude and firing rate in vMNs suggest that the two are causally related. In vivo we find that the tonic activity of putative serotonergic premotoneurons is positively correlated with the frequency of whisking evoked by cortical stimulation. Taken together, these results support the hypothesized novel mammalian mechanism for movement generation in the vibrissa motor system where vMNs actively participate in the rhythmogenesis in response to tonic drive from serotonergic premotoneurons.

Corticotropin-releasing factor (CRF), the key neuropeptide in the stress cascade, has major inhibitory actions on testicular function in addition to its known antireproductive effects at the central level (inhibition of sexual behavior and LH secretion). CRF is secreted by the Leydig cells of the testis and acts through high-affinity receptors at the Leydig cell membrane as a potent negative regulator of LH action, inhibiting gonadotropin-induced cAMP generation and androgen production. CRF is also a primary stimulus of beta-endorphin secretion by the Leydig cells, which in turn exerts paracrine inhibition of FSH action in the tubular compartment of the testis through high-affinity receptors in the Sertoli cells. CRF action in the Leydig cells involves a pertussis toxin-insensitive guanyl nucleotide regulatory unit. In contrast to CRF receptors in the brain, pituitary, and other peripheral tissues, those in the Leydig cell are not coupled to Gs. The inhibitory action of CRF in the Leydig cell is exerted through protein kinase C, at the level of the catalytic subunit of adenylate cyclase. The secretion of CRF by the Leydig cell is stimulated by LH, acting via release of serotonin (<em>5HT</em>) and autocrine activation of <em>5HT</em>2 receptors. Serotonin acts on <em>5HT</em>2 receptors in the Leydig cell to stimulate CRF secretion via a pertussis toxin insensitive G-protein and presumably through activation of phosphoinositide hydrolysis. The diversity of the biochemical responses to CRF and <em>5HT</em>2 receptor activation (i.e., inhibition of adenylate cyclase at the cytoplasmic aspect of the cell membrane vs. stimulation of CRF release from secretion granules) may reflect the stimulation of different protein kinase C isoenzymes. The LH->><em>5HT</em>->>CRF inhibitory loop serves to continuously buffer the stimulation of androgen production by gonadotropin. <em>5HT</em>, the immediate stimulus of testicular CRF secretion, is released during stress and is locally increased in the testis in pathological conditions associated with impaired testicular function (i.e., orchitis, varicocele). Also, propranolol, the beta-adrenergic antagonist frequently used in the control of blood pressure in patients with hypertension and often associated with impotence, acts via a serotonergic mechanism to stimulate CRF secretion and causes marked inhibition of LH-induced cAMP production and steroidogenesis in cultured Leydig cells. These basic studies of <em>5HT</em> and CRF are relevant to the pathogenesis of testicular dysfunction and for the development of antagonist therapies to block CRF production and its local antireproductive effects.

Serotonin (<em>5HT</em>) binding sites in autonomic portions of the dorsomedial medulla oblongata of the rat were localized using autoradiographic techniques with radioactive ligands that express high affinity for the <em>5HT</em>1 (3H-<em>5HT</em>), <em>5HT</em>1A (3H-8OH-DPAT), or <em>5HT</em>1B (125I-CYP with isoproterenol) receptor subtypes. <em>5HT</em>1A sites were densely distributed in the nucleus tractus solitarius (NTS), with the highest densities localized to the interstitial subnucleus and the central subnucleus. <em>5HT</em>1B sites were also found in the NTS, with the highest densities localized to the substantia gelatinosa subnucleus. The dorsal motor nucleus of the vagus nerve and nucleus ambiguus exhibited low densities of <em>5HT</em>1B sites. However, the nucleus intercalatus, a cerebellar relay nucleus that also contains dendrites of vagal parasympathetic preganglionic neurons and receives autonomic forebrain afferent input, showed very dense <em>5HT</em>1B sites. The promontorium, paratrigeminal islands, and the dorsomedial portion of the trigeminal nucleus (DM5), which are areas of viscerosomatic integration, exhibited high densities of both <em>5HT</em>1A and <em>5HT</em>1B sites. The area postrema contained low levels of both <em>5HT</em>1A and <em>5HT</em>1B sites. Visceral deafferentation via cervical vagotomy or nodose ganglionectomy caused a significant decrease in <em>5HT</em>1A sites in the interstitial subnucleus of the NTS ipsilateral to the lesion. No changes were seen in <em>5HT</em>1B sites. These studies suggest that <em>5HT</em>1A and <em>5HT</em>1B sites are involved in the processing of visceral sensory information in the NTS and associated areas. Based upon viscerotopic organization of the NTS, <em>5HT</em>1A sites appear preferentially distributed in portions of the NTS that are associated with the coordination of swallowing, respiration, and cardiovascular function, while <em>5HT</em>1B sites appear preferentially distributed in areas of the NTS associated with gastrointestinal, hepatic, pancreatic, and cardiovascular function. However, since these association were not absolute and there was a great deal of overlap between the two sites, speculation regarding their specific functions in autonomic control must await pharmacological examination.

The serotonin (<em>5HT</em>) reuptake transporter (SERT) plays a key role in <em>5HT</em> homeostasis by recycling <em>5HT</em> into the presynaptic neurons. Recently, polymorphisms in the length of the promoter region of the gene that encodes SERT have been linked to functional differences in reactivity to psychosocial stress, as the short (s) promoter length allele shows reduced transcriptionally activity in vitro and is associated with reduced <em>5HT</em> activity and increased vulnerability to affective disorders. Given <em>5HT</em>'s important role in appetite regulation, polymorphisms in the SERT gene could also affect metabolic parameters. In addition, since reduced <em>5HT</em> activity may also predispose females to reproductive deficits, polymorphisms in the SERT gene may help explain individual differences in ovulatory function. The present study, using a rhesus monkey model, tested the hypothesis that the presence of the s-variant allele would be associated with altered metabolic regulation and impaired ovulatory cycles compared with the l/l genotype. Females homozygous for the long allele in the SERT gene (l/l, n = 19) were compared to those with the s-variant allele (l/s or s/s, n = 20). All females had similar social histories. Body weights (P = 0.026) but not heights (P = 0.618) were significantly lower in s-variant compared to l/l females. In addition, both BMI (P = 0.032) and sagittal abdominal diameters (SAD) (P = 0.031), as indices of adiposity, were significantly lower in s-variant females. Consistent with these differences, fasting and non-fasting levels of leptin were significantly lower in s-variant females (P = 0.002). While there were no genotype differences in non-fasting levels of insulin, s-variant females had significantly lower concentrations of insulin during a fast than did l/l females (P = 0.052). Neither glucose, T 3, T 4, nor ghrelin varied significantly between groups during either the fasted or non-fasted condition (P>> 0.05). Analysis of a subset of females indicated that significantly fewer s-variant females (62.5%) exhibited ovulatory cycles than l/l females (100%, P < 0.05). However, there were no differences in serum estradiol or progesterone in l/l females and those s-variant females that did ovulate (P>> 0.05). In addition, females with the s-variant genotype also had reduced <em>5HT</em> activity (P = 0.030), assessed from the acute increase in serum prolactin following the administration of the <em>5HT</em> reuptake inhibitor, citalopram. Finally, s-variant females were significantly less responsive to glucocorticoid negative feedback (P = 0.030) yet more responsive to corticotropin releasing hormone (CRH, P = 0.016) in terms of plasma cortisol than were l/l females. These data indicate that adult female rhesus monkeys with the s-variant polymorphism in the SERT gene exhibit metabolic and reproductive alterations in conjunction with reduced serotonergic responsivity and increased LHPA activity and suggest the possibility that this genotype may predispose females exposed to psychosocial stressors to further metabolic and reproductive deficits.

Low doses of BHT 920, LY 171555 and (+)3PPP, three dopamine agonists selective for D-2 receptors, induced yawning in rats. This effect was reduced by the selective D-1 antagonist SCH 23390 but the antagonism did not exceed a 50% reduction from the control values. In contrast, the selective D-2 antagonist (-)sulpiride completely abolished agonist-induced yawning. A 6 h reserpine pretreatment (5 mg/kg i.p.), which depletes brain dopamine (DA) by about 95%, reduced agonist-induced yawning by an extent similar to SCH 23390; in the reserpinized rats, SCH 23390 completely lost the property of blocking agonist-induced yawning while (-)sulpiride retained it. Two <em>5HT</em> receptor antagonist, ketanserin and metergoline failed to influence agonist-induced yawning. The reportedly selective D-1 agonist, SKF 38393, failed to induce yawning in normal rats as well as in rats pretreated with reserpine 6 or 16 h earlier. If one excludes that SCH 23390 and the D-2 agonists interact with the same DA-receptors, the data are consistent with the possibility that stimulation of D-1 receptors by endogenous DA plays a permissive-facilitatory role for the behavioural expression of D-2 receptor activation.

Serotonin released from platelets may initiate coronary vasospasm in patients with variant angina. If this hypothesis is correct, serotonin antagonists without constrictor activity may be useful in this form of angina. We have investigated drugs classified as serotonin antagonists on dog circumflex coronary artery ring segments in vitro. Ergotamine, dihydroergotamine, bromocriptine, lisuride, ergometrine, ketanserin, trazodone, cyproheptadine and pizotifen caused non-competitive antagonism of serotonin concentration-response curves. In addition, ketanserin, trazodone, bromocriptine and pizotifen inhibited noradrenaline responses in concentrations similar to those required for serotonin antagonism. All drugs with the exception of ketanserin, cyproheptadine and pizotifen showed some degree of intrinsic constrictor activity. Methysergide antagonized responses to serotonin competitively but also constricted the coronary artery. The lack of a silent competitive serotonin antagonist precludes a definite characterization of coronary serotonin receptors at this time. However, the profile of activity observed for the antagonist drugs in the coronary artery differs from that seen in other vascular tissues. Of the drugs tested, ketanserin may be the most useful in variant angina since it is a potent <em>5HT</em> antagonist, lacks agonist activity and has alpha-adrenoceptor blocking activity.

Ondansetron (GR38032F), a serotonin <em>5HT</em>3 antagonist, is active in numerous behavioral paradigms and neurochemical systems. Since <em>5HT</em>3 antagonists have been suggested as therapeutic agents for the treatment of drug abuse, the action of ondansetron on cocaine drug discrimination and self-administration paradigms in rats was investigated. Doses of ondansetron (0.001 - 1.0 mg/kg) had no effect on the discriminative stimulus properties of 10 mg/kg cocaine. In contrast SCH23390, a dopamine D1 antagonist known to block cocaine discrimination, acted as previously reported. Ondansetron did not augment the effects of SCH23390, but at higher doses, combinations of ondansetron and SCH23390 produced disruption of lever pressing in the presence of cocaine. Ondansetron (0.001-1.0 mg/kg) had no effect on the self-administration of various doses of cocaine, nor did it have any effect on reacquisition of cocaine self-administration in animals with a history of active administration followed by a period of abstinence. As before, SCH23390, known to block cocaine self-administration, acted as previously reported. Although other <em>5HT</em> antagonists may prove to be efficacious in cocaine abuse, ondansetron appears unlikely to alter the subjective or rewarding stimulus properties of cocaine.

JC virus (JCV) is the causative agent of progressive multifocal leukoenchaphalopathy (PML). The disease develops when JCV gains access to the central nervous system, infects and destroys oligodendrocytes. The disease is rapidly progressing, typically fatal and no effective therapies exist to treat or prevent PML. The recent occurrence of PML in multiple sclerosis patients being treated with Avonex (IFNbeta1-a) and Tysabri (Natalizumab) and the recent reports linking JCV infection to the <em>5HT</em>(2a) serotonin receptor led us to evaluate the effects of IFNbeta1-a and a panel of <em>5HT</em>(2a) receptor antagonists for their ability to modulate virus infection. IFNbeta1-a was found to be a potent inhibitor of both virus infection and viral early and late gene expression. In addition, several <em>5HT</em>(2a) receptor antagonists inhibited initial infection of cells by JCV but were less effective at reducing viral loads in an already established infection.

Fetal coexposure to nicotine and dexamethasone is common: maternal smoking increases the incidence of preterm delivery and glucocorticoids are the consensus treatment for prematurity. We gave pregnant rats 3mg/kg/day of nicotine throughout gestation, a regimen that reproduces smokers' plasma levels, and then on gestational days 17, 18 and 19, we administered 0.2mg/kg of dexamethasone. We evaluated developmental indices for serotonin (<em>5HT</em>) and dopamine synaptic function throughout adolescence, young adulthood and later adulthood, assessing the brain regions possessing major <em>5HT</em> and dopamine projections and cell bodies. Males displayed persistent upregulation of <em>5HT</em>(1A) and <em>5HT</em>(2) receptors and the <em>5HT</em> transporter, with a distinct hierarchy of effects: nicotine<dexamethasone<combined treatment. Females showed downregulation of the <em>5HT</em>(1A) receptor with the same rank order; both sexes displayed presynaptic hyperactivity of <em>5HT</em> and dopamine pathways as evidenced by increased neurotransmitter turnover. Superimposed on these overall effects, there were significant differences in temporal and regional relationships among the different treatments, often involving effects that emerged later in life, after a period of apparent normality. This indicates that nicotine and dexamethasone do not simply produce an initial neuronal injury that persists throughout the lifespan but rather, they alter the developmental trajectory of synaptic function. The fact that the combined treatment produced greater effects for many parameters points to potentially worse neurobehavioral outcomes after pharmacotherapy of preterm labor in the offspring of smokers.

Rats tested for 1 h in the Behavioral Pattern Monitor (BPM) after injection of the mixed serotonergic agonist d-lysergic acid diethylamide (LSD) exhibit a behavioral profile similar to that produced by various hallucinogenic <em>5HT</em>-2 agonists. The characteristic effects of the hallucinogens include suppression of locomotor and exploratory behavior and a preferential decrease in entries into the center of the BPM during the initial half of the test session. After LSD, the initial suppression of responding is followed by a subsequent increase in locomotor activity that is not observed with other serotonergic agonists. In the present studies, the <em>5HT</em>-1 and beta-adrenergic antagonist d,l-propranolol and the <em>5HT</em>-2 antagonist ritanserin were administered individually or in combination prior to the acute administration of LSD to test for the involvement of these receptor subtypes in the mediation of the effects of LSD in the BPM paradigm. Propranolol (20 mg/kg) abolished the initial suppression of activity induced by 60 micrograms/kg LSD without affecting the subsequent increase in locomotion. Conversely, 2.0 mg/kg ritanserin failed to block the initial suppressive effects of 60 or 120 micrograms/kg LSD, but attenuated the LSD-induced increases in activity during the second half of the session. The combination of propranolol and ritanserin prevented both these effects of LSD. By contrast, the more selective <em>5HT</em>-2 agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) (0.27 mg/kg) produced an initial suppression of activity in the BPM that was blocked by 2.0 mg/kg ritanserin and was not followed by a subsequent increase in activity. (ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic-androgenic steroids (AAS) are partly misused by males in order to become brave and intoxicated and these agents are highly associated with psychosis, disinhibition, aggression and acts of violence. Since such behavioral states have been related to an imbalanced serotonergic system and the involvement of the serotonergic <em>5HT</em>(1B) and the <em>5HT</em>(2) receptors, it was important to discern the impact of AAS on these receptors. The objective of our study was to investigate the effects of 2 weeks of treatment with the AAS nandrolone decanoate at three different doses (1, 5, 15 mg/kg/day) on the total specific binding of the radioligands [(125)I]-(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (<em>5HT</em>(2) receptors) by autoradiography. All doses caused a significant down-regulation of the <em>5HT</em>(1B) receptor density in the hippocampal CA(1) and in the medial globus pallidus and a significant up-regulation of the <em>5HT</em>(2) receptor density in the nucleus accumbens shell. Alterations in receptor density were also observed in the lateral globus pallidus, ventromedial hypothalamus, the amygdala and in the intermediate layers of various cortex regions. In conclusion, serotonergic <em>5HT</em>(1B) or <em>5HT</em>(2) receptors are likely to play important roles in mediating observed emotional states and behavioral changes among AAS abusers.

There is a recognised association between pernicious anaemia and the development of gastric carcinoma, endocrine cell hyperplasia, and carcinoid tumour. Multiple endoscopic biopsies from the body mucosa of seven patients with pernicious anaemia showed small intestinal metaplasia with varying degrees of inflammation, fibrosis, and expansion of the lamina propria. Using conventional silver and lead stains, endocrine cells were inconspicuous. Staining for the general neural and neuroendocrine markers NSE and PGP 9.5 revealed a proliferation of endocrine cells in the epithelium and isolated clumps of endocrine cells in the lamina propria. The clumps were composed of two cell types, either small or large. Some of these endocrine cells showed gastrin, <em>5HT</em>, VIP and substance P immunoreactivity of varying intensity. Ultrastructurally nine morphologically distinct types of granules were found some of which correlated with the immunohistochemistry. Some separate islands were composed solely of endocrine cells while others had a definite neural component, suggesting that the former arise from 'budding off' of enteroendocrine cells and the latter originate from the neuroendocrine cells of the lamina propria plexus. Thus there may be a dual origin of carcinoid tumours. Carcinoid tumours associated with pernicious anaemia tend to be multifocal and are infrequent. Less than 50 such cases have hitherto been reported. Our findings of endocrine cells proliferations in seven cases of pernicious anaemia indicate that this may be an adaptive change that occurs frequently and provides the basis on which carcinoids, less frequently, develop.

1. Two pairs of neurons in the pyloric network of the spiny lobster, Panulirus interruptus, communicate through mixed graded chemical and rectifying electrical synapses. The anterior burster (AB) chemically inhibits and is electrically coupled to the ventricular dilator (VD); the lateral pyloric (LP) and pyloric (PY) neurons show reciprocal chemical inhibition and electrical coupling. We examined the effects of dopamine (DA), serotonin (<em>5HT</em>) and octopamine (Oct) on these mixed synapses to determine the plasticity possible with opposing modes of synaptic interaction. 2. Dopamine increased net inhibition at all three pyloric mixed synapses by both reducing electrical coupling and increasing chemical inhibition. This reversed the sign of the net synaptic interaction when electrotonic coupling dominated some mixed synapses, and activated silent chemical components of other mixed synapses. 3. Serotonin weakly enhanced LP->>PY net inhibition, by reducing electrical coupling without altering chemical inhibition. Serotonin reduced AB->>VD electrical coupling, but variability in its effect on the chemical component made the net effect non-significant. 4. Octopamine enhanced LP->>PY and PY->>LP net inhibition by enhancing the chemical inhibitory component without altering electrical coupling. 5. Differential modulation of chemical and electrical components of mixed synapses markedly changes the net synaptic interactions. This contributes to the flexible outputs that modulators evoke from anatomically defined neural networks.

The ultrastructure, cytochemistry, biochemistry, and functions of platelets from two patients with the familial gray platelet syndrome are described. Ultrastructural studies showed a lack of alpha-granules in the megakaryocytes in the vicinity of a marrow myelofibrosis and/or in platelets. A normal number of mitochondria and a slight increase of dense bodies was confirmed by labeling the whole patient with mepacrine. Platelet peroxidase (in the dense tubular system) and catalase-positive granules (revealed by the cytochemistry) were present. Platelets from both patients had severe deficiency of beta TG either after tritonization (less than 4% of normal) or thrombin treatment (less than 15% of normal), and the plasma beta TG levels were slightly increased. Functional studies of these platelets showed an uptake of [14C]<em>5HT</em> inhibited by reserpine similar to that in the control platelets. Thromboxane formation was within normal limits in the presence of arachidonic acid, ADP, collagen, or ionophore A23187, indicating that (1) the cyclooxygenase/thromboxane synthetase systems were not altered and (2) the phospholipase activities were not impaired. Although the platelet adhesion to prepolymerized fibrillar type III collagen and the ADP-, arachidonic acid-, and ionophore A23187-mediated aggregations were apparently normal, in every case the release of [14C]<em>5HT</em> was either at the low side of the normal range or decreased. This abnormality was increased when collagen or thrombin was added to either PRP or washed platelets from both patients, where at the same time, the aggregation and the release were markedly reduced. The results suggest that alpha-granules or their content has an influence on not only the platelet aggregation but also the dense bodies involved in the [14C]<em>5HT</em> release reaction.

To investigate whether depression is a consequence of disturbed function in <em>5HT</em> systems, neuroendocrine responses to infusions of the <em>5HT</em> precursor L-tryptophan (LTP) were studied in patients and controls. After an overnight fast and 60 min bed rest, a solution of LTP (10 g/l) was infused intravenously to a dose of 100 mg/kg over 30 min. Circulating growth hormone (GH), prolactin (PRL), cortisol and tryptophan concentrations were followed from 60 min pre-infusion to 60 min post-infusion. GH responses were attenuated in 23 major depressives (DSM-III) compared with 22 controls and were almost absent in endogenous depressives (New-castle criteria). PRL responses were normal in depressives who had lost more than 3 kg body weight but attenuated in those who had not. GH and PRL responses did not correlate with each other. Reduced basal tryptophan concentrations and more rapid tryptophan clearance were observed in the depressives, but there were no correlations with GH or PRL responses. However, basal cortisol concentrations, which were raised in depressives with chronic psychosocial difficulties, were strongly and inversely predictive of PRL responses in depressives and controls. Blunted GH and PRL responses to LTP appear to be distinct abnormalities in depression which may relate to two processes; (1), an endogenous mechanism indicated by reduced GH responses, and (2), an impairment in <em>5HT</em> systems, indicated by blunted PRL responses and perhaps caused by raised circulating cortisol or reduced tryptophan concentrations.

The activity of serotonergic (<em>5HT</em>) neurons in the dorsal raphe nucleus was inhibited by the i.v. administration of certain antipsychotic drugs (methiothepin, clozapine and thioridazine). However, other antipsychotic agents (chlorpromazine, haloperidol and pimozide) did not inhibit raphe cell firing. The inhibitory potency of these drugs on raphe activity correlates with reported central noradrenergic blocking efficacy. An alpha-adrenergic blocking agent, piperoxane, but not the beta-blocking agents, propranolol and MJ 1999, inhibited raphe activity when administered systemically. All of these drugs appear to act indirectly since they (and NE) have relatively weak or variable effects when applied microiontophoretically to raphe neurons. The depressant effects of certain antipsychotic drugs and piperoxane on <em>5HT</em> neurons appears to be mediated by a cnetral adrenergic system since (1) the depression could be reversed by the catecholamine releasing agents 1- and d-amphetamine; (2) the depression could be abolished by destruction of adrenergic pathways in the CNS by chemical, mechanical, or electrothermic lesions. While a precise localization has not yet been obtained, the data suggest that these drug effects may be mediated by an adrenergic pathway ascending from the lower brainstem.

Several opposite effects of serotonin (<em>5HT</em>) on tumour growth have been reported. On one hand, <em>5HT</em> is known as a growth factor for several types of nontumoural cells, and it has been proposed to take part in the autocrine loops of growth factors contributing to cell proliferation in aggressive tumours such as small cell lung carcinoma. Depending on the tumour type either <em>5HT</em>2 or <em>5HT</em>1 receptor antagonist have been found to inhibit the <em>5HT</em>-induced increase in tumour growth. In contrast, several authors have also reported that <em>5HT</em> and <em>5HT</em>2 agonist can inhibit tumour growth. Most often this effect has been considered to be related with the specific vasoconstrictive effect of <em>5HT</em> or <em>5HT</em>2 agonists on the vessels irrigating the tumour, which has been evidenced by intravital microscopy. Intravital microscopy studies have also shown that vessels perfusing the tumour exhibit a specific vasconstrictive response to <em>5HT</em>1 agonists. In addition, <em>5HT</em> has been shown to be involved in the effects of several anticancer treatments associated with the reduction of tumour flow. Finally, the specific vasoconstrictive effect of <em>5HT</em> or <em>5HT</em> receptor subtype agonists might also be useful in inducing hypoxia in tumours, which could be exploited in a strategy using hypoxia-selective cytotoxins or hypoxia-selective gene therapy.

The distributions of serotonin- (<em>5HT</em>-), substance P- (SP-), small cardioactive peptideb- (SCPb-), and histamine- (HA-) like immunoreactivities were examined in the adult lobster supraesophageal ganglion. Vibratome sections were labeled using avidin-biotin-peroxidase immunocytochemical methods. The localization patterns for each substance were assessed in 21 regions within the median protocerebrum, deutocerebrum, and tritocerebrum. Each immunoreactivity has a unique distribution within the brain; however, most regions are immunoreactive for more than one neurotransmitter. Of particular interest are SP-immunoreactive protocerebral neurons that contact olfactory projection neurons and appear homologous to those found in other crustaceans. Regional differences in immunolabeling within the deutocerebral olfactory and accessory lobes suggest that specific areas within individual olfactory lobe glomeruli serve distinct functions in olfactory processing, and that subpopulations of accessory lobe glomeruli are innervated by different groups of neurons. This detailed comparison of the labeling patterns also has allowed us to define the anatomical connectivity between several cell body clusters, fiber tracts, and neuropil areas in the lobster brain.

RN46A cells are a temperature-sensitive neuronal cell line derived from the E13 rat raphe nucleus. RN46A cells grafted into the adult rat hippocampus and cerebral cortex do not survive beyond 2 weeks. Brain-derived neurotrophic factor (BDNF) regulates the in vitro survival and serotonergic phenotype of RN46A cells, and we hypothesized that expression of BDNF in RN46A cells would potentiate their survival and serotonin (<em>5HT</em>) expression in vivo. The gene encoding rat BDNF was transfected into RN46A cells and the clonal 46A-B14 cell line isolated, 46A-B14 cells synthesize and secrete biologically active BDNF in vitro and synthesize <em>5HT</em> following partial membrane depolarization. Two weeks following 46A-B14 cell transplantation into the adult rat cortex and hippocampus, there is a threefold increase in survival of 46A-B14 cells compared to RN46A cells transfected with the vector alone. The grafted 46A-B14 cells immunohistochemically stain for BDNF and <em>5HT</em>, while RN46A cells transfected with vector only are negative for both BDNF and <em>5HT</em>. In addition, 46A-B14 cells attain more morphologically complex phenotypes, indicating enhanced neuronal differentiation. Autocrine secretion of BDNF by RN46A cells thus potentiates survival and can be used to deliver both BDNF and <em>5HT</em> in vivo.

Neurodevelopmental vulnerability to nicotine extends from fetal stages through adolescence. The recently proposed "sensitization-homeostasis" model postulates that, even in adulthood, nicotine treatment permanently reprograms synaptic activity. We administered nicotine to rats throughout gestation or in adulthood (postnatal days PN90-107), using regimens that reproduce plasma levels in smokers, assessing effects on serotonin (<em>5HT</em>) receptors, the <em>5HT</em> transporter and responses mediated through adenylyl cyclase (AC). Evaluations were then made on PN105, PN110, PN120 and PN180. Prenatal nicotine exposure elicited persistent suppression of <em>5HT</em>1A receptors and upregulation of <em>5HT</em>2 receptors, effects that were selective for males and that first emerged in young adulthood. In addition, AC activity was reduced and there was uncoupling of receptor-mediated responses. With nicotine exposure restricted to adulthood, there were few changes in <em>5HT</em> synaptic proteins during treatment or in the first 2 weeks post-treatment, distinctly different from the robust alterations seen earlier with similar nicotine regimens given in adolescence. Nevertheless, there was long-term upregulation of the proteins in males at 6 months of age; females were unaffected. Exposure to prenatal nicotine followed by adult nicotine overcame the protection of females, so that they, too showed long-term effects not seen with either treatment alone; the effects in males were exacerbated in an additive manner. Our results indicate that the effects of nicotine during prenatal or adolescent stages are indeed distinct from the effects in adults, but that even adults show persistent changes after nicotine exposure, commensurate with the sensitization-homeostasis model. These effects may contribute to lifelong vulnerability to readdiction.

The high-affinity states of dopamine D2 and D3 receptors, serotonin <em>5HT</em>-2A receptors, beta-2-adrenoceptors, alpha-1 and alpha-2 adrenoceptors, opiate receptors, and muscarinic receptors were inhibited by clinical concentrations of anesthetics, including isoflurane, halothane, chloral hydrate, ketamine, and ethanol. The inhibition occurred not only in vitro, but also in vivo in rats anesthetized with isoflurane, with the high-affinity states recovering at different rates. Because the high-affinity states of G-protein-linked receptors are physiologically functional, their general inhibition by clinical concentrations of anesthetics may underlie general anesthesia and may explain some of the side effects of anesthetics. Subanesthetic concentrations of the anesthetics, including ketamine, stimulated the incorporation of GTP into the cloned dopamine D2 receptors. It is possible that the classical stage 2 excitement phase which occurs with subanesthetic concentrations of general anesthetics and ketamine may be associated with this general stimulation of a variety of G-protein-linked receptors, as found in the present study, while the stage 3 level of surgical anesthesia may be associated with the inhibition of the high-affinity states of several receptors.

Selective serotonin reuptake inhibitors are the most widely prescribed drugs targeting the CNS with acute and chronic effects in cognitive, emotional and behavioral processes. This suggests that microcircuits of the human cerebral cortex are powerfully modulated by selective serotonin reuptake inhibitors, however, direct measurements of serotonergic regulation on human synaptic interactions are missing. Using multiple whole-cell patch-clamp recordings from neurons in acute cortical slices derived from nonpathological human samples of the prefrontal cortex, we show that neuronal assemblies triggered by single action potentials of individual neurons in the human cortex are suppressed by therapeutic doses of fluoxetine (Prozac). This effect is boosted and can be mimicked by physiological concentrations of serotonin through <em>5HT</em>-2A and <em>5HT</em>-1A receptors. Monosynaptic excitatory connections from pyramidal cells to interneurons were suppressed by application of serotonin leaving the monosynaptic output of GABAergic cells unaffected. Changes in failure rate, in paired-pulse ratio, and in the coefficient of variation of the amplitude of EPSPs suggest a presynaptic action of serotonin. In conclusion, activation of neuronal assemblies, which were suggested as building blocks of high order cognitive processes, are effectively downregulated by the acute action of selective serotonin reuptake inhibitors or serotonin at the site of pyramidal output in human microcircuits.

Childhood neurodevelopmental disorders like Angelman syndrome and autism may be the result of underlying defects in neuronal plasticity and ongoing problems with synaptic signaling. Some of these defects may be due to abnormal monoamine levels in different regions of the brain. Ube3a, a gene that causes Angelman syndrome (AS) when maternally deleted and is associated with autism when maternally duplicated has recently been shown to regulate monoamine synthesis in the Drosophila brain. Therefore, we examined monoamine levels in striatum, ventral midbrain, frontal cerebral cortex, cerebellar cortex and hippocampus in Ube3a deficient and Ube3a duplication animals. We found that serotonin (<em>5HT</em>), a monoamine affected in autism, was elevated in the striatum and cortex of AS mice. Dopamine levels were almost uniformly elevated compared to control littermates in the striatum, midbrain and frontal cortex regardless of genotype in Ube3a deficient and Ube3a duplication animals. In the duplication 15q autism mouse model, paternal but not maternal duplication animals showed a decrease in <em>5HT</em> levels when compared to their wild type littermates, in accordance with previously published data. However, maternal duplication animals show no significant changes in <em>5HT</em> levels throughout the brain. These abnormal monoamine levels could be responsible for many of the behavioral abnormalities observed in both AS and autism, but further investigation is required to determine if any of these changes are purely dependent on Ube3a levels in the brain.

Previously, d-lysergic acid diethylamide was found to have a more powerful inhibitory action upon serotonergic (raphe) neurons than upon neurons in areas receiving an identified serotonergic input (e. g., amygdala, ventral lateral geniculate). In the present studies, using microiontophoretic techniques, the relative potencies of 3 indoleamine hallucinogens, psilocin, DMT, and bufotenine were tested upon <em>5HT</em> neurons in the raphe (presynaptic neurons) and postsynaptic neurons in the ventral lateral geniculate and amygdala of the rat. Psilocin showed the greatest preferential inhibitory effect upon raphe as compared to postsynaptic neurons. DMT was intermdeiate and bufotenine had the least differential activity. This rank ordering correlates with the relative hallucinogenic potencies of these compounds: psilocin greater than DMT greater than bufotenine. The results support the hypothesis that low doses of indoleamine halluciogens act preferentially upon presynaptic serotonin receptors to inhibit raphe neurons, thus releasing postsynaptic neurons from a tonic inhibitory serotonergic influence.