The present study investigated the effect on the rat's eating behavior of the new selective <em>5HT</em>2 antagonist ritanserin. The results obtained indicate that: single subcutaneous (SC) injection of ritanserin, at doses between 0.1 and 1 mg/kg b.wt., neither elicits food intake in sated rats, nor increases the intake induced by food deprivation; subchronic SC treatment (15 days) with 0.1 mg/kg does not increase food intake nor body weight gain; subchronic SC treatment with high doses, 1 or 10 mg/kg, produces small and transient increases in food intake without affecting body weight gain. When ritanserin was tested for its ability to block the anorectic effect of exogenous <em>5HT</em>, it inhibited the effect of intraperitoneal (IP) <em>5HT</em>, but proved to be completely inactive versus the effect of <em>5HT</em> injected into the hypothalamic paraventricular nucleus, which is highly sensitive to this effect of <em>5HT</em>. This last finding suggests that the anorectic action of central endogenous <em>5HT</em> is also not blocked by ritanserin, thus proposing a reasonable explanation for the absence of orexigenic effect following its administration. Moreover, it suggests that in rats the hypothalamic receptors mediating the effect of <em>5HT</em> on eating behavior are different from the <em>5HT</em>2 of the frontal cortex which have been shown to be completely blocked by ritanserin under the experimental conditions employed in our study.

Affinities and densities of binding sites for the <em>5HT</em>1A receptor ligand [3H]8-hydroxy(di-n-propylamino)tetralin ([3H]8-OH-DPAT) and the <em>5HT</em>2 receptor ligand [3H]ketanserin were measured using a rapid filtration assay in crude membrane preparations from frontal cortex and hippocampus of nine cirrhotic patients who died in hepatic encephalopathy and from an equal number of age-matched subjects free from hepatic, neurological or psychiatric disorders. Binding site densities (Bmax) obtained by Scatchard analysis of saturation binding isotherms for [3H]8-OH-DPAT were decreased in frontal cortex (by 56%, P < 0.05) and hippocampus (by 30%, P < 0.05). [3H]ketanserin binding sites were concomitantly increased (by 55%, P < 0.05) in hippocampus of cirrhotic patients. Ligand binding affinities were within normal ranges in all cases. Previous reports have described the accumulation of the <em>5HT</em> metabolite 5-hydroxyindoleacetic acid and increased activities of the <em>5HT</em>-metabolizing enzyme MAOA in this same material from patients with hepatic encephalopathy. Taken together, these findings suggest that alterations of serotoninergic function in brain could be responsible for some of the neuropsychiatric symptoms of hepatic encephalopathy observed in humans with chronic liver disease.

The effect of short-term (15 days) and long-term (60 days) ethanol treatment and withdrawal on agonist-stimulated phosphoinositide (Pl) hydrolysis, serotonin receptor subtypes (<em>5HT</em>1A and <em>5HT</em>2), and alpha 1-adrenergic receptors were studied in rat cerebral cortex. Short-term ethanol treatment had no significant effect on serotonin (<em>5HT</em>), norepinephrine (NE), and calcium ionophore (A23187)-stimulated [3H]-inositol-1-phosphate ([3H]-IP1) formation and 5-HT2 receptors as measured by 125I-lysergic acid diethylamide (125I-LSD) binding, in rat cerebral cortex. However, 15 days of ethanol treatment, followed by 24 hr of withdrawal resulted in a decrease in Bmax of 125I-LSD binding without significant change in KD, as well as a decrease in <em>5HT</em>-stimulated [3H]-IP1 formation in rat cerebral cortex. <em>5HT</em>1A and alpha 1-adrenergic receptors were determined by using [3H]-8-hydroxy-2-(di-N-propylamino)tetralin and [3H]-prazosin as radioligand, respectively. We also observed that long-term ethanol treatment had no significant effect on Bmax and KD of <em>5HT</em>2, <em>5HT</em>1A, and alpha 1-adrenergic receptors, as well as NE and A23187-stimulated [3H]-IP1 formation, but significantly decreased the <em>5HT</em>-stimulated [3H]-IP1 formation in rat cerebral cortex. It is possible that a decrease in <em>5HT</em>-induced PI turnover after long-term ethanol exposure may be due to a decrease in coupling of <em>5HT</em>2 receptors to G protein or PLC enzyme, whereas the decrease in <em>5HT</em>-induced PI turnover after withdrawal may be due to a decrease in functional <em>5HT</em>2 receptor number.

Neuromodulatory systems such as noradrenaline (NE), acetylcholine (ACh), and serotonin (<em>5HT</em>) serve important functions in sensory perception. We use the olfactory bulb (OB) as a model system to study the roles of individual neuromodulators in sensory perception. Using a spontaneous, nonreward motivated detection task, as well as a reward-motivated task, we show that rats can easily respond to odorants at very low concentrations when motivated to do so in a food-rewarded task, despite not showing spontaneous responses to these low concentration odorants. Using the same tasks paired with local bulbar infusions of noradrenergic and cholinergic drugs, we then show that rats engage their noradrenergic, but not their cholinergic system, to better respond to near threshold odorants. These results suggest that while cholinergic modulation of OB function is mostly important for odor decorrelation and discrimination, noradrenergic modulation is important for signal-to-noise modulation.

We have studied the regulation of human platelet activation by cyclic AMP (cAMP), and the cyclooxygenase products by examining the effect of prostacyclin (PGI2) and indomethacin on platelet aggregation, release reaction and thromboxane B2 (TxB2) generation induced by the full dose range of common platelet agonists in both platelet-rich plasma and washed platelets. Platelet aggregation, [14C]-<em>5HT</em> and TxB2 release induced by "threshold" and "supramaximal" concentrations of ADP, adrenaline, platelet-activating factor (PAF) and U46619 were totally abolished by low concentrations of PGI2 (3-6 nM). In contrast, platelet activation induced by submaximal concentrations of collagen, thrombin and the calcium ionophore A23187 was only partially inhibited by PGI2 (3-3000 nM). PAF-induced release reaction like that induced by ADP and adrenaline was totally dependent on the cyclooxygenase products and aggregation, while U46619-induced release reaction was only partially dependent on aggregation and the cyclooxygenase products. While both PGI2 (18-3000 nM) and indomethacin (10 microM) abolished collagen-induced aggregation and the aggregation-mediated release reaction, neither inhibitor significantly inhibited platelet adhesion or the adhesion-mediated release reaction. Maximal thrombin-induced aggregation and release reaction was also not significantly inhibited by PGI2 (300 nM) or indomethacin (10 microM). Thromboxane (TxB2) generation induced by sub-maximal to maximal concentrations of collagen, thrombin and A23187 was, although significantly inhibited, not abolished by PGI2. These results demonstrate that PAF is a "weak" agonist similar to ADP and adrenaline, U46619 is an agonist intermediate between weak and strong which induces a release reaction that is only partially dependent on aggregation, but unlike the strong agonists, is totally susceptible to inhibition by PGI2, PGI2 is an indirect inhibitor of phospholipase activation, which does not significantly inhibit non-aggregation-mediated arachidonate mobilization, induced by the strong agonists, and the so-called third pathway in the collagen and thrombin-induced release reaction, which is insensitive to indomethacin, is also insensitive to elevators of cAMP such as PGI2.

The interaction of heavy metals (HgCl2, CdCl2, CuCl2, PbCl2 and ZnCl2) and neurotransmitters (ACh, <em>5HT</em> and DA) was studied on the excitable membrane of identified neurons of Lymnaea stagnalis and Helix pomatia. It was shown that, (1) The excitability and chemosensitivity of molluscan neurons were modified under the influence of the heavy metals Hg(2+), Cd(2+), Cu(2+), Pb(2+) and Zn(2+). (2) Change in excitability to transmitters occurred as a potentiation or depression of the evoked response both in duration of membrane polarization and in frequency of spike activity. (3) The chemosensitivity changes in various ways, namely: excitatory effect was totally eliminated; one component of the effect was depressed. Different neurons may show different reactions to the same heavy metal. (4) There were differences in the effects of various heavy metals. Hg(2+) has a more generalized effect than Cd(2+); Cu(2+), Pb(2+) and Zn(2+) were less effective in a number of neurons. The heavy metal effect was dose dependent, too. (5) Both inward and outward currents, which were evoked by neurotransmitters or voltage induced, were modified in most of the tested neurons. Both an increase and decrease of the membrane permeability occurred in different neurons in response to the same or different heavy metals. (6) The changes can be interpreted as a result of direct effect on specific ionic channels; modification of receptors binding ACh, <em>5HT</em>, or DA; modification of intracellular processes responsible for the regulation of membrane permeability.

Specific binding of [3H]spiperone and [3H]domperidone, displaceable by 1 microM d-butaclamol, was examined in rat striatal membranes. Initial saturation and displacement experiments indicated that [3H]spiperone bound to more sites than [3H]domperidone and that, whilst all displacing drugs were more potent against [3H]domperidone, this difference in potency was greatest for dopamine agonists and specific antagonists and least for <em>5HT</em>-related drugs. Sulpiride displaced [3H]spiperone biphasically, and was used at a concentration of 50 microM to examine two classes of [3H]spiperone binding: site 1 displaceable by sulpiride, and site 2 displaceable by butaclamol but not by sulpiride. Site 1 had twice the capacity of site 2 and ten times the affinity for [3H]spiperone. Dopaminergic drugs displaced preferentially from site 1, whilst <em>5HT</em>-related drugs were more potent against site 2. GTP reduced the potency of dopamine, noradrenaline and, to a lesser extent, <em>5HT</em> at site 1, but had no effect at site 2. [3H]Domperidone sites had the same capacity as [3H]spiperone site 1, and dopamine, noradrenaline and <em>5HT</em>, in the absence or presence of GTP, and sulpiride had essentially identical affinities for [3H]domperidone sites and [3H]spiperone site 1. It is concluded that [3H]domperidone and [3H]spiperone label an identical population of dopamine (D2) receptors, whilst [3H]spiperone also labels a substantial number of non-dopamine sites, at least some of which are <em>5HT</em>-related. [3H]spiperone also labels a substantial number of non-dopamine sites, at least some of which are <em>5HT</em>-related. [3H]Domperidone is the better radioligand for dopamine receptors.

Stimulation of platelets with the ionophore A23187, thrombin, ADP or PAF-acether resulted in a rapid increase of cytosolic free Ca2+, as measured with Quin-2, and in aggregation, <em>5HT</em> secretion and - in the case of the first two agonists - thromboxane generation. PGI2 and dibutyryl cyclic AMP inhibited all these responses, except in the case of A23187, in response to which the increase in Ca2+ was unaffected, although the other responses were inhibited. The inhibition of aggregation and secretion in response to the combination of thrombin and A23187 was indistinguishable from that in response to thrombin alone. It thus appears that cAMP inhibits these responses independently of its effect in lowering cytosolic free Ca2+.

Rabbit bladder body was stimulated to contract by a number of agonists, of which bradykinin was the most potent, and ATP one of the least potent substances tested. The atropine-resistant component of the neurogenic response was unaffected by 2 X 10(-5) M chlorpheniramine or 10(-6) M methysergide, doses which suppressed responses to histamine or <em>5HT</em>. Indomethacin 10(-5) M, or 10(-5) M capsaicin both reduced the atropine-resistant component. Following treatment with 10(-6) M atropine and 10(-5) M prazosin, 10(-4) M ANAPP3 produced a further suppression of the response, but did not antagonize the response to ATP. In the bladder body, the transmitter(s) responsible for the neurogenic response may be acetylcholine and prostaglandins and possibly ATP and substance P.

The concentrations of dopamine (DA) norepinephrine (NE), serotonin (<em>5HT</em>) and their metabolites, HVA, DOPAC, MHPG-SO4 and 5HIAA were measured in several brain areas of rats aged 4, 18 and 29 months. Dopamine and its metabolites showed a decline, statistically correlated with age, in all the dopaminergic areas considered, indicating that this system is profoundly affected in the senescent rat. The changes in the noradrenergic system were more complex. This neurotransmitter was reduced in spinal cord and in limbic area, but was not modified in hippocampus, cerebellum, striatum and s. nigra. In cortex, MHPG-SO4, the main NE metabolite, showed a significantly age-related increase. Tyrosine hydroxylase (TH) activity was low in striatum, and brainstem but not in hypothalamus of aged rats. Neither <em>5HT</em> nor its metabolites was affected by age. The results indicate that central catecholaminergic systems are markedly affected in senescent rats.

Previously we reported that cultured endothelial cells (ECs) can promote or inhibit polymorphonuclear leukocyte (PMN) diapedesis and albumin permeability in vitro by altering monolayer intercellular integrity (an activity influenced by pretreatment with exogenous amines). Endothelial eicosanoid release was also seen to stimulate both PMN motility and diapedesis. We now demonstrate that these endothelial activities are related. Thromboxane (Tx) B2 pretreatment of ECs results in increased diapedesis and permeability across the monolayers whereas 6-keto-PGF1 alpha pretreatment has the opposite effects, demonstrating that these eicosanoids exert direct effects upon ECs, in addition to their direct effects upon PMNs as previously described. Norepinephrine (NE) or serotonin (<em>5HT</em>) pretreatment of ECs inhibits the release of TxB2 and 6-keto-PGF1 alpha, with the result that the stimulation of PMN motility by these EC metabolites is eliminated. In contrast, histamine increases the endothelial release of eicosanoids, resulting in a further increase in PMN motility. We conclude that histamine directly reduces EC monolayer integrity (by altering the endothelial cytoskeleton) and also increases eicosanoid release, actions which both enhance PMN motility and further reduce monolayer integrity. Conversely, NE and <em>5HT</em> both increase intercellular integrity and decrease eicosanoid release, thereby decreasing PMN motility, diapedesis, and albumin permeability.

Aggression control has been investigated across species and is centrally mediated within various brain regions by several neural systems that interact at different levels. The debate over the degree to which any one system or region affects aggressive responding, or any behavior for that matter, in some senses is arbitrary considering the plastic and adaptive properties of the central nervous system. Nevertheless, from the reductionist point of view, the compartmentalization of evolutionarily maladaptive behaviors to specific regions and systems of the brain is necessary for the advancement of clinical treatments (e.g., pharmaceutical) and novel therapeutic methods (e.g., deep brain stimulation). The general purpose of this chapter is to examine the confluence of two such systems, and how their functional interaction affects aggressive behavior. Specifically, the influence of the serotonin (<em>5HT</em>) and arginine vasopressin (AVP) neural systems on the control of aggressive behavior will be examined individually and together to provide a context by which the understanding of aggression modulation can be expanded from seemingly parallel neuromodulatory mechanisms, to a single and highly interactive system of aggression control.

Ciliary neurotrophic factor (CNTF) is a multifunctional cytokine that mediates survival and differentiation of neurons as well as many other cell types. In this study, CNTF and leukemia inhibitory factor (LIF) reduced the apparent number of primary serotonergic neurons in E14 raphe culture by 90% as determined by immunocytochemistry for serotonin (<em>5HT</em>). The reduction in <em>5HT</em> cell number was not due to neuronal loss as removal of CNTF after 4 days in culture resulted in a partial restitution of the serotonergic phenotype. In the RN46A serotonergic cell line which is induced to become serotonergic by brain-derived neurotrophic factor (BDNF), the addition of CNTF suppressed tryptophan hydroxylase and <em>5HT</em> synthesis and increased choline acetyl transferase (ChAT) expression by 6-fold and ChAT activity by 20- to 30-fold over 12 days. As with the primary neurons, removal and replacement of CNTF with BDNF after 4 days resulted in a partial restitution of <em>5HT</em> expression. Moreover, other members of the CNTF-cytokine family that use gp130 and/or LIF receptor beta as their signal transducing receptors-LIF, oncostatin M, interleukin 6, and interleukin 11-had similar effects on increasing ChAT activity and reducing <em>5HT</em> expression in RN46A cells. Analysis of <em>5HT</em> levels showed no significant difference in the amount of serotonin between wild-type and CNTFR alpha knockout mice at birth, suggesting that the potential to switch phenotype mediated through CNTFR alpha is a latent property of neuroepithelial precursors in the raphe nucleus.

We determined the effects of serotonin (<em>5HT</em>; 6 concentrations ranging from 0.005 to 500 microM) pressure microinjection into the hypoglossal (XII) motor nucleus (100-500 nl; pH = 7.2-7.4) on XII whole nerve activity and reflex response to upper airway negative pressure in 15 decerebrated, vagotomized, paralyzed and artificially ventilated cats. Increasing <em>5HT</em> concentration resulted in a concentration dependent increase in ipsilateral tonic XII activity, with no change in phasic XII activity. Threshold concentrations ranged from 0.005 to 0.5 microM, with the maximal response reached at 5 microM. Increasing <em>5HT</em> concentration also increased the duration of the XII response. This ranged from 50 s with 0.5 microM, to over 10 min with 500 microM <em>5HT</em>. However, <em>5HT</em> did not significantly change the XII whole nerve reflex response to upper airway negative pressure (-20 cm H2O) at any <em>5HT</em> concentration (n = 5). All <em>5HT</em> effects were reversed by microinjection of 1.0 mM methysergide. We conclude that XII responses to <em>5HT</em> are elicited at low concentrations of <em>5HT</em>, which have a relatively short duration of effect, but that <em>5HT</em> at the XII motor nucleus has no effect on the XII reflex response to upper airway negative pressure.

We have determined the effects of ketanserin, a <em>5HT</em>2 antagonist, and of mepyramine, a histamine H1 antagonist, on the aggregation induced in platelet rich plasma by 5-hydroxytryptamine (<em>5HT</em>), adenosine diphosphate (ADP), and by combinations of <em>5HT</em> and ADP. Both ketanserin and mepyramine inhibited <em>5HT</em>-induced aggregation and the <em>5HT</em> component of the aggregation induced by combinations of <em>5HT</em> and ADP. Both agents also inhibited the second phase of the aggregation induced by ADP alone but higher concentrations of the agents were required. On a molar basis, ketanserin was always a more potent inhibitor of aggregation than mepyramine. Ketanserin did not consistently inhibit the ADP-induced release reaction nor did it inhibit ADP-induced aggregation in aspirin-treated platelets that were unable to undergo a release reaction. The results suggest that <em>5HT</em>2 receptors are involved in <em>5HT</em>-induced aggregation and that the platelets' endogenous <em>5HT</em> may contribute to the second phase of ADP-induced aggregation. We have also compared the effects of ketanserin and mepyramine on <em>5HT</em> uptake into platelets. In this case mepyramine was a much more potent inhibitor than ketanserin. The different effectiveness of ketanserin and mepyramine as inhibitors of aggregation and <em>5HT</em> uptake provides further evidence for different <em>5HT</em> receptors for these two processes, and indicates that those involved in the <em>5HT</em> uptake may be more akin to histamine H1 receptors.

Involvement of <em>5HT</em>2 receptors in human platelet aggregation was assessed by studying the effect of ADP, epinephrine and thrombin on 3H-<em>5HT</em> release from platelets. The release experiments were made with a perfusion method to preserve any compound, released or formed by platelet, from interacting with platelet itself. In these conditions, aggregation does not occur, as confirmed by Scanning Electron Microscopy. These release experiments showed that the platelet activation by such agents is coupled with 5-HT release. The aggregation experiments, made on different aliquots of the same platelet-rich plasma (PRP), showed that the released 5-HT, interacting with its own receptors on platelet activated surface, determines aggregation. In fact, although it is known that 5-HT added to PRP was only able to induce a moderate platelet aggregation, the 5-HT2 antagonist ketanserin counteracted the aggregation induced by ADP, epinephrine and thrombin. These results suggest that a <em>5HT</em>2 antagonist could be therapeutically important in those pathological states in which serotonin, released by activated platelets, may increase aggregation.

The Anorexia (anx) mutation causes reduced food intake in preweanling mice, resulting in death from starvation within 3-4 weeks. We have found serotonin (<em>5HT</em>) hyperinnervation in the anx brain; altered noradrenergic (NE) innervation may also mediate eating disorders. We examined the expression of synthetic or catabolic monoamine enzyme genes in brainstem nuclei: serotonin transporter (<em>5HT</em>T) and monoamine oxidase A (MAOA) in the raphe nuclei (RN), and MAOA, norepinephrine transporter (NET), and tyrosine hydroxylase (TH) in the locus ceruleus (LC). We compared 3-week old anx with control and 24-h food-deprived wildtype littermates using in situ hybridization to measure mRNA levels by quantitative autoradiography. The anx mutation was correlated with decreased MAOA mRNA in the LC (but not RN), decreased <em>5HT</em>T mRNA in the RN, and a trend towards lower NET mRNA in the LC. Food deprivation decreased MAOA mRNA in the LC (but not RN), increased TH mRNA in the LC, and did not alter NET or <em>5HT</em>T mRNA levels. Thus, the effect of the anx mutation on MAOA expression in the LC paralleled the effect of food-deprivation, but the anx mutation and food-deprivation had differential effects on the expression of TH, NET, and <em>5HT</em>T genes. Decreased <em>5HT</em>T expression in the anx RN is consistent with upregulation of serotonergic neurotransmission that may accompany <em>5HT</em> hyperinnervation. Central NE levels or innervation may be altered in anx mice by decreased expression of NET and MAOA and a lack of TH upregulation induced by food deprivation as in wild-type mice.

Changes in hypothalamic concentration and turnover index (TI) of norepinephrine (NE), dopamine (DA), and serotonin (<em>5HT</em>) were studied during the first estrous cycle at the onset of puberty. Rats were killed when 40% of the population showed open vaginas. They were classified according to the state of their reproductive tract and serum LH values, as in anestrus, early proestrus, late proestrus, estrus, or diestrus. Serum LH, PRL, and hypothalamic LHRH were measured by RIA. The TIs for DA and NE were measured by estimating their rate of decrease after administration of alpha-methyl-para-tyrosine, and for <em>5HT</em>-TI by its increase after pargyline administration. An increase in NE-TI in the hypothalamus was observed between anestrus and early proestrus, a decrease in DA-TI during early and late proestrus, and a small increase in <em>5HT</em>-TI between early and late proestrus. LH and PRL peaks were observed at late proestrus when DA-TI and NE-TI reached their lowest values and hypothalamic LHRH concentration was failing. After late proestrus, the DA-TI rose sharply, NE-TI remained essentially unchanged. <em>5HT</em>-TI fell, and serum LH and PRL declined to basal levels. These results suggest that the LH and PRL surges at late proestrus during the first estrous cycle at puberty are associated with an increase in NE-TI at early proestrus, a progressive decline in DA-TI at early and late proestrus, and an increase in <em>5HT</em>-TI at late proestrus.

The aim of the present study was to investigate the binding sites interactions and the selectivity of sarpogrelate to human 5-HT(2) receptor family (5-HT(2A), 5-HT(2B) and 5-HT(2C) receptor subtypes) using molecular modeling. Rhodopsin (RH) crystal structures were used as template to build structural models of the human serotonin-2A and -2C receptors (5-HT(2A)R, 5-HT(2C)R), whereas for 5-HT(2B)R, we used our previously published three-dimensional (3D) models based on bacteriorhodopsin (BR). Sarpogrelate, a novel 5-HT(2)R antagonist, was docked to the receptors. Molecular dynamics (MD) simulations produced the strongest interaction for 5-HT(2A)R/sarpogrelate complex. Upon binding, sarpogrelate constraints aromatic residues network (Trp(3.28), Phe(5.47), Trp(6.48), Phe(6.51), Phe(6.52) in 5-HT(2A)R; Phe(3.35), Phe(6.51), Trp(7.40) in 5-HT(2B)R; Trp(3.28), Phe(3.35), Phe(5.47), Trp(6.48), Phe(6.51), Phe(6.52) in 5-HT(2C)R) in a stacked configuration, preventing activation of the receptor. The models suggest that the structural origin of the selectivity of sarpogrelate to 5-HT(2A)R vs both 5-HT(2B)R and 5-HT(2C)R comes from the following results: (1) The tight interaction between the antagonist and the transmembrane domain (TMD) 3. Asp(3.32) neutralizes the cationic head and interacts simultaneously with carboxylic group hydrogen of the antagonist molecule. (2) Due to steric hindrance, Ser(5.46) (vs Ala(5.46) in <em>5HT</em>(2B) and <em>5HT</em>(2C)) prevents sarpogrelate to enter deeply inside the hydrophobic core of the helix bundle and to interact with Pro(5.50). (3) The side chain of Ile(4.56) (vs Ile(4.56) in <em>5HT</em>(2B)R and Val(4.56) in <em>5HT</em>(2C)R) constraints sarpogrelate to adjust its position by translating toward the strongly attractive Asp(3.32). These results are in good agreement with binding affinities (pKi) of sarpogrelate for 5-HT(2) receptor family expressed in transfected cell.

The effect of progesterone (P) on monoamine levels and turnover was evaluated in 8 brain nuclei in estrogen-primed rats. Animals were subcutaneously (SC) injected with P or vehicle 21 hours after SC treatment with 5 micrograms of estradiol benzoate (EB). EB-primed animals treated with P showed high levels of lordosis behavior and an LH surge three hours later. Initial concentrations of norepinephrine (NE), dopamine (DA), serotonin (<em>5HT</em>) and 5-hydroxyindole acetic acid were determined in EB-saline treated controls 3 hours after P or vehicle. NE and DA turnover was estimated from the exponential decline of these amines 2 hours after IP injection of alpha-methyl-p-tyrosine (5 hours after P or vehicle). The accumulation of <em>5HT</em> 20 min following IP injection of pargyline was used as an index of <em>5HT</em> turnover. P did not affect the initial NE, <em>5HT</em> or 5HIAA concentrations in any of the brain nuclei studied, but decreased DA content in the arcuate-median eminence region (Ar-ME). The DA rate constant was elevated in the nucleus of the diagonal band of Broca and the DA turnover rate was decreased in the Ar-ME. In the periventricular region (PVE, anterior hypothalamic level) the NE turnover rate (K, pg/microgram protein/hr) and rate constant (k, hr-1) decreased following P treatment. Progesterone treatment decreased the accumulation of <em>5HT</em> in the ventromedial hypothalamus (VMN, pars lateralis) and the dorsal midbrain central grey (MCG). Progesterone effects on monoamine turnover were not found in the lateral septal, medial preoptic, anterior hypothalamic or dorsal raphe nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are first-line treatments for posttraumatic stress disorder (PTSD). Serotonergic (<em>5HT</em>) attenuation of stress sensitivity is postulated from SSRIs' effects in other anxiety disorders, and we studied this in PTSD.

METHODS

Ten patients with PTSD fully recovered on SSRIs (Clinical Global Impression Scale-I 1 and 2) were enrolled in the study. Patients were tested on two occasions 1 week apart; in each session, they received a drink containing large neutral amino acids (LNAAs) either with (sham tryptophan depletion [STD], control) or without (acute tryptophan depletion [ATD]) tryptophan. At 5.5 hours after the drink, subjects were exposed to a trauma-related exposure challenge. Self-reports of PTSD (visual analogue scales [VAS] and the Davidson Trauma Scale [DTS]), anxiety (Spielberger State Inventory [STAI] Form Y-1), and mood (Profile of Mood States [POMS]) were obtained. Heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure were also measured.

RESULTS

The trauma-related exposure challenge induced anxiety on both days, with more marked responses on the ATD day according to VAS, DTS, POMS, and DBP (p < .05). A trend of significance (.1>> p>> .05) was observed for STAI Form Y-1, HR, and SBP.

CONCLUSIONS

These data demonstrate that ATD accentuates responses to trauma-related stimuli in SSRI-recovered PTSD. They also suggest that SSRI-induced increases in serotonin function restrain PTSD symptoms, especially under provocation, supporting a role for serotonin in mediating stress resilience.

Xenopus oocytes were used to examine the coupling of the serotonin 1c (<em>5HT</em>1c) and thyrotropin-releasing hormone (TRH) receptors to both endogenous and heterologously expressed G protein alpha subunits. Expression of either G protein-coupled receptor resulted in agonist-induced, Ca(2+)-activated Cl- currents that were measured using a two-electrode voltage clamp. <em>5HT</em>-induced Cl- currents were reduced 80% by incubating the injected oocytes with pertussis toxin (PTX) and inhibited 50-65% by injection of antisense oligonucleotides to the PTX-sensitive Go alpha subunit. TRH-induced Cl- currents were reduced only 20% by PTX treatment but were inhibited 60% by injection of antisense oligonucleotides to the PTX-insensitive Gq alpha subunit. Injection of antisense oligonucleotides to a novel Xenopus phospholipase C-beta inhibited the <em>5HT</em>1c (and Go)-induced Cl- current with little effect on the TRH (and Gq)-induced current. These results suggest that receptor-activated Go and Gq interact with different effectors, most likely different isoforms of phospholipase C-beta. Co-expression of each receptor with seven different mammalian G protein alpha subunit cRNAs (Goa, Gob, Gq, G11, Gs, Golf, and Gt) was also examined. Co-expression of either receptor with the first four of these G alpha subunits resulted in a maximum 4-6-fold increase in Cl- currents; the increase depended on the amount of G alpha subunit cRNA injected. This increase was blocked by PTX for G alpha oa and G alpha ob co-expression but not for G alpha q or G alpha 11 co-expression. Co-expression of either receptor with Gs, Golf, or Gt had no effect on Ca(2+)-activated Cl- currents; furthermore, co-expression with Gs or Golf also failed to reveal <em>5HT</em>- or TRH-induced changes in adenylyl cyclase as assessed by activation of the cystic fibrosis transmembrane conductance regulator Cl- channel. These results indicate that in oocytes, the <em>5HT</em>1c and TRH receptors do the following: 1) preferentially couple to PTX-sensitive (Go) and PTX-insensitive (Gq) G proteins and that these G proteins act on different effectors, 2) couple within the same cell type to several different heterologously expressed G protein alpha subunits to activate the oocyte's endogenous Cl- current, and 3) fail to couple to G protein alpha subunits that activate cAMP or phosphodiesterase.

Axotomy elicits changes in gene expression, but little is known about how information from the site of injury is communicated to the cell nucleus. We crushed nerves in Aplysia californica and the sciatic nerve in the mouse and found short- and long-term activation of an Elk1-SRF transcription complex that binds to the serum response element (SRE). The enhanced short-term binding appeared rapidly and was attributed to the injury-induced activation of an Elk1 kinase that phosphorylates Elk1 at ser383. This kinase is the previously described Aplysia (ap) ERK2 homologue, apMAPK. Nerve crush evoked action potentials that propagated along the axon to the cell soma. Exposing axons to medium containing high K(+), which evoked a similar burst of spikes, or bathing the ganglia in 20 microM serotonin (<em>5HT</em>) for 20 min, activated the apMAPK and enhanced SRE binding. Since <em>5HT</em> is released in response to electrical activity, our data indicate that the short-term process is initiated by an injury-induced electrical discharge that causes the release of <em>5HT</em> which activates apMAPK. <em>5HT</em> is also released in response to noxious stimuli for aversive learning. Hence, apMAPK is a point of convergence for injury signals and learning signals. The delay before the onset of the long-term SRE binding was reduced when the crush was closer to the ganglion and was attributed to an Elk1 kinase that is activated by injury in the axon and retrogradely transported to the cell body. Although this Elk1 kinase phosphorylates mammalian rElk1 at ser383, it is distinct from apMAPK.

It has been shown in various studies that increase in serotonergic neurotransmission is associated with increased memory consolidation whereas low brain <em>5HT</em> impairs memory performance. In the first phase of our study we found that tryptophan (TRP) administration for 6 weeks increased plasma TRP and whole brain TRP, <em>5HT</em> and 5HIAA levels. Many brain regions are involved in the learning process but particularly the hippocampus is known to have key role in learning and memory. The present study was therefore designed to investigate the effects of TRP loading particularly on hippocampal <em>5HT</em> metabolism and cognitive performance in rats. TRP-treated rats demonstrated spatial enhancement as evidenced by a significant decrease in time to find the hidden food reward in radial arm maze test (RAM). The important finding of the present study was the greater increase in the <em>5HT</em> metabolism in hippocampus than in any other brain region of the TRP-treated rats. This increased <em>5HT</em> metabolism in the hippocampus emphasizes the involvement of this region in memory process.