Chronic fluoxetine treatment upregulates 5-HT uptake sites and 5-HT2 receptors in rat brain: An autoradiographic study

This study was undertaken to investigate the effect of chronic treatment with fluoxetine, a selective serotonin uptake inhibitor used widely in the treatment of depression, on the distribution and density of 5-HT uptake sites, 5-HT₂ receptors, and vesicular amine uptake sites in rat brain. Fluoxetine (10 mg/kg i. p.) was administered daily for 21 days. The density of 5-HT uptake sites labelled by [³H]paroxetine, 5-HT₂ receptors labelled by [³H]ketanserin in presence of tetrabenazine and vesicular amine uptake sites labelled by [³H]ketanserin in the presence of mianserin were measured by quantitative autoradiography in 22 areas of rat brain, using coronal tissue sections. Chronic administration of fluoxetine produced significant increases in the density of 5-HT uptake sites in layers of frontoparietal cortex (by 32–43%), of striate cortex (by 55%), in CA1 field of hippocampus (by 111%) and in superior colliculus (by 20%). Fluoxetine treatment also resulted in upregulation of 5-HT₂ receptors in layers of frontparietal cortex (31–38%) and in CA2-3 fields of hippocampus (by 39%). The density of tetrabenazine-sensitive vesicular amine uptake sites in the caudate-putamen was also significantly increased (by 66%). The observed alterations in 5-HT uptake site and 5-HT₂ receptor densities are likely a part of adaptive neuronal changes that occur after chronic administration of fluoxetine and may be related to the antidepressant effect of the drug. © 1993 Wiley-Liss, Inc.     

Combined treatment with citalopram and buspirone: effects on serotonin 5-HT2A and 5-HT2C receptors in the rat brain

INTRODUCTION: We wanted to elucidate whether the proposed advantages of citalopram-buspirone combination treatment are related to changes in 5-HT(2A/C) receptor-mediated neurotransmission. METHODS: The affinity of buspirone to 5-HT2A and 5-HT2C receptors was measured in vitro, and the influence of buspirone on 5-HT2C receptor-mediated phosphoinositide hydrolysis was estimated. Four groups of rats received citalopram (10 mg/kg), buspirone (6 mg/kg), citalopram-buspirone combination, or saline once a day s.c. for 14 days. Treatment effects on 5-HT2A and 5-HT2C receptors were investigated by receptor autoradiography with antagonist and agonist radioligands. RESULTS: Buspirone was found to be a weak 5-HT2C receptor antagonist, with a low affinity for 5-HT2A and 5-HT2C receptors. Repeated buspirone-citalopram combination treatment markedly decreased [3H]ketanserin and [125I]DOI binding to 5-HT2A receptors. Repeated administration of buspirone and buspirone-citalopram combination increased the affinity of [3H]mesulergine toward 5-HT2C receptors, and buspirone-citalopram combination also decreased [125I]DOI binding to 5-HT2C receptors. DISCUSSION: We suggest that downregulation of brain 5-HT2A receptors and possibly of 5-HT2C receptor agonist sites is involved in the beneficial clinical effects of buspirone-SSRI augmentation treatment. Furthermore, a conversion of brain 5-HT2C receptors from high- to low-affinity state may provide an additional mechanism for the anti-anxiety effects of buspirone.     

Modulation of 5-HT1A receptor mediated response by fluoxetine in rat brain

Summary. Radioligand binding studies were done to investigate the effect of chronic administration of fluoxetine on 5-HT₁ receptor mediated response to adenylate cyclase (AC) in rat brain. Our studies revealed a significant decrease in the densities of 5-HT₁ and 5-HT_1A receptor sites in cortex and hippocampus of rat brain after chronic administration of fluoxetine (10 mg/Kg body wt.). However there was no significant change in the affinity of [³H]5-HT and [³H]DPAT for 5-HT₁ and 5-HT_1A receptor sites, respectively. However, in striatum, along with a significant (75%) downregulation of 5-HT₁ sites, the affinity of [³H]5-HT to these sites was increased, as revealed by decrease in Kd (0.50 ± 0.08 nM). Displacement studies showed that fluoxetine has higher affinity for 5-HT_1A receptors with a Ki value of 14.0 ± 2.8 nM, than 5-HT₁ sites. No significant change was observed in basal AC activity in any region after fluoxetine exposure. However, in cortex of experimental rats the 5-HT stimulated AC activity was significantly increased (16.03 ± 0.97 pmoles/mg protein; p < 0.01), when compared to 5-HT stimulated AC activity (12.98 ± 0.78 pmoles/mg protein) in control rats. The increase in 5-HT stimulated AC activity in cortex may be due to the significant downregulation of 5-HT_1A sites in cortex after fluoxetine exposure as these sites are negatively coupled to AC. The observed significant decrease in 5-HT₁ sites with concomitant increase in 5-HT stimulated AC activity, after fluoxetine treatment, suggests that fluoxetine, which has high affinity for these sites, acts by modulating the 5-HT_1A receptor mediated response in brain. Accepted August 25, 1999     

Stimulation of 5-HT1A, 5-HT1B, 5-HT2A/2C, 5-HT3 and 5-HT4 receptors or 5-HT uptake inhibition: short- and long-term memory

In order to determine whether short- (STM) and long-term memory (LTM) function in serial or parallel manner, serotonin (5-hydroxtryptamine, 5-HT) receptor agonists were tested in autoshaping task. Results show that control-vehicle animals were modestly but significantly mastering the autoshaping task as illustrated by memory scores between STM and LTM. Thus, post-training administration of 8-OHDPAT (agonist for 5-HT(1A/7) receptors) only at 0.250 and 0.500 mg/kg impaired both STM and LTM. CGS12066 (agonist for 5-HT(1B)) produced biphasic affects, at 5.0 mg/kg impaired STM but at 1.0 and 10.0 mg/kg, respectively, improved or impaired LTM. DOI (agonist for 5-HT(2A/2C) receptors) dose-dependently impaired STM and, at 10.0 mg/kg only impaired LTM. Both, STM and LTM were impaired by either mCPP (mainly agonist for 5-HT(2C) receptors) or mesulergine (mainly antagonist for 5-HT(2C) receptors) lower dose. The 5-HT(3) agonist mCPBG at 1.0 impaired STM and its higher dose impaired both STM and LTM. RS67333 (partial agonist for 5-HT(4) receptors), at 5.0 and 10.0 mg/kg facilitated both STM and LTM. The higher dose of fluoxetine (a 5-HT uptake inhibitor) improved both STM and LTM. Using as head-pokes during CS as an indirect measure of food-intake showed that of 30 memory changes, 21 of these were unrelated to the former. While some STM or LTM impairments can be attributed to decrements in food-intake, but not memory changes (either increase or decreases) produced by 8-OHDPAT, CGS12066, RS67333 or fluoxetine. Except for animals treated with DOI, mCPBG or fluoxetine, other groups treated with 5-HT agonists 6 h following autoshaping training showed similar LTM and unmodified CS-head-pokes scores.     

Chronic 5-HT2 receptor antagonist treatment alters 5-HT1A autoregulatory control of 5-HT release in rat brain in vivo.

Rats treated chronically (14 days) with the 5-HT2 receptor antagonist ritanserin, show decreased 5-HT2 receptor numbers in the frontal cortex. The present experiments were designed to investigate the effects of acute and chronic ritanserin treatment on the autoregulatory control of the release of 5-HT and its metabolite 5-HIAA in vivo in rats using intracerebral dialysis. Neither acute nor chronic ritanserin treatment altered basal extracellular levels of 5-HT or 5-HIAA, suggesting that 5-HT2 receptors do not directly influence 5-HT release. In the control animals, systemic stimulation of somatodendritic 5-HT1A receptors with the 5-HT1A receptor agonist 8-OH-DPAT, inhibited the release of 5-HT presumably via inhibitory feedback autoregulation; an effect also seen in animals treated acutely with ritanserin. However, in the animals treated chronically with ritanserin, administration of 8-OH-DPAT produced an initial increase in extracellular 5-HT which declined gradually to the end of the experiment. These results suggest that chronic, but not acute, 5-HT2 receptor antagonist treatment attenuates the 5-HT1A receptor-mediated autoregulation of 5-HT release. The underlying mechanisms have yet to be ascertained.     

Serotonin and learned helplessness: a regional study of 5-HT1A, 5-HT2A receptors and the serotonin transport site in rat brain

Serotonin (5-HT) plays a central role in the neurochemistry of the learned helplessness animal model of depression. Using quantitative autoradiography, we measured the density of 5-HT1A and 5-HT2A receptors and of 5-HT transport sites in medial prefrontal cortex, dorsal hippocampus, septum, hypothalamus, and amygdala in learned helpless rats, and in rats that were nonhelpless after inescapable stress, as well as in shuttlebox-tested and nonhandled controls. We found no changes in 5-HT1A receptor density among the groups in any region studied. In dorsal hippocampus, 5-HT2A receptor density was decreased in nonhelpless rats, while in amygdala 5-HT2A receptor density was decreased in both groups of stressed rats, whether helpless or nonhelpless. In the hypothalamus 5-HT2A receptor density, was decreased in helpless rats as compared to controls. In medial prefrontal cortex, the serotonin transport sites showed decreased density in helpless rats as compared to controls but not to nonhelpless rats. These findings further highlight the complexity of regional 5-HT effects in the learned helplessness animal model.     

Electrophysiological evidence for excitatory 5-HT2 and depressant 5-HT1A receptors on neurones of the rat midbrain tectum.

It has been claimed that the aversive behaviour induced by electrical stimulation of the midbrain tectum (MT) has validity as an animal model of panic attack. A great deal of evidence obtained from behavioural studies suggests that 5-HT2 mechanisms phasically inhibit the substrates of aversion in the MT. In order to test this hypothesis we employed the technique of microiontophoresis of drugs onto neurons of the MT to assess the identity of the receptors mediating the effects of 5-hydroxytryptamine (5-HT). The results obtained show that the majority of 5-HT responsive cells in MT are cells excited by 5-HT (72%). These cells were silent or showed very low spontaneous firing activity, whereas cells depressed by 5-HT showed high spontaneous firing activity at baseline. The 5-HT1A receptor agonists, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), buspirone and gepirone caused consistent reduction in the firing rate of cells depressed by 5-HT while they did not change the firing activity of cells excited by 5-HT. The excitatory effects induced by 5-HT on MT neurones were clearly attenuated by concomitant application of ketanserin, a highly specific 5-HT2 antagonist. Excitatory responses to DL-homocysteic acid were not affected by ketanserin. Previous administration of zimelidine, a selective 5-HT uptake inhibitor, caused a significant enhancement of the excitatory effects of 5-HT while similar application of gepirone did not affect the size of the excitatory responses to 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ex vivo inhibitory effect of the 5-HT uptake blocker citalopram on 5-HT synthesis

Summary Serotonin (5-hydroxytryptamine, 5-HT) synthesis was determined in vivo by measuring the accumulation of 5-hydroxytryptophan (5-HTP) in rat frontal cortex after inhibition of aromatic amino acid decarboxylase by administration of m-hydroxybenzylhydrazine (NSD 1015) (100 mg/kg, i.p.). The selective 5-HT reuptake inhibitor, citalopram, the 5-HT_1a agonists, (±)8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), ipsapirone, gepirone and the 5-HT_1a/b agonist, 7-trifluoromethyl-4(4-methyl-1-piperazinylpyrolo[1,2-a]-quinoxaline (CGS 12066B), the 5-HT_1a/b ligands and -adrenoceptor antagonists, (±)pindolol and (±)alprenolol, and the non-selective 5-HT ligands, m-chlorophenylpiperazine (mCPP) and metergoline, all inhibited the synthesis of 5-HT. The 5-HT_1a /5-HT₂ antagonist, spiperone, alone, had no effect on basal 5-HT synthesis, however it attenuated the effect of 8-OH-DPAT by 56% and CGS 12066B by 39% but only barely that of citalopram by 17%. The selective 5-HT_1a antagonist, WAY 100635, which did not modify by itself 5-HT synthesis, had no effect on citalopram-induced reduction of 5-HT synthesis. Neither the 5-HT₂ agonist, (±)1-(2,5-dimethoxy-4-indophenyl)-2-aminopropane (DOI) nor the 5-HT₂ antagonist, ritanserin, had any effect on the synthesis of 5-HT. In addition, ritanserin did not modify the inhibitory effect of citalopram. Methiothepin was the only compound to increase 5-HT synthesis. These results suggest that the effect of citalopram on the synthesis of 5-HT is not mediated by 5-HT_1a or 5-HT₂ receptors and that other receptors may be involved.     

Somatodendritic localization of 5-HT1A and preterminal axonal localization of 5-HT1B serotonin receptors in adult rat brain

The 5-HT1A and 5-HT1B receptors of serotonin play important roles as auto- and heteroreceptors controlling the release of serotonin itself and of other neurotransmitters/modulators in the central nervous system (CNS). To determine the precise localization of these receptors, we examined their respective cellular and subcellular distributions in the nucleus raphe dorsalis and hippocampal formation (5-HT1A) and in the globus pallidus and substantia nigra (5-HT1B), using light and electron microscopic immunocytochemistry with specific antibodies. Both immunogold and immunoperoxidase preembedding labelings were achieved. In the nucleus raphe dorsalis, 5-HT1A immunoreactivity was found exclusively on neuronal cell bodies and dendrites, and mostly along extrasynaptic portions of their plasma membrane. After immunogold labeling, the density of membrane-associated 5-HT1A receptors could be estimated to be at least 30-40 times that in the cytoplasm. In the hippocampal formation, the somata as well as dendrites of pyramidal and granule cells displayed 5-HT1A immunoreactivity, which was also prominent on the dendritic spines of pyramidal cells. In both substantia nigra and globus pallidus, 5-HT1B receptors were preferentially associated with the membrane of fine, unmyelinated, preterminal axons, and were not found on axon terminals. A selective localization to the cytoplasm of endothelial cells of microvessels was also observed. Because the 5-HT1A receptors are somatodendritic, they are ideally situated to mediate serotonin effects on neuronal firing, both as auto- and as heteroreceptors. The localization of 5-HT1B receptors to the membrane of preterminal axons suggests that they control transmitter release from nonserotonin as well as serotonin neurons by mediating serotonin effects on axonal conduction. The fact that these two receptor subtypes predominate at extrasynaptic and nonsynaptic sites provides further evidence for diffuse serotonin transmission in the CNS.     

Postsynaptic 5-HT1A receptors control 5-HT release in the rat medial prefrontal cortex.

5-HTt1A receptor agonists reduce the neuronal release of 5-hydroxytryptamine (5-HT) by activation of raphe 5-HT1A autoreceptors. Using in vivo microdialysis in unanesthetized rats, we show that the local application of the selective 5-HT1A receptor agonist 8-OH-DPAT decreased the 5-HT output to approximately 50% of controls in medial prefrontal cortex (mPFC) but not in dorsal hippocampus. The decrease in 5-HT output was counteracted by the concurrent application of the selective 5-HT1A receptor antagonist WAY-100635. This agent also reversed the decrease in 5-HT output elicited by the novel 5-HT1A receptor agonist BAY x 3702 (30 microM) in mPFC and dorsal raphe nucleus. These results indicate that postsynaptic 5-HT1A receptors in mPFC also participate in the control of serotonergic activity.     

Effects of repeated injections of cocaine on D1 and D2 dopamine receptors in rat brain

In order to determine if chronic administration of cocaine produced long-lasting alterations in dopamine receptor binding, rats were treated with single daily injections of cocaine (0, 10, or 20 mg/kg) for 15 consecutive days and killed either 20 min or 2 weeks after the last injection. The density of D1 binding sites in frontal cortex was either unchanged (10 mg/kg) or slightly increased (20 mg/kg) 20 min after the last daily injection, but was decreased 2 weeks later. D1 sites in striatum were decreased both immediately and 2 weeks after the injection regimen. Decreases in D1 binding site density in nucleus accumbens were observed only immediately after the last injection. In contrast to these effects on D1 binding sites, D2 binding sites were decreased in striatum and frontal cortex and increased in the nucleus accumbens 20 min after repeated cocaine, but were unaffected 2 weeks after repeated cocaine. Computer-assisted analysis of the saturation isotherms revealed that chronic administration of cocaine did not affect the affinity (Kd) of the radioligands used to label D1 or D2 sites. These findings suggest that repeated administration of cocaine results in long-term decreases in D1 binding sites in striatum and frontal cortex and transient decreases in D2 binding sites. Furthermore, cocaine caused opposite, transient effects on D1 and D2 site density in nucleus accumbens.     

In vivo occupation of dopamine D1, D2 and serotonin (5-HT)2A receptors by sertindole in the rat brain.

OBJECTIVE: To determine the in vivo occupation of dopamine D1, D2 and serotonin (5-HT)2A receptors by novel antipsychotic agent sertindole using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), an irreversible antagonist at these receptor sites. DESIGN: Animal study. INTERVENTIONS: Intraperitoneal administration to Wistar rats of 1 of 4 test compounds: a control compound of 0.15% tartaric acid, or a compound of either sertindole (0.5 mg/kg or 2.0 mg/kg) or clozapine (20 mg/kg) dissolved in 0.15% tartaric acid 1 hour before intraperitoneal administration of EEDQ (8 mg/kg) or ethanol/water solution. RESULTS: Sertindole exhibited little or no effect on D1 and D2 binding sites in vivo. On the other hand, sertindole occupied 5-HT2A receptors more extensively and firmly than EEDQ. This study indicates that sertindole is characterized by high occupancy of 5-HT2A receptors and by low or minimum occupancy of D1 and D2 receptors. CONCLUSIONS: These characteristics are very similar to atypical antipsychotic agents such as clozapine. Sertindole's low liability to cause extrapyramidal side effects (EPS) may be related to greater long-term binding for 5-HT2A receptors relative to D2 receptors.     

Short-term lithium treatment enhances responsiveness of postsynaptic 5-HT1A receptors without altering 5-HT autoreceptor sensitivity: an electrophysiological study in the rat brain

Short-term lithium administration to rats has previously been shown to enhance 5-HT neurotransmission through a modification of 5-HT neuron properties. In the first part of the present study, the effect of lithium on the function of terminal 5-HT autoreceptors was assessed by comparing in controls and lithium-treated rats the differential effect of two frequencies of stimulation (0.8 and 5 Hz) and that of methiothepin, a terminal 5-HT autoreceptor antagonist, on the effectiveness of the electrical activation of the ascending 5-HT pathway in suppressing dorsal hippocampus pyramidal neuron firing activity. Both procedures produced similar effects in controls and lithium-treated rats. In the second part of the study, the function of somatodendritic 5-HT autoreceptors was studied. The effect of intravenous LSD, an agonist of the somatodendritic 5-HT autoreceptor, on the firing activity of 5-HT neurons was not modified by the lithium treatment, whereas that of intravenous 8-OH-DPAT, a 5-HT1A receptor agonist, was increased two-fold. However, lithium did not alter the responsiveness of 5-HT neurons to direct microiontophoretic applications of 8-OH-DPAT as well as of LSD and 5-HT. It is concluded that short-term lithium treatment does not alter the function of terminal and somatodendritic 5-HT autoreceptors and that it enhances the sensitivity of a subset of postsynaptic 5-HT1A receptors involved in controlling 5-HT neuron firing activity, presumably through a feedback loop.     

The therapeutic role of 5-HT1A and 5-HT2A receptors in depression

The selective serotonin reuptake inhibitors (SSRIs) are the most frequently prescribed antidepressant drugs, because they are well tolerated and have no severe side effects. They rapidly block serotonin (5-HT) reuptake, yet the onset of their therapeutic action requires weeks of treatment. This delay is the result of presynaptic and postsynaptic adaptive mechanisms secondary to reuptake inhibition. The prevention of a negative feedback mechanism operating at the 5-HT autoreceptor level enhances the neurochemical and clinical effects of SSRIs. The blockade of 5-HT2A receptors also seems to improve the clinical effects of SSRIs. These receptors are located postsynaptically to 5-HT axons, mainly in the neocortex. Pyramidal neurons in the prefrontal cortex are particularly enriched in 5-HT2A receptors. Their blockade may affect the function of prefrontal-subcortical circuits, an effect that probably underlies the beneficial effects of the addition of atypical antipsychotic drugs, which are 5-HT2A receptor antagonists, to SSRIs in treatment-resistant patients.     

Serotonin receptors in the human brain. II. Characterization and autoradiographic localization of 5-HT1C and 5-HT2 recognition sites

The presence, pharmacological properties and anatomical distribution of serotonin-1C and serotonin-2 receptor subtypes were studied in the human brain by both radioligand binding and autoradiographic procedures. Frontal cortex, hippocampus and choroid plexus from human brains obtained at autopsy without history of neurological diseases were used in this study. [3H]5-HT and [3H]mesulergine were used to label 5-HT1C recognition sites while [3H]ketanserin was used to label 5-HT2 receptors. The pharmacological profile of 5-HT1C sites which are very concentrated in the choroid plexus, was extremely similar to that of pig and rat 5-HT1C sites. These receptors were also detected in the hippocampus and the cortex from human brain. The general distribution of 5-HT1C sites in human and rat brain was similar although slight differences were observed. Human 5-HT2 receptors were concentrated in cortical areas but also found in the hippocampus. The pharmacological profile of these receptors was extremely similar in human and pig brain tissue, but differed in certain respects to that found in rat brain 5-HT2 receptors. The anatomical distribution of 5-HT2 receptors is similar in human and rat brain with some differences at the microscopic level. The importance of species differences in the development of 5-HT2 compounds is discussed.     

Postsynaptic localization and up-regulation of serotonin 5-HT1D receptors in rat brain

Serotonin lesioning studies were performed to determine the synaptic localization of the 5-HT1D receptor. Four days following p-chloroamphetamine (PCA; 5 mg/kg x 4) [3H]paroxetine-labeled uptake sites (a marker for 5-HT terminals) were reduced to 18% of control values in the cortex and 29% of control values in the striatum, while the number of 5-HT1D receptors remained unchanged. Fourteen days following PCA administration an up-regulation of cortical 5-HT1D receptors was observed. These findings indicate that 5-HT1D receptors are localized postsynaptically in the cortex and striatum, and that denervation of endogenous serotonergic input produces a compensatory up-regulation in the cortex.     

Effects of dorsal rhizotomy and selective lesion of serotonergic and noradrenergic systems on 5-HT1a , 5-HT1b and 5-HT3 receptors in the rat spinal cord

Summary Autoradiographic studies were performed in combination with dorsal rhizotomy or selective lesion of descending serotonergic or noradrenergic systems in an attempt to identify the neuronal cell types endowed with the serotonin 5-HT_1a , 5-HT_1b and 5-HT₃ receptors in the rat spinal cord. Unilateral sectioning of seven dorsal roots (C4–T2) at the cervical level produced a marked decrease (–75%, 10 days after the surgery) in the binding of [¹²⁵I]iodozacopride to 5-HT₃ receptors in the superficial layers of the ipsilateral dorsal horn, further confirming the preferential location of these receptors on primary afferent fibres. In addition, a significant decrease (20%) in the binding of [³H]8-OH-DPAT to 5-HT_1A receptors and of [¹²⁵I]GTI to 5-HT_1B receptors was also observed in the same spinal area in rhizotomized rats, suggesting that a small proportion of these receptors are also located on primary afferent fibres. The labelling of 5-HT_1B receptors was significantly decreased (–12%) in the dorsal horn at the cervical (but not the lumbar) level, and that of 5-HT₃ receptors was unchanged in the whole spinal cord in rats whose descending serotonergic projections had been destroyed by 5,7-dihydroxytryptamine. Conversely, the labelling of 5-HT_1A receptors was significantly increased in the cervical (+13%) and lumbar (+42%) dorsal horn in 5,7-dihydroxytryptamine-lesioned rats. Similarly, [³H]8-OH-DPAT binding to 5-HT_1A receptors significantly increased (+26%) in the lumbar (but not the cervical) dorsal horn in rats whose noradrenergic systems had been lesioned by DSP-4. The labelling of 5-HT_1B receptors was also increased (+31% at the cervical level; +17% at the lumbar level), whereas that of 5-HT₃ receptors remained unchanged in these animals. These data indicate that complex adaptive changes in the expression of 5-HT_1A and 5-HT_1B receptors occurred in the rat spinal cord following the lesion of descending monoaminergic systems.Abbreviations CP 93129 3-(1,2,5,6-tetrahydropyrid-4-yl) pyrrolo [3,2-b]pyrid-5-one - 5,7-DHT 5,7-dihydroxytryptamine - DSP-4 N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine - GTI serotonin-O-carboxymethylglycyl-iodotyrosinamide - HEPES 4-(2-hydroxyethyl)-l-piperazine ethane sulfonic acid - 5-HT 5-hydroxytryptamine - i.c. intracisternally - NA noradrenaline - 8-OH-DPAT 8-hydroxy-2-(di-n-propylamino)tetralin     

西酞普兰与氟西汀治疗抑郁症对照研究

目的：验证西酞普兰治疗抑郁症的疗效及安全性。方法：按前瞻性，随机、单盲法将56例抑郁症患者分为西酞普兰组与氟西汀组。疗程6周。在疗前、治疗1、2、6周用汉密尔顿抑郁量表(HAMD)、汉密尔顿焦虑量表(HAMA)评定疗效，用副反应量表(TESS)、实验室检查及体检评价安全性。结果：两组总体疗效相当。但2周末时HAMD评分及减分率、HAMA评分两组问差异有显著性，说明西酞普兰起效较快。两组不良反应均较轻，安全性好。结论：西酞普兰是一种安全有效的抗抑郁药，耐受性及依从性好。     

5-HT2C receptors inhibit and 5-HT1A receptors activate the generation of spike-wave discharges in a genetic rat model of absence epilepsy

The present study was conducted to investigate the role of 5-HT(2C) and 5-HT(1A) receptors in the generation of spike-wave discharges (SWD) in the genetic absence epilepsy model Wistar Albino Glaxo rats from Rijswijk, Netherlands (WAG/Rij rats). We have determined the effects of the 5-HT(2C) receptor preferring agonist m-chlorophenyl-piperazine (m-CPP), the selective 5-HT(2C) receptor antagonist SB-242084, the selective 5-HT(1A) receptor antagonist WAY-100635, two selective serotonin re-uptake inhibitors (SSRI, fluoxetine and citalopram) and their combinations in this model. The 5-HT(2C) agonist m-CPP caused marked, dose-dependent decreases in the cumulative duration and number of SWD administered either intraperitoneally (0.9 and 2.5 mg/kg) or intracerebroventricularly (0.05 and 0.1 mg/kg). Treatment with SB-242084 (0.2 mg/kg, ip) alone failed to cause any significant change in SWD compared to vehicle. Pretreatment with SB-242084 (0.2 mg/kg, ip) eliminated the effects of m-CPP on SWD. Fluoxetine (5.0 mg/kg, ip) alone caused moderate increase in SWD. After pretreatment with SB-242084, the effect of fluoxetine was significantly enhanced. The combination of SB-242084 and citalopram (2.5 mg/kg, ip) caused a similar effect, namely an increase in SWD. In contrast, pretreatment with WAY-100635 significantly attenuated the effect of fluoxetine. In conclusion, these results indicate that the increase in endogenous 5-HT produces a dual effect on SWD; the inhibition of epileptiform activity is mediated by 5-HT(2C), the activation by 5-HT(1A) receptors.     

Changes in exploratory activity following stimulation of hippocampal 5-HT1A and 5-HT1B receptors in the rat

The object exploration task allows the measure of changes in locomotor and exploratory activities, habituation, and reaction to a spatial change and to novelty. The effects of intrahippocampal (dorsal CA1 field) microinjections of serotonin 1 receptor (5-HT1) agonists on these behavioral components were evaluated in the rat. 8-Hydroxy-2-(din-propylamino)-tetralin (8-OH-DPAT,5 μg/μl) was used as a 5-HT1A agonist, 3-(1,2,5,6-tetrahydropyrid-4-yl) pyrrolo[3,2-b] pyrid-5-one (CP 93,129, 16 μg/μl) as a 5-HT1B agonist, and scopolamine (10 μg/μl) as a muscarinic cholinergic antagonist. Scopolamine induced a long-lasting increase in locomotor activity and a lack of reaction to spatial change; both these results are in agreement with the known crucial influence of the septo-hippocampal cholinergic system in hippocampal functioning. Stimulation of 5-HT1A and 5-HT1B receptors induced a decrease in object exploration and habituation without affecting the retrieval of spatial information. But stimulation of hippocampal 5-HT1B receptors induced a selective change in the animal's emotional state, i.e., an initial decrease in locomotor activity and a neophobic reaction in response to a new object; such effects did not occur following stimulation of 5HT1A receptors. These results have to be considered in the light of the anxiogenic propety of 5-HT1B agonists. On the whole, they support the hypothesis of the involvement of the serotonergic system, via 5HT1A and 5-HT1B receptors, in the modulation of hippocampal functions. © 1995 Wiley-Liss, Inc.