Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P08908 (5-HT1A)
 5,574 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical properties of the 5-HT1A receptor in dorsal raphe nucleus (DRN) were investigated using a micropunch procedure. Initially, the Ki value for 5-hydroxytryptamine (5-HT) binding to a site labeled by the 5-HT1A-selective ligand [3H]8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was 20-fold higher than the KD for [3H]5-HT. In addition, a number of putative 5-HT1A selective ligands displayed poor affinity for the [3H]8-OH-DPAT site. The possibility that these discrepant results were due to metabolism of the receptor ligands was investigated by increasing the concentration of the monoamine oxidase (MAO) inhibitor, pargyline. Increasing the concentration of pargyline reduced, but did not abolish, the discrepancy between the Ki and KD values for 5-HT. However, inclusion of clorgyline, which is a more potent MAO inhibitor, resulted in an-excellent agreement between the Ki and KD values for 5-HT. In addition, when clorgyline was used, 5-HT1A-selective compounds displayed high affinity for the DRN binding site consistent with [3H]8-OH-DPAT labeling a 5-HT1A receptor in this tissue. The present study describes a fast and easy method for measuring biochemical properties in small discrete brain areas. These studies also indicate that pargyline should be replaced in serotonergic binding assays with a more potent inhibitor of monoamine oxidase such as clorgyline.
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PMID:Serotonergic binding in the rat dorsal raphe nucleus: critical role of MAO inhibition. 891 26

The serotonin (5-HT)-increasing action of 5-HT uptake or monoamine oxidase inhibitors is limited by a negative feedback at somatodendritic level. The excess 5-HT produced by these antidepressant drugs in the interstitial space of the midbrain raphe activates somatodendritic 5-HT1A autoreceptors, thereby attenuating terminal 5-HT release. This effect is maximal in forebrain areas innervated by the dorsal raphe nucleus and can be prevented by the administration of non-selective [(-)pindolol, (-)tertatolol] and selective (WAY-100635) 5-HT1A antagonists. In keeping with these observations, the combined administration of selective serotonin reuptake inhibitors (SSRIs) and 5-HT1A antagonists increase the cortical and striatal extracellular 5-HT concentration more than the former alone. Also, concurrent inhibition of the 5-HT and noradrenaline transporters with 20 mg/kg imipramine increases cortical extracellular 5-HT concentration more than SSRI doses which maximally block the 5-HT transporter. Moreover, the effects of fluoxetine on frontal cortex 5-HT are potentiated by a dose of desipramine that does not modify extracellular 5-HT by itself. Given the relevance of increased serotonergic transmission in the treatment of depression, these experimental data indicate that dual-action antidepressant treatments may be more effective than those which selectively inhibit the 5-HT transporter.
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PMID:Two actions are better than one: avoiding self-inhibition of serotonergic neurones enhances the effects of serotonin uptake inhibitors. 892 21

Guinea pigs possess central 5-HT1D receptors similar to humans but different from rats and mice. In order to study the role of this receptor on animal behaviour, it may be of interest to develop a paradigm measuring affective states in the guinea pig. Therefore we assessed the effects of a variety of psychotropic drugs on guinea pig pup isolation calls. Anxiolytic compounds such as the benzodiazepine receptor agonists diazepam and alprazolam, the full 5-HT1A receptor agonists 8-OH-DPAT and flesinoxan, and alcohol reduced isolation calling by the guinea pig pup. Moreover, mixed antidepressant/anxiolytic compounds like the 5-HT uptake inhibitors fluvoxamine and clomipramine or the MAO-inhibitor clorgyline as well as the antidepressant NA uptake inhibitors desipramine and maprotiline suppressed vocalizations. The 5-HT1D/1A receptor agonist 5-CT was also very effective in reducing separation calls. Remarkably, the partial 5-HT1A receptor agonists buspirone and BMY 7378 did not affect calling. The neuroleptic haloperidol, the psychostimulant d-amphetamine, the putative anxiogenics DMCM and m-CPP and the putative anxiolytics ondansetron and CI-988 had no effect on isolation calls of guinea pig pups. We propose this paradigm could be helpful to assess behavioural effects of anxiolytic and antidepressant drugs in a species different from rat or mouse, and in which the effects of 5-HT1D receptor ligands may possibly be established.
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PMID:Reduction of guinea pig pup isolation calls by anxiolytic and antidepressant drugs. 894 3

The increases in extracellular serotonin (5-hydroxytryptamine; 5-HT) produced by some antidepressent drugs in forebrain are attenuated by the activation of somatodendritic 5-HT1A autoreceptors by the excess 5-HT induced by these agents in the midbrain raphe. Using microdialysis, we have examined the effects of the selective 5-HT1A antagonist WAY-100635 in rats pretreated with the selective 5-HT reuptake inhibitors (SSRIs) citalopram, fluoxetine, fluvoxamine, the tricyclic antidepressants clomipramine and desipramine and the monoamine oxidase inhibitor phenelzine. WAY-100635 markedly potentiated the increases in 5-HT produced by the SSRIs, clomipramine and phenelzine but it did not alter that produced by desipramine. These results indicate that the effects of serotonergic antidepressant drugs (but not those of desipramine, which mainly blocks noradrenaline reuptake) can be potentiated by 5-HT1A autoreceptor blockade.
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PMID:The 5-HT1A antagonist WAY-100635 selectively potentiates the presynaptic effects of serotonergic antidepressants in rat brain. 897 95

Fast cyclic voltammetry (FCV) was used to measure electrically stimulated monoamine efflux in the rat ventral lateral geniculate nucleus (vLGN). The electrochemical characteristics of the released species resembled 5-HT but not dopamine or noradrenaline. Amine efflux was abolished by the sodium channel blocker tetrodotoxin (0.1 microM), Ro 4-1284 (1.0 microM), the fast-acting reserpine analogue, and removal of Ca2+ from the superfusate. Amine efflux was unaffected by the monoamine oxidase inhibitor clorgyline (0.1 microM). Of paroxetine (0.1 microM), desipramine (50 nM) and vanoxerine (0.5 microM), selective blockers of 5-HT, noradrenaline and dopamine uptake respectively, only paroxetine increased monoamine efflux (to 194 +/- 25%, mean +/- SEM) and prolonged the removal half-life (to 638 +/- 105%). The non-specific 5-HT1 antagonist methiothepin (0.2 microM) increased 5-HT efflux on long (20 pulses at 20 Hz) but not short trains (20 pulses at 100 Hz). When tested on pseudo-one-pulse stimulations (5 pulses, 100 Hz), the selective 5-HT1A agonist 8-OHDPAT (1.0 microM) had no effect. CP 93129 (0.3 microM), the selective 5-HT1B agonist, decreased 5-HT efflux to 37 +/- 4% of control and was antagonised by the 5-HT1B blocker isamoltane (0.5 microM) and by the 5-HT1D/B antagonist GR 127935 (50 nM). The preferential 5-HT1D agonist sumatriptan (0.5 microM) also decreased 5-HT efflux, to 55 +/- 6% and was antagonised by GR 127935 (50 nM) but not isamoltane (0.5 microM). These results suggest that 5-HT released in the vLGN can be measured by FCV. Furthermore, released 5-HT is taken up by the 5-HT transporter and may be under the influence of 5-HT1B and 5-HT1D autoreceptors.
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PMID:Serotonin efflux in the rat ventral lateral geniculate nucleus assessed by fast cyclic voltammetry is modulated by 5-HT1B and 5-HT1D autoreceptors. 902 11

We report the effects of the monoamine oxidase inhibitor, tranylcypromine, combined with the 5-HT1A receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl cyclohexanecarboxamide (WAY 100635), on both 5-hydroxytryptamine (5-HT) cell firing and cortical extracellular 5-HT in the rat. Tranylcypromine inhibited 5-HT cell firing in the dorsal raphe nucleus dose-dependently (ED50 5 mg/kg i.v.). In microdialysis experiments, tranylcypromine (5 mg/kg i.v.) increased extracellular 5-HT in the frontal cortex. WAY 100635 (0.1 mg/kg i.v.) both reversed the inhibition of 5-HT cell firing and facilitated the increase in extracellular 5-HT. In conclusion, WAY 100635 enhances the effect of tranylcypromine on presynaptic 5-HT function. These data are relevant to clinical evidence that co-therapy with a 5-HT1A receptor antagonist improves the antidepressant efficacy of a monoamine oxidase inhibitor.
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PMID:Effects of co-administration of a monoamine oxidase inhibitor and a 5-HT1A receptor antagonist on 5-hydroxytryptamine cell firing and release. 904 97

The objectives of this study were to characterize the effects of a chronic lithium (Li+) treatment on serotonin (5-HT) uptake sites and on 5-HT1A receptors, and to determine the eventual reversibility of the treatment. The experiments were carried out with membranes from rat cerebral cortex using 8-hydroxy-2-(propylamino)tetralin, or [3H]8-OH-DPAT, and [3H]citalopram to label 5-HT1A receptors and 5-HT uptake sites, respectively. Endogenous levels of 5-HT and 5-hydroxyindole-3-acetic acid (5-HIAA) were measured by high-performance liquid chromatography in the cingulate cortex. The saturation curves with [3H]8-OH-DPAT were always best fitted a two-site model. After a treatment with Li+ for 28 days, no alterations in the binding parameters of [3H]8-OH-DPAT to the high- and low-affinity binding sites could be documented. However, competition curves with 5-HT to inhibit [3H]8-OH-DPAT binding revealed a decreased proportion of sites with high affinity for the agonist, together with an increased density of sites with low affinity for 5-HT, suggesting an alteration in the coupling efficacy between 5-HT1A receptors and their transduction systems. Saturation studies with [3H]citalopram showed an increase (> 40%) in the density of 5-HT uptake sites after chronic Li+, suggesting a more efficient 5-HT uptake process for the treated animals, in accord with clinical observations. Although 5-HT contents in cingulate cortex remained unchanged after the treatment, 5-H[AA levels decreased (> 30%), leading to a diminished (almost 50%) 5-HT turnover; and also reflecting a more efficient uptake in the treated rats, so that less 5-HT could be degraded by extracellular monoamine oxidase. All the effects revealed by [3H]8-OH-DPAT and [3H]citalopram were reversed following a recovery period of two days without Li+. Since symptoms of bipolar affective disorders may reappear if the chronic Li+ treatment is interrupted, the reversibility of the observed effects further supports the importance of central 5-HT synaptic transmission in the pathophysiology and treatment of human affective disorders.
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PMID:Effects of a chronic lithium treatment on cortical serotonin uptake sites and 5-HT1A receptors. 913 Feb 53

Social phobia is a common anxiety disorder that is underdiagnosed and undertreated. To date, three classes of serotonin drugs have been used to treat patients suffering from social phobia. These include the serotonin selective reuptake inhibitors (SSRIs), the partial 5-HT1A agonist buspirone, and the 5-HT3 antagonist ondansetron. Although none of the serotonin agents have yet been directly compared with the gold standard monoamine oxidase inhibitor phenelzine or the high potency triazolobenzo-diazepines alprazolam or clonazepam, the SSRIs, as a class, appear to be clinically useful agents. Further studies using larger sample sizes and double-blind methodology are needed to clarify the role of serotonin drugs in the treatment of social phobia.
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PMID:Role of serotonin drugs in the treatment of social phobia. 918 26

In silver foxes significant alterations in the activities of basic enzymes of neurotransmitter serotonin metabolism as well as in the densities of receptors caused by selection for the absence of the aggressive defensive reaction to man were demonstrated. In the midbrain and hypothalamus of animals selected for the absence of aggressive behavior, the activity of tryptophan hydroxylase, the key enzyme of serotonin biosynthesis, was found to be remarkably higher than in animals selected for highly aggressive behavior. Domesticated animals were characterized by low activity of the main enzyme of serotonin catabolism, monoamine oxidase type A, increased Michaelis constant km, and an unchanged maximum reaction rate (Vmax). No changes in the specific binding of [3H]-ketanserin and [3H]-8-OH-DPAT in the frontal cortex of domesticated foxes were revealed; however, in the hypothalamus, the low values of Bmax for the [3H]-8-OH-DPAT specific binding were observed, indicating the decreased density of the 5-HT1A receptors. It is assumed that the transformation of a wild aggressive animal into a domesticated one taking place during directional selection is caused by hereditary alterations favored by artificial selection in the activity of the main enzymes of serotonin metabolism and serotonin receptors.
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PMID:[Effect of domestication of the silver fox on the main enzymes of serotonin metabolism and serotonin receptors]. 924 68

Alterations in the function of the neurotransmitter serotonin (5-HT) have been implicated in several neurobehavioral disorders, including depression, anxiety as well as a well-known disorder of aging, Alzheimer's disease. Age-dependent changes in the serotonergic system include a loss of 5-HT-containing fibers in brain areas which contain high levels of 5-HT1A receptors. Other changes with aging include decreased 5-HT levels, increases in monoamine oxidase (the major 5-HT degrading enzyme), and decreases in the density of 5-HT receptors. While age-related declines in the number of 5-HT1B and 5-HT2 receptors have been reported, little information is available describing the region-specific effects of aging on the functional dynamics of equilibrium binding at 5-HT receptors, including the 5-HT1A receptor subtype. For example, there are limited data showing a decrease in the maximal binding capacity (Bmax) of 5-HT1A receptors in the aging cortex of humans. However, changes in affinity (Kd) for this receptor subtype as a function of age and brain region have not been fully investigated. Other reports have failed to indicate age-related modifications in human and rat brain tissue 5-HT1A binding parameters. In contrast, electrophysiological studies suggest that the physiological function of the 5-HT1A receptor population is altered with aging. Therefore, to elucidate region-specific 5-HT1A receptor binding characteristics in aging rats, we have utilized a neurotoxic agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) to irreversibly inactivate 5-HT1A receptors. In this way, subsequent age-related changes that occur in 5-HT1A receptor binding characteristics may be investigated. EEDQ is an alkylating agent which irreversibly inactivates serotonergic receptors which are coupled to G proteins. This compound is appropriate for examining the binding profile of several 5-HT receptors, including the 5-HT1A receptor. The 5-HT1A binding site is among the most sensitive of the serotonergic receptor subtypes to inactivation by EEDQ and is also negatively coupled to adenylate cyclase via interaction with a Gi protein. Thus, EEDQ administration is a useful neurotoxicant to examine the relationship between aging and binding characteristics of 5-HT1A receptors. In addition, using EEDQ to inactivate 5-HT1A binding sites, we can further investigate the extent to which receptor binding characteristics (Bmax and Kd) return to baseline levels (i.e., recover) in an age- and brain region-dependent manner following a neurotoxic insult. That is, the age- and region-dependent recovery of 5-HT1A receptors may be monitored in a time-dependent manner to determine receptor turnover parameters, including receptor synthesis and degradation rate constants, and half-life values. Following receptor inactivation by EEDQ, 5-HT1A receptors repopulate (i.e., return to baseline levels) with time and exhibit region-specific turnover rates. Therefore, EEDQ administration is an effective pharmacological tool to investigate region-specific differences in 5-HT1A receptor turnover characteristics. Likewise, by utilizing this neurotoxicant the cellular mechanisms by which pharmacological agents interact with central 5-HT receptors and produce their effects in the aging brain can be addressed. We will illustrate the application of the neurotoxicant EEDQ to irreversibly inactivate 5-HT1A receptors. Following EEDQ administration, region-specific changes in 5-HT1A binding characteristics, including receptor density and drug affinity, and kinetics of receptor recovery will be demonstrated by Scatchard analyses and calculations of the recovery of these receptor populations illustrated. Based on the presence of high densities of 5-HT1A receptors in the hippocampus and frontal cortex, these brain regions will be studied for comparisons of both age- and region-specific alterations in receptor binding characteristics.
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PMID:N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) administration for studies of 5-HT1A receptor binding site inactivation and turnover. 938 17


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