Effects of blockade of 5-HT2A receptors in inflammatory site on complete Freund's adjuvant-induced chronic hyperalgesia and neuropeptide Y expression in the spinal dorsal horn in rats / 生理学报

5-hydroxytryptamine (5-HT) released in inflammatory tissues plays a pivotal role in pain hypersensitivity. However, it is not clear whether 5-HT2A receptors in the inflamed tissues mediate this effect. The present study investigated the contribution of 5-HT2A receptors in the periphery to chronic inflammatory pain. Complete Freund's adjuvant (CFA) was injected subcutaneously in the hindpaw of rats. The selective 5-HT2A receptor antagonist ketanserin was given in the inflamed site. Paw withdrawal latency responding to heat or mechanical stimuli was measured. Expression of neuropeptide Y (NPY) in the spinal dorsal horn and dorsal root ganglia (DRG) was assayed using immunohistochemistry technique. The results showed that ketanserin administered in the inflamed site inhibited thermal hyperalgesia in a dose-dependent manner (20, 40 and 80 µg) induced by the intraplantar injection of CFA. Ketanserin given once per day at a dose of 80 µg abolished heat hyperalgesia and also attenuated mechanical allodynia on the third day. CFA injection increased the expression of NPY in superficial laminae of the spinal cord, but not in the DRG. The local treatment of ketanserin completely inhibited CFA-induced increase in NPY expression in superficial laminae of the spinal cord. These results indicated that activation of 5-HT2A receptors in the inflamed tissues was involved in the pathogenesis of inflammatory pain and the blockade of 5-HT2A receptors in the periphery could relieve pain hypersensitivity and normalize the cellular disorder in the spinal dorsal horn associated with pathological pain. The present study suggests that the peripheral 5-HT2A receptors can be a promising target for pharmaceutical therapy to treat chronic inflammatory pain without central nervous system side effects.

Serotonin contracts the rat mesenteric artery by inhibiting 4-aminopyridine-sensitive Kv channels via the 5-HT2A receptor and Src tyrosine kinase

Serotonin (5-hydroxytryptamine (5-HT)) is a neurotransmitter that regulates a variety of functions in the nervous, gastrointestinal and cardiovascular systems. Despite such importance, 5-HT signaling pathways are not entirely clear. We demonstrated previously that 4-aminopyridine (4-AP)-sensitive voltage-gated K+ (Kv) channels determine the resting membrane potential of arterial smooth muscle cells and that the Kv channels are inhibited by 5-HT, which depolarizes the membranes. Therefore, we hypothesized that 5-HT contracts arteries by inhibiting Kv channels. Here we studied 5-HT signaling and the detailed role of Kv currents in rat mesenteric arteries using patch-clamp and isometric tension measurements. Our data showed that inhibiting 4-AP-sensitive Kv channels contracted arterial rings, whereas inhibiting Ca2+-activated K+, inward rectifier K+ and ATP-sensitive K+ channels had little effect on arterial contraction, indicating a central role of Kv channels in the regulation of resting arterial tone. 5-HT-induced arterial contraction decreased significantly in the presence of high KCl or the voltage-gated Ca2+ channel (VGCC) inhibitor nifedipine, indicating that membrane depolarization and the consequent activation of VGCCs mediate the 5-HT-induced vasoconstriction. The effects of 5-HT on Kv currents and arterial contraction were markedly prevented by the 5-HT2A receptor antagonists ketanserin and spiperone. Consistently, alpha-methyl 5-HT, a 5-HT2 receptor agonist, mimicked the 5-HT action on Kv channels. Pretreatment with a Src tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, prevented both the 5-HT-mediated vasoconstriction and Kv current inhibition. Our data suggest that 4-AP-sensitive Kv channels are the primary regulator of the resting tone in rat mesenteric arteries. 5-HT constricts the arteries by inhibiting Kv channels via the 5-HT2A receptor and Src tyrosine kinase pathway.

Comparative pharmacophore analysis of dual dopamine D2/5-HT(2A) receptor antagonists / 药学学报

Dual dopamine D2/5-HT2A receptor antagonists have potent activity and are referred to atypical antipsychotics due to their lower propensity to elicit EPS and their moderate efficacy toward negative symptoms. However, an on-going challenge in developing atypical antipsychotics drugs is to maintain the favorable profiles and avoid of cardiovascular risk. In this paper, comparative pharmacophore analysis of dual dopamine D2/5-HT2A receptor antagonists, hERG K+ channel blockers, and alA adrenoceptor antagonists is carried out, and the results could give some insight into multi-target drug design.

5-HT2 receptor mediated the potentiation of GABA-activated current in the membrane of the dorsal root ganglion neurons of rat / 药学学报

<p><b>AIM</b>To explore the modulation of 5-HT on GABA-activated current (I(GABA)) in the membrane of rat dorsal root ganglion (DRG) neurons and its mechanism.</p><p><b>METHODS</b>Rat DRG neurons were isolated mechanically and enzymatically, on which whole-cell patch clamp recording and repatch technique for intracellular dialysis were performed.</p><p><b>RESULTS</b>In the majority of neurons examined (92.0%, 69/75) GABA induced a concentration-dependent inward current. In neurons sensitive to GABA preapplication of 5-HT produced potentiation effect (82.6% , 57/69) on I(GABA). Preapplication of 5-HT at concentrations of 1 x 10(-6), 1 x 10(-5), 1 x 10(-4) and 1 x 10(-3) mol x L(-1) potentiated I(GABA) by (35 +/- 8)% (n=8), (47 +/- 11)% (n=10), (65 +/- 17)% (n=9) and (75 +/- 18)% (n=11), respectively. This effect was mimicked by alpha-methyl-5-HT (1 x 10(-6) mol x L(-1)), a specific 5-HT2 receptor agonist, and reversed by cyproheptadine, a selective 5-HT2 receptor antagonist. The potentiation of I(GABA) by 5-HT was irrespective to whether the I(5-HT) presents or not in a subset of neurons. The concentration-response curves for GABA before and after pretreatment with 5-HT manifested the same threshold value and similar EC50 (2.0 x 10(-5) and 1.9 x 10(-5) mol x L(-1), respectively) , while the maximal value of I(GABA) for the latter was 33.6% higher than that for the former. Intracellular dialysis with GDP-beta-S or H-7 abolished the potentiation of I(GABA) by 5-HT, while H-9 did not.</p><p><b>CONCLUSION</b>5-HT can potentiate GABA-activated current via PKC-dependent phosphorylation of GABA(A) receptor following the activation of 5-HT2 receptor.</p>

5-HT2C receptor subtype modulate production of secretory beta-amyloid protein precursor in incubated rat hippocampal slices / 药学学报

<p><b>AIM</b>To determine whether serotonin, a major neurotransmitter in brain, can modulate the production of secretory beta-amyloid protein precursor (sAPP) by activation of serotonin 5-HT2C receptor.</p><p><b>METHODS</b>The hippocampal slices of rats were incubated with various concentrations of serotonin, M-110, or L-107. sAPP released into the incubation medium were assayed by Western blot analysis assay with monoclonal antibody 22C11 for 2 h.</p><p><b>RESULTS</b>Various concentrations of serotonin (1.0 x 10(-2) - 1.0 x 10(3) micromol x L(-1)), M-110, a serotonin 5-HT2C agonist (1.5 x 10(-6) - 1.5 x 10(3) micromol x L(-1)), showed positive effect on the production of sAPP while L-107, a serotonin 5-HT2C antagonist (1.0 x 10(-9) - 1.0 x 10(3) micromol x L(-1)), showed negative effect on the production of sAPP over controls.</p><p><b>CONCLUSION</b>Serotonin modulates production of secretory amyloid beta-protein precursor through serotonin 5-HT2C receptor in incubated rat hippocampal slices.</p>

Role of 5-HT2A Receptor Gene T102C Polymorphism in Coronary Artery Disease and Serum Lipid Level

BACKGROUND AND OBJECTIVES: The 5-HT2A receptor is one of the main mediators of a serotonin-evoked coronary artery contraction. This is because vasoconstriction is selectively blocked by the 5-HT2 receptor antagonist, with the 5-HT2A receptor gene mRNA being detected in spastic coronary arteries. The relationship between the T102C polymorphism of the 5-HT2A receptor gene and the response to the 5-HT2A antagonist (clozapine) has recently been established, suggestive of a functional implication. Previous studies have observed an association between low cholesterol levels and mental disorders, but the underlying cause has not been determined. It has been established that the T102C polymorphism of the 5-HT2A serotonin receptor gene and a variety of psychological problems are related, but the relationship between the serum lipid level and this genetic polymorphism has not been reported. We investigated the influence of this polymorphism on coronary artery disease, including vasospastic angina and the clinical parameters, such as the lipid profile. SUBJECTS AND METHODS: After a diagnostic angiography was performed, the genotype was identified from the genomic DNA extracted from the peripheral blood of 646 patients without specific psychiatric diseases. RESULTS: There were no differences in the genotype frequencies between coronary artery disease, coronary artery disease with vasospasm, and the normal control groups, even from a subgroup analysis of the clinical parameters. Contrary to previous reports, the genotype distribution was not related to a myocardial infarction or hypertension. The lipid profile analysis showed significantly lower total cholesterol (193.5 vs. 202.1mg/dL, p=0.016) and HDL-cholesterol (42.7 vs. 46.2mg/dL, p=0.003) levels in the CC genotype than the other genotypes, and the frequencies of CC genotype showed a significantly decreasing trend between the HDL-cholesterol (p=0.003) and total cholesterol (p=0.003) quartiles. From a multivariate analysis, only the HDL-cholesterol level was significantly associated with a lower frequency of the CC genotype (p=0.006). CONCLUSION: The T102C polymorphism is not related to coronary artery disease, including vasospasm of the coronary artery, but the CC genotype of this polymorphism is related to low HDL-cholesterol. We identified a novel genetic polymorphism of the serotonin receptor, which affects the HDL-cholesterol level. Because previous observational studies have shown an association between low cholesterol levels and mental disorders, our data should be considered when analyzing the serum lipid levels and serotonin receptor function in humans.

Serotonin(5-HT): can it be a cause in overactive bladder

PURPOSE: The purpose of this study is to investigate in vitro the effects of serotonin on the rat detrusor. In particular, this study examines what drugs inhibit the serotonin-induced detrusor contractions. MATERIALS AND METHODS: Isometric tension changes of isolated rat bladder muscle strips were recorded in an organ bath using a force transducer. Acute effects of serotonin (0.0001-0.01mM) were assessed on resting tension. Electrical field stimulation (EFS), bethanechol (0.0001-0.01mM), ATP (1-3mM) or KCl(63.5-254mM)-induced contractions using application in organ bath were compared with serotonin-induced contractions. In order to examine the action mechanism of serotonin-induced stimulation, EFS, bethanechol, ATP or KCl-induced contraction under serotonin (0.001mM) was assessed and serotonin (0.001 to 0.1mM) was cumulatively added to the organ bath following pre-incubation with propranolol, ketanserine, tropisetron, propiverine, sodium nitroprusside or doxazocin. RESULTS: There are two phases to the serotonin-induced responsean initial transient contraction and a prolonged tonic phase. Serotonin produced a reversible and dose-dependent contraction of the detrusor strips. Responses to bethanechol significantly increased with a concentration of 0.001mM serotonin (p<0.05). There was no effect on the responses to ATP, KCl, or EFS under 0.001mM serotonin. The 5-HT2 receptor is mainly responsible for serotonin-induced contractions of the detrusor (p<0.05), while the 5-HT1 receptor is partially responsible. Doxazocin and propiverine each significantly suppressed the responses to serotonin, while sodium nitroprusside and tropisetron each had no effect (p<0.05). CONCLUSIONS: Because the 5-HT2 antagonist blocked the effect of serotonin-induced bladder contractions and the stimulation of the adrenoreceptors, the 5-HT2 antagonist seems to improve lower urinary tract symptoms.

Nefazodone and Associated Perceptual Disturbance : A Report of Four Cases

Nefazodone, a newer antidepressant is a phenylpiperazine derivative that inhibits the reuptake of both norepinephrine and serotonin, and antagonizes 5-HT2A and alpha1 adrenergic receptors. Compared with SSRIs nefazodone caused the fewer activating symptoms, adverse gastrointestinal effects(nausea, diarrhea, anorexia) and adverse effects of sexual function, but is associated with the more dizziness, dry mouth, constipation, visual disturbances and confusion. We report on 4 cases of visual disturbances and hallucinations in patients taking nefazodone. 1) Nefazodone, as a 5-HT2A antagonist, might induce visual disturbances. 2) mCPP, metabolite of nefazodone might contribute to the hallucination through action on 5-HT receptor. 3) Dopaminergic enhancing activity of nefazodone might cause hallucination. The case report raises the possibility that dose-related perceptual disturbances may exist with nefazodone. The fact emphasizes the need to pay close attention to all possible drug interactions, particularly in patients treated with multiple psychoactive agents, older patients, and patients with decreased hepatic function.

Association between Schizophrenia and the T102C Polymorphism of the 5-HT2A

The 5-HT2A receptor is of great interest for research into schizophrenia and psychopharmacology in light of the observation that schizophrenic patients has 5-HT cortical-subcortical imbalance and atypical antipsychotic clozpine has 5-HT2A antagonists properties. An significant association between schizophrenia and the T102C polymorphism of the gene for 5-HT2A receptor has been reported. In this study, we investigated an association between schizophrenia and the T102C polymorphism of the gene for 5-HT2A receptor in Korean schizophrenic patients. The subjects consisted of 139 schizophrenic patients and 88 normal controls. Genomic DNA was amplified by PCR and digested with MsPI. The uncutt product identified allele 1(nucleotide sequence TCT) ; digested products of 216bp and 156bp identified allele 2(nucleotide sequence TCC). The allele frequencies and the genotypic distribution of 5-HT2A receptor gene were not significantly different between schizophrenic patients and normal controls. Since allele frequencies of the T102C polymorphism may differ between individuals of different ethnic backgrounds, it needs to be conducted in an advanced research.

Effect of 5-HT2c Receptor Modulation on the m-Chlorophenlpiperazine-Induced Hypoactivity / 대한정신약물학회지

It was aimed to investigate the effect of 5-HT2C receptor modulation on the rat behavioral responses induced by 1-(m-chlorophenyl) piperazine(mCPP), a major metabolite of trazodone. The animal activities(ambulation, stereotypy and total activity) were measured for 3 hours following mCPP administration, using an animal activity meter which accumulates the frequency of light beam interruption. mCPP(1-10 mg / kg, i.p.) induced dose-dependent decreases in ambulation and stereotypy, consequently leading to hypoactivity. The hypoactivity induced by mCPP(1mg / kg, i.p.) was significantly inhibited by pretreatment with mianserin(1mg / kg, i.p.), an antagonist with high affinity for 5-HT2C receptor, whereas pretreatment with 5-HT2 antagonists, ketanserin and ritanserin(1mg / kg, i.p., respectively) was without effect. Furthermore, long-term pretreatment with imipramine(10mg / kg, i.p., b.i.d. for 2 weeks) markedly attenuated the mCPP-induced hypoactivity. Mianserin and imipramine in the absence of mCPP did not increase the animal activity. Taken together, these results indicate that the mCPP-induced hypoactivity is mediated by 5-HT2C receptor, and that selective 5-HT2C antagonists and down regulation of 5-HT2C receptor might be useful for inhibiting the mCPP-induced hypoactivity.