• The Korean Journal of Physiology and Pharmacology
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• v.20 no.6
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• pp.605-611
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• 2016

Ketamine is an anesthetic with hypertensive effects, which make it useful for patients at risk of shock. However, previous ex vivo studies reported vasodilatory actions of ketamine in isolated arteries. In this study, we reexamined the effects of ketamine on arterial tones in the presence and absence of physiological concentrations of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) by measuring the isometric tension of endothelium-denuded rat mesenteric arterial rings. Ketamine little affected the resting tone of control mesenteric arterial rings, but, in the presence of 5-HT (100~200 nM), ketamine ($10{\sim}100{\mu}M$) markedly contracted the arterial rings. Ketamine did not contract arterial rings in the presence of NE (10 nM), indicating that the vasoconstrictive action of ketamine is 5-HT-dependent. The concentration-response curves (CRCs) of 5-HT were clearly shifted to the left in the presence of ketamine ($30{\mu}M$), whereas the CRCs of NE were little affected by ketamine. The left shift of the 5-HT CRCs caused by ketamine was reversed with ketanserin, a competitive 5-$HT_{2A}$ receptor inhibitor, indicating that ketamine facilitated the activation of 5-$HT_{2A}$ receptors. Anpirtoline and BW723C86, selective agonists of 5-$HT_{1B}$ and 5-$HT_{2B}$ receptors, respectively, did not contract arterial rings in the absence or presence of ketamine. These results indicate that ketamine specifically enhances 5-$HT_{2A}$ receptor-mediated vasoconstriction and that it is vasoconstrictive in a clinical setting. The facilitative action of ketamine on 5-$HT_{2A}$ receptors should be considered in ketamine-induced hypertension as well as in the pathogenesis of diseases such as schizophrenia, wherein experimental animal models are frequently generated using ketamine.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.6
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• pp.295-301
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• 2003

Striatum plays a crucial role in the movement control and habitual learning. It receives an information from wide area of cerebral cortex as well as an extensive serotonergic (5-hydroxytryptamine, 5-HT) input from raphe nuclei. In the present study, the effects of 5-HT to modulate synaptic transmission were studied in the rat corticostriatal brain slice using in vitro extracellular recording technique. Synaptic responses were evoked by stimulation of cortical glutamatergic inputs on the corpus callosum and recorded in the dorsal striatum. 5-HT reversibly inhibited coticostriatal glutamatergic synaptic transmission in a dose-dependent fashion (5, 10, 50, and $10{\mu}M$), maximally reducing in the corticostriatal population spike (PS) amplitude to $40.1{\pm}5.0$% at a concentration of $50{\mu}M$ 5-HT. PSs mediated by non-NMDA glutamate receptors, which were isolated by bath application of the NMDA receptor antagonist, d,l-2-amino-5-phospohonovaleric acid (AP-V), were decreased by application of $50{\mu}M$ 5-HT. However, PSs mediated by NMDA receptors, that were activated by application of zero $Mg^{2+}$ aCSF, were not significantly affected by $50{\mu}M$ 5-HT. To test whether the corticostriatal synaptic inhibitions by 5-HT might involve a change in the probability of neurotransmitter release from presynaptic nerve terminals, we measured the paired-pulse ratio (PPR) evoked by 2 identical pulses (50 ms interpulse interval), and found that PPR was increased ($33.4{\pm}5.2$%) by 5-HT, reflecting decreased neurotransmitter releasing probability. These results suggest that 5-HT may decrease neurotransmitter release probability of glutamatergic corticostriatal synapse and may be able to selectively decrease non-NMDA glutamate receptor-mediated synaptic transmission.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.355-359
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• 2000

Cocaine induces immediate early gene expression and behavioral changes by blocking dopamine transporters in the terminals of nigrostriatal neurons in the striatum. The pharmacological role of serotonin 2/1C (5HT2/1C) receptors in cocaine-induced expression of zif268 (NGFI-A, egr1 and Krox-24) mRNA, a member of the zinc finger, was investigated using quantitative in situ hybridization histochemistry in vivo. Behavioral alterations induced by cocaine were also monitored in relation with blockade of the receptors. Systemic injection of ritanserin (1 mg/kg, s.c.), a 5HT2/1C receptor antagonist, did not reverse behavioral alterations and zif268 mRNA gene expression induced by 15 mg/kg cocaine, i.p., in the dorsal and ventral striatum. These data indicate that ritanserin-sensitive 5HT2/1C receptors are not necessary for cocaine-induced behavioral alterations and zif268 mRNA gene expression in the striatum.

• Molecules and Cells
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• v.20 no.1
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• pp.69-73
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• 2005

The flavonoid, quercetin, is a low molecular weight substance found in apple, tomato and other fruit. Besides its antioxidative effect, quercetin, like other flavonoids, has a wide range of neuropharmacological actions including analgesia, and motility, sleep, anticonvulsant, sedative and anxiolytic effects. In the present study, we investigated its effect on mouse 5-hydroxytryptamine type 3 ($5-HT_{3A}$) receptor channel activity, which is involved in pain transmission, analgesia, vomiting, and mood disorders. The $5-HT_{3A}$ receptor was expressed in Xenopus oocytes, and the current was measured with the two-electrode voltage clamp technique. In oocytes injected with $5-HT_{3A}$ receptor cRNA, quercetin inhibited the 5-HT-induced inward peak current ($I_{5-HT}$) with an $IC_{50}$ of $64.7{\pm}2.2{\mu}M$. Inhibition was competitive and voltage-independent. Point mutations of pre-transmembrane domain 1 (pre-TM1) such as R222T and R222A, but not R222D, R222E and R222K, abolished inhibition, indicating that quercetin interacts with the pre-TM1 of the $5-HT_{3A}$ receptor.

• Journal of Life Science
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• v.31 no.7
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• pp.662-670
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• 2021

Interstitial cells of Cajal (ICCs) are the pacemaking cells in the gastrointestinal (GI) muscles that generate the rhythmic oscillation in membrane potentials known as slow waves. In the present study, we investigated the effects of mirtazapine, a noradrenergic and serotonergic antidepressant, on pacemaking potential in cultured ICCs from the murine small intestine. The whole-cell patch-clamp configuration was used to record pacemaker potential in cultured ICCs. Mirtazapine induced pacemaker potential depolarizations in a concentration-dependent manner in the current clamp mode. Y25130 (a 5-HT3 receptor antagonist), RS39604 (a 5-HT4 receptor antagonist), and SB269970 (a 5-HT7 receptor antagonist) had no effects on mirtazapine-induced pacemaker potential depolarizations. Also, methoctramine, a muscarinic M₂ receptor antagonist, had no effect on mirtazapine-induced pacemaker potential depolarizations, whereas 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP), a muscarinic M₃ receptor antagonist, inhibited the depolarizations. When guanosine 5'-[β-thio] diphosphate (GDP-β-S; 1 mM) was in the pipette solution, mirtazapine-induced pacemaker potential depolarization was blocked. When an external Ca²⁺ free solution or thapsigargin, a Ca²⁺-ATPase inhibitor of the endoplasmic reticulum, was applied, the generation of pacemaker potentials disappeared, and under these conditions, mirtazapine induced pacemaker potential depolarizations. In addition, protein kinase C (PKC) inhibitor, calphostin C, and chelerythrine inhibited mirtazapine-induced pacemaker potential depolarizations. These results suggest that mirtazapine regulates pacemaker potentials through muscarinic M₃ receptor activation via a G protein-dependent and an external or internal Ca²⁺-independent PKC pathway in the ICCs. Therefore, mirtazapine can control GI motility through ICCs.

• Korean Journal of Biological Psychiatry
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• v.3 no.2
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• pp.262-268
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• 1996

It has been known that clozapine is more selective mesolimbic dopamin $D_2$ receptor antagonist and related to 5-HT receptor. In this study, we wxamined the plasma homovanillic acid(HVA), serotonin(5-HT), and 5-hydroxyindoleacetic acid(5-HIM) levels in refractory schizophrenics during clozapine treatment. And we assessed the effects of clozapine on these plasma monoamine metabolites and their association with psychopathology and treatment response. Eight refractory schizophrenic patients(DSM-IV) have entered the study for 3 months during clozapine treatment. Patients were admitted to the inpatient sevice and withdrawn from all neuroleptics for 7-14 days but exceptionally occasional doses of lorazepam was given if needed for behavioral control. The dose of clozapine was titrated as tolerated to 800mg/day. The plasma HVA. 5-HIM and 5-HT levels were measured before treatment and following 2nd week, 4th week, 8th week, and 12th during treatment. Psychopathology was assessed with Brief Psychiatric Rating Scale (BPRS) and Positive and Negative Synrome Scale(PANSS) before and during clozapine treatment. During clozapine treatment, no statistically significant changes were found in plasma HVA, 5-HIM, 5-HT levels, and HVA/5-HIM ratio between baseline and following 2nd week, 4th week, 8th week, 12th week. However, the change in plasma 5-HIAA/5-HT ratio from baseline to 4th week was statistically significant. Generally, changes of plasma HVA, 5-HIAA, 5-HT levels and HVA/5-HIAA ratio were not associated with psychopathology but 5-HIAA was associated with in positive symptoms and general psychopathology of PANSS. These results suggest that clozapine has been found to have relatively weak dopaminergic blokade and stronger serotonergic antagonism.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.347-353
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• 2000

It has been well documented that a massive release of not only glutamate but also other neurotransmitters may modulate the final responses of nerve cells to the ischemic neuronal injury. But there is no information regarding whether the release of monoamines is directly associated with synaptic vesicular proteins under ischemia. In the present study, it was investigated whether synapsin 1, syntaxin and SNAP-25 are involved in the release of 5-hydroxytryptamine $([^3H]5-HT)$ in glucose/oxygen deprived (GOD) rat hippocampal slices. And, the effect of NMDA receptor using DL-2-amino-5-phosphonovaleric acid (APV) on ischemia- induced release of 5-HT and the changes of the above proteins were also investigated. GOD for 20 minutes enhanced release of $[^3H]5-HT,$ which was in part blocked by the NMDA receptor antagonist, APV. The augmented expression of synapsin 1 during GOD for 20 minutes, which was also in part prevented by APV. In contrast, the expression of syntaxin and SNAP-25 were not altered during GOD. These results suggest that ischemic insult induces release of $[^3H]5-HT$ associated with synapsin 1, synaptic vesicular protein, via activation of NMDA receptor in part.

• The Korean Journal of Pain
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• v.26 no.2
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• pp.125-129
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• 2013

Background: 5-hydroxytryptamine 3 (5-HT3) receptors have been known to be associated with the modulation of nociceptive transmission. However, it is uncertain whether 5-HT3 plays a role in the antinociceptive or pronociceptive pathway for incisional pain. In this study, we evaluated the effects of palonosetron, a 5-HT3 receptor antagonist, on incisional pain in rats when administered intrathecally or intraplantarly. Methods: An intrathecal catheter was implanted through the cisterna magna and placed in the intrathecal space of rats. An incision in the plantaris muscle of the right hind paw was done under anesthesia with sevoflurane. Withdrawal thresholds were evaluated with the von Frey filament after 2 hours. Palonosetron (0.5 and 0.1 ${\mu}g$ intrathecally; 0.5 ${\mu}g$ intraplantarly) was administered and the thresholds were observed for 4 hours. Results: Mechanical hypersensitivity developed after the incision. Intrathecal palonosetron (0.5 ${\mu}g$ and 0.1 ${\mu}g$) did not alter the paw withdrawal threshold. Intraplantar palonosetron (0.5 ${\mu}g$) also did not change the paw withdrawal threshold. Conclusions: Intrathecal and intraplantar palonosetron (0.5 ${\mu}g$) had no effect on modulating the mechanical hypersensitivity in the incisional pain model of rats.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2930-2936
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• 2012

A three-dimensional pharmacophore hypothesis was developed for atypical antipsychotics in order to map common structural features of highly active compounds by using HipHop in CATALYST program. The pharmacophore hypotheses were generated using 12 compounds as training set and validated using 11 compounds as test set. The most predictive hypothesis (Hypo1) comprises five features viz. two hydrophobic regions, two hydrogen bond acceptor lipid and one aromatic ring. In the absence of information like crystallized structure of 5-$HT_{2A}$ receptor and binding mode of antipsychotics with 5-$HT_{2A}$ receptor, this hypothesis will serve as a potentially valuable tool in the design of novel atypical antipsychotics acting primarily at 5-$HT_{2A}$ and $D_2$ receptors.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.111-116
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• 2008

A piperazinylalkylisoxazole library containing 86 compounds was constructed and evaluated for the binding affinities to dopamine (D3) and serotonin (5-HT2A/2C) receptor to develop antipsychotics. Dopamine antagonists (DA) showing selectivity for D3 receptor over the D2 receptor, serotonin antagonists (SA), and serotonin-dopamine dual antagonists (SDA) were identified based on their binding affinity and selectivity. The analogues were divided into three groups of 7 DAs (D3), 33 SAs (5-HT2A/2C), and 46 SDAs (D3 and 5-HT2A/2C). A classification model was generated for identifying structural characteristics of those antagonists with different affinity profiles. On the basis of the results from our previous study, we conducted the generation of the decision trees by the recursive-partitioning (RP) method using Cerius2 2D descriptors, and identified and interpreted the descriptors that discriminate in-house antipsychotic compounds.