title: Effect of acute and chronic administration of the selective 5-HT2C receptor antagonist SB-243213 on midbrain dopamine neurons in the rat: an in vivo extracellular single cell study.
abstract: In this study, we examined the effect of the acute and chronic administration of the selective 5-HT2C receptor antagonist SB-243213 (SB) on the activity of spontaneously active dopamine (DA) cells in the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA) in anesthetized, albino, male Sprague-Dawley rats. This was accomplished using the technique of in vivo extracellular single cell recording. The acute i.v. administration of SB-243213 (0.025-3.2 mg/kg) did not significantly alter the basal firing rate or pattern of either spontaneously active SNC or VTA DA neurons compared to vehicle-treated controls. The acute i.p. administration of either 1 or 10 mg/kg of SB-243213 did not significantly alter the number of spontaneously active DA cells in the SNC or VTA compared to vehicle-treated controls, whereas the 3 mg/kg dose only significantly decreased the number of spontaneously active VTA DA neurons. Overall, the 1 mg/kg dose of SB-243213 did not significantly alter the firing pattern of either SNC or VTA DA neurons compared to vehicle-treated controls. In contrast, the 3 mg/kg dose significantly altered the firing pattern of SNC DA neurons, whereas the 10 mg/kg dose altered the firing pattern of DA neurons in both the SNC and VTA. The repeated i.p. administration (21 days) of 1, 3, and 10 mg/kg of SB-243213 or 20 mg/kg of clozapine produced a significant decrease in the number of spontaneously active DA cells in the VTA compared to vehicle-treated controls. The decrease in the number of spontaneously active VTA DA cells was not reversed by the i.v. administration of (+)-apomorphine (50 microg/kg). The repeated administration of either 1 or 3 mg/kg of SB-243213 had minimal effects on the firing pattern of either SNC or VTA DA neurons. In contrast, the firing pattern of VTA DA neurons was significantly altered by 10 mg/kg dose of SB-243213. Overall, our results indicate that antagonism of the 5-HT2C receptor alters the activity of midbrain DA neurons in anesthetized rats and suggest that SB-243213 has an atypical antipsychotic profile following chronic administration.
mesh_terms: D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000200:Action Potentials / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002452:Cell Count / Q000379:methods; D003024:Clozapine / Q000494:pharmacology; D003505:Cyclodextrins / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D004347:Drug Interactions; D006220:Haloperidol / Q000494:pharmacology; D007211:Indoles / Q000008:administration & dosage*; D008297:Male; D009474:Neurons / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D011725:Pyridines / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology; D013378:Substantia Nigra / Q000166:cytology*; D017557:Ventral Tegmental Area / Q000166:cytology*; D047392:beta-Cyclodextrins
chemical_list: D003505:Cyclodextrins; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D007211:Indoles; D011725:Pyridines; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D003024:Clozapine; D006220:Haloperidol; D001058:Apomorphine; C406343:SB 243213; D004298:Dopamine