The acute and chronic administration of the 5-HT(2B/2C) receptor antagonist SB-200646A significantly alters the activity of spontaneously active midbrain dopamine neurons in the rat: An in vivo extracellular single cell study.
This study examined the effect of the acute and chronic administration of the 5-HT(2B/2C) receptor antagonist N-(1-methyl-5-indolyl)-N'-(3-pyridyl) urea hydrochloride (SB-200646A) on the activity of spontaneously active DA cells in the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA) in anesthetized, male Sprague-Dawley rats. This was accomplished using in vivo extracellular single cell recording. The i.v. administration of 4-16 mg/kg of SB-200646A significantly increased the firing rate and % events as bursts in spontaneously active VTA DA neurons and significantly increased the % events as burst in SNC DA neurons. The acute i.p. administration of 20 and 40 mg/kg of SB-200646A significantly increased the number of spontaneously active VTA DA neurons when compared with vehicle-treated controls. The acute administration of 10 mg/kg of SB-200646A significantly increased the coefficient of variation in spontaneously active SNC and DA neurons when compared with vehicle-treated controls. However, the acute i.p. administration of 20 mg/kg of SB-200646A significantly decreased the degree of bursting of VTA DA neurons. Similary, chronic i.p. administration of 10 mg/kg of SB-200646 did not significantly alter firing, whereas chronic administration of 20 mg/kg of SB-200646A or 20 mg/kg of clozapine significantly decreased the number of spontaneously active VTA DA neurons when compared with vehicle-treated controls. The SB-200646A-induced decrease in the number of spontaneously active VTA DA neurons was reversed by the i.v. administration of (+)-apomorphine or (-)-baclofen. The chronic i.p. administration of either 10 or 20 mg/kg of SB-200646A did not significantly alter the firing pattern of spontaneously active SNC DA neurons. However, the chronic administration of 20 mg/kg of SB-200646A significantly increased the degree of bursting in VTA DA neurons when compared with vehicle. Overall, the acute and chronic administration of SB-200646A produces in vivo electrophysiological effects, resembling that of atypical antipsychotic drugs.
GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow, Essex CM19 5AW, UK.
Thomas P
TP
Blackburn
Katsuaki
K
Suzuki
Charles R
CR
Ashby
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004298:Dopamine / Q000378:metabolism; D004594:Electrophysiology; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D008636:Mesencephalon / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology*; D013997:Time Factors; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology
D007211:Indoles; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists; C080864:N-(1-methyl-5-indolyl)-N'-(3-pyridyl)urea; D014508:Urea; D004298:Dopamine