Electrophysiological actions of nicotine on substantia nigra single units.
Extracellular recordings of single unit activity were made in the substantia nigra (SN) of chloral hydrate-anaesthetized rats. Dopaminergic neurones of the pars compacta (SNC) were stimulated by (-)-nicotine bitartrate (1.0 mg kg-1) given subcutaneously (s.c.). This action was prevented by the secondary amine mecamylamine HCl (2.0 mg kg-1 i.v.) but not by a ganglion-blocking dose of the bisquaternary compound chlorisondamine Cl (0.1 mg kg-1 i.v.). Mecamylamine reduced the spontaneous activity of dopaminergic neurones. Nicotine, when administered intravenously (2-128 micrograms kg-1 cumulative dose), also stimulated dopamine cells and this action was dose-related. Nicotine, administered intravenously, (2-128 micrograms kg-1 cumulative dose) markedly excited non-dopamine cells in the pars reticulata (SNR) in a dose-related manner. In rats pretreated with chlorisondamine (0.1 mg kg-1 i.v.), nicotine induced a small excitatory or depressant action, but the marked excitation was not seen. Mecamylamine (2 mg kg-1 i.v.) completely prevented the actions of nicotine. The results are consistent with a direct excitatory action of nicotine on dopaminergic neurones of the substantia nigra pars compacta. The pronounced excitatory action of systemically administered nicotine on non-dopamine cells of the pars reticulata appears to be of peripheral origin.
D000818:Animals; D002714:Chlorisondamine / Q000494:pharmacology; D004298:Dopamine / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D007275:Injections, Intravenous; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*
D008464:Mecamylamine; D009538:Nicotine; D002714:Chlorisondamine; D004298:Dopamine