title: Serotonergic afferent regulation of the basic physiology and pharmacological responsiveness of nigrostriatal dopamine neurons.
abstract: The electrophysiological responsiveness of nigrostriatal dopamine (DA) neurons to dorsal raphe stimulation and to systemic administration of serotonin (5-HT) selective compounds was examined in chloral hydrate-anesthetized rats. Electrical stimulation of the dorsal raphe selectively inhibited the firing rate of slowly firing (less than 4 spikes/sec) DA neurons. The 5-HT-1A agonists 8-hydroxy-2-(di-n-propylamino)tetralin and 5-methoxy-N,N-dimethyltryptamine preferentially increased the firing rate of slowly firing DA neurons, but did not alter the responsiveness of these cells to quinpirole-induced inhibition of firing rate. This increase in firing rate was not observed following depletion of brain 5-HT by the neurotoxin 5,7-dihydroxytryptamine. The 5-HT-1B agonists trifluoromethylphenylpiperazine and M-chlorophenylpiperazine had only weak inhibitory effects on the firing rates of DA neurons, and also failed to alter the responsiveness of DA neurons to quinpirole-induced inhibition. Depletion of brain 5-HT (greater than 80%) by either para-chlorophenylalanine or 5,7-dihydroxytryptamine eliminated the rate-dependent nature of quinpirole-induced inhibition of nigrostriatal DA neurons, while having limited effects on the basal electrophysiological activity of these cells. These data suggest that 5-HT systems exert subtle influences on the activity and pharmacological responsiveness of nigrostriatal DA neurons.
authors.affiliation: Laboratory of Neurophysiology, Center for Cell Biology Sinai Research Institute, Detroit, Michigan.
authors.forename: M D
authors.initials: MD
authors.lastname: Kelland
authors.forename: A S
authors.initials: AS
authors.lastname: Freeman
authors.forename: L A
authors.initials: LA
authors.lastname: Chiodo
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D015259:Dopamine Agents / Q000494:pharmacology; D004594:Electrophysiology; D004873:Ergolines / Q000494:pharmacology; D010134:Fenclonine / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*
chemical_list: D015259:Dopamine Agents; D004873:Ergolines; D019257:Quinpirole; D012701:Serotonin; D010134:Fenclonine; D004298:Dopamine