title: Chronic nicotine differentially affects the function of nicotinic receptor subtypes regulating neurotransmitter release.
abstract: It is known that nicotine can activate several subtypes of release-regulating presynaptic nicotinic receptors (nAChRs) including those situated on central noradrenergic, dopaminergic, cholinergic and glutamatergic axon terminals. The objective of this study was to investigate the effects of chronic administration of (-)nicotine on the function of the above autoreceptors and heteroreceptors using rat superfused synaptosomes. In hippocampal synaptosomes prelabelled with [3H]noradrenaline (NA) the nicotine-evoked overflow of [3H]NA was higher in rats treated with nicotine for 10 days (via osmotic mini-pumps) than in vehicle-treated rats. In striatal synaptosomes, prelabelled with [3H]dopamine (DA), chronic nicotine did not modify the releasing effect of nicotine. No significant change was observed in experiments with synaptosomes from nucleus accumbens prelabelled with [3H]DA. Exposure of hippocampal synaptosomes prelabelled with [3H]choline to nicotine elicited release of [3H]acetylcholine; this effect was almost abolished in synaptosomes from animals administered nicotine for 10 days, suggesting down-regulation of nicotinic autoreceptors. In hippocampal synaptosomes prelabelled with [3H]D-aspartate, the releasing effect of epibatidine following chronic nicotine treatment did not differ from that in controls. The K+-evoked exocytotic release of the neurotransmitters tested was not modified by long-term nicotine administration. The results show that chronic nicotine differentially affects the function of release-regulating nAChR subtypes.
authors.affiliation: Sezione di Farmacologia e Tossicologia, Dipartimento di Medicina Sperimentale, Universitàdi Genova, Genova, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Grilli
authors.forename: Monica
authors.initials: M
authors.lastname: Parodi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Raiteri
authors.forename: Mario
authors.initials: M
authors.lastname: Marchi
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D026603:D-Aspartic Acid / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009538:Nicotine / Q000008:administration & dosage* / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000008:administration & dosage* / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D011188:Potassium / Q000008:administration & dosage / Q000494:pharmacology; D020033:Protein Isoforms / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000502:physiology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018377:Neurotransmitter Agents; D018722:Nicotinic Agonists; D020033:Protein Isoforms; D011725:Pyridines; D011978:Receptors, Nicotinic; D026603:D-Aspartic Acid; D009538:Nicotine; C082748:epibatidine; D000109:Acetylcholine; D011188:Potassium; D004298:Dopamine; D009638:Norepinephrine