title: Light-dark variation in response to chronic nicotine treatment and the density of hypothalamic alpha-bungarotoxin receptors.
abstract: Chronic nicotine administration increased locomotor activity during the light, but not the dark, in rats maintained on a 12:12-hr light/dark cycle, but the period and peak of the circadian rhythm (CR) were not affected. In Experiment I, 24 male rats were implanted with battery-operated telemeters and locomotor activity was continuously measured for 10 days before and 10 days after the implantation of osmotic mini-pumps which delivered 0, 0.5, 3.0 or 10 mg/kg/day of (+/-)-nicotine tartrate. Nicotine increased locomotor activity during the light in a dose-dependent manner. Tolerance to the stimulant effects of nicotine during the light occurred in 5-6 days. To determine if the stimulant properties of nicotine were associated with light as opposed to disruption by the environmental stimuli normally present during the day in our animal facility, a second experiment was conducted in which rats were treated with saline or 10 mg/kg/day (+/-)-nicotine di(+)hydrate tartrate and maintained on a reversed light/dark cycle. Again nicotine increased activity during the light (21:00-09:00) but not the dark (09:00-21:00). In a third experiment, the density of alpha-bungarotoxin binding sites was found to be significantly decreased when animals were sacrificed at 06:00 in comparison with animals sacrificed at 10:00 and 14:00.
authors.affiliation: Research Division, Boys Town National Research Hospital, Omaha, NE 68131.
authors.forename: B J
authors.initials: BJ
authors.lastname: Morley
authors.forename: L L
authors.initials: LL
authors.lastname: Garner
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D004343:Drug Implants; D007031:Hypothalamus / Q000187:drug effects*; D008027:Light; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000187:drug effects* / Q000378:metabolism; D011978:Receptors, Nicotinic; D013686:Telemetry; D013997:Time Factors; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579165:Chrna7 protein, rat; D004343:Drug Implants; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine