[Nicotine-induced ambulatory stimulant effect and its reverse tolerance].
Nicotine-induced ambulatory stimulant effect and its reverse tolerance produced by daily administration of nicotine in rats were investigated. Nicotine (0.5 and 1.0 mg/kg, sc) increased the ambulatory activity, which was enhanced by the daily administration of nicotine. Although total ambulatory activity and drinking behavior during 20 h (from 13:00 to 9:00) following daily administration of nicotine (1.0 mg/kg, sc) for 7 successive days decreased, these behaviors returned to the control levels after the nicotine-treatment period. Moreover the periods (tau s) of the ambulatory activity and drinking were not changed by daily injections of nicotine (1.0 mg/kg, sc) for 6 successive days. The enhancement of the ambulatory stimulant effect produced by daily injections of nicotine (0.5 mg/kg) was antagonized by mecamylamine (0.2 mg/kg) and haloperidol (0.05, 0.1 and 0.2 mg/kg), which were subcutaneously administered at 20 min before injections of nicotine. These results suggest that the enhancement of nicotine-induced ambulatory stimulant effect by the daily administration of nicotine is concerned with central dopaminergic stimulation through the nicotinic acetylcholine receptor in the rat brain.
Kita
T
T
Department of Pharmacology, Nara Medical University, Kashihara, Japan.
Okamoto
M
M
Nakashima
T
T
D000818:Animals; D004326:Drinking / Q000187:drug effects; D004361:Drug Tolerance; D006220:Haloperidol / Q000494:pharmacology; D007279:Injections, Subcutaneous; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009538:Nicotine / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical
D008464:Mecamylamine; D009538:Nicotine; D006220:Haloperidol