Majallah-i Dānishgāh-i ̒Ulūm-i Pizishkī-i Bābul (Oct 1999)
The effects of Nicotine on licking behavior induced by Apomorphine in rats
Abstract
Objective: The purpose of the present study was to determine the possible interaction of nicotine or muscarinic receptor mechanism(s) with the licking behavior induced by apomorphine in rats. Methods: Rats (150-250 g) were treated with saline or different doses of apomorphine and nicotine, mecamylamine, hexamethonium and atropine. Licking was recorded during a period of 60 min dafter injection. One and two-way ANOVA followed by Newman-Keuls test were used for data analysis. Difference with P<0.05 between experimental groups at each point was considered statistically significant. Findings: In present study, the dopaminergic receptor agonist apomorphine (0.1, 0.25 and 0.5 mg/kg) induced a dose-dependent licking in rats. Nicotine administration (0.025-250 mg/kg) altered the apomorphine-induced licking. The lower doses of nicotinic (0.05 and 0.5 mg/kg) increased the apomorphine response while the higher dose (250 mg/kg) reduced it. The anti-muscarinic drug atropine (2.5 and 5 mg/kg) reduced the effects of apomorphine or nicotine plus apomorphine. The central nicotine receptor antagonist mecamylamine (0.05, 0.25 and 0.5 mg/kg) also reduced the response induced by apomorphine alone or together with nicotine. However, the peripheral nicotinic receptor antagonist hexamethonium (2.5, 5 and 10 mg/kg) reduced the response induced by nicotine plus apomorphine but not that elicited by apomorphine alone. Conclusion: The results indicate that the nicotinic receptor mechanism(s) may interact with apomorphine-induced licking in rats. Although central nicotinic and cholinergic mechanisms may be involved in the licking induce Med by apomorphine, peripheral nicotinic mechanism may be involved in the increased apomorphine effect induced by nicotine.
