The ability of nicotine, to induce grooming in rats was studied, Grooming w
as induced by i.p. injection of different doses (0.0675-0.5 mg/kg) of nicot
ine to rats. The effect was dose-dependent. However, the response was decre
ased with increasing doses of the drug from 0.25-0.5 mg/kg. Administration
of the dopamine (DA) D-1/D-2 receptor agonist apomorphine (0.025-5 mg/kg, i
.p.) also caused grooming in a dose-dependent manner. High doses of apomorp
hine (0.1-0.5 mg/kg, i.p.) also induced a lower degree of response. Combina
tion of a low dose of nicotine (0.0675 mg/kg) with different doses of apomo
rphine did not show any interaction. However, there was an interaction betw
een a high dose of nicotine and apomorphine. Thus, combination of a higher
dose of nicotine (0.125 mg/kg) with apomorphine, reduced apomorphine-induce
d grooming.
The muscarinic receptor antagonist atropine (5 and 10 mg/kg), peripheral ni
cotinic receptor antagonist hexamethonium (5 and 10 mg/kg), central nicotin
ic receptor antagonist mecamylamine (I and 3 mg/kg) and D-1 DA receptor ant
agonist SCH23390 (0.05 and 0.1 mg/kg) all decreased the response to nicotin
e. Atropine, mecamylamine and SCH23390 by themselves reduced spontaneous gr
ooming. It is concluded that nicotine elicits grooming indirectly through a
possible D-1 dopaminergic mechanism. However, muscarinic and nicotinic cho
linergic mechanism(s) may be involved.