In the present study, intraperitoneal (IP) administration of the dopaminerg
ic receptor agonist apomorphine (0.1, 0.25, and 0.5 mg/kg) induced a dose-d
ependent licking in rats. The intraperitoneal injection of the alpha(1)"' a
drenoceptor agonist phenylephrine (1-8 mg/kg) but not the alpha(2)-adrenoce
ptor agonist clonidine (0.025-0.05 mg/kg) decreased licking induced by apom
orphine. The alpha-adrenoceptor antagonists prazosin, phenoxybenzamine, and
yohimbine also reduced the apomorphine response significantly. The respons
e induced by phenylephrine was decreased by a dose of prazosin. The beta(1)
-adrenenocepor agonist dobutamine and beta(2)-adrenenocepor agonist salbuta
mol did not alter the apomorphine response. However, beta(2)-adrenenocepor
antagonists atenolol and propranolol reduced the apomorphine effect. It may
be concluded that alpha(1)- and possibly beta(1)-adrenoceptor mechanisms m
ay be involved in modulation of licking behavior. (C) 2000 Elsevier Science
Inc.