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Modulation of apomorphine-induced rotations in unilaterally 6-hydroxydopamine lesioned rats by cholinergic agonists
Abstract:
In the present study, we examined the effects of the agonists and antagonists of cholinergic receptors on central dopaminergic function using the 6-hydroxydopamine model of dopamine receptor supersensitivity. Unilateral lesioning of the substantia nigra with 6-hydroxydopamine was carried out in Wistar rats. Two weeks after surgery, the rats were tested for the presence of dopaminergic supersensitivity by their response to the dopamine receptor agonist, apomorphine. Apomorphine-induced rotations were significantly reinforced by the muscarinic receptor antagonist, atropine. In contrast to atropine, the muscarinic receptor agonist oxotremorine attenuated apomorphine's effects. Acute treatment of nicotine significantly reduced apomorphine-induced rotations. However, when increasing doses of nicotine were given for nine days, the rotations of the nicotine-dependent rats were significantly enhanced. So the fact that both muscarinic and nicotinic cholinergic activity could modulate apomorphine-induced rotations was readily apparent in these experiments.