Radial-arm maze performance in rats is impaired by a combination of nicotinic-cholinergic and D₂ dopaminergic antagonist drugs

Abstract

Performance on the radial-arm maze depends on the integrity of both cholinergic and dopaminergic systems. We have previously found that administration of either the nicotinic-cholinergic antagonist, mecamylamine, or the muscarinic-cholinergic antagonist, scopolamine, impairs choice accuracy in the radial-arm maze. Co-administration of the dopaminergic antagonist, haloperidol, ameliorated the performance deficit caused by scopolamine but exacerbated the deficit caused by mecamylamine. Furthermore, antagonism of the effect of scopolamine is due specifically to blockade of D₁ receptors. In the present experiment behaviorally subthreshold doses of mecamylamine and the D₂ antagonist raclopride impaired maze performance when administered together. No interactive effects were observed between mecamylamine and the D₁ antagonist SCH 23390. Although several of the drug treatments studied significantly increased choice latency, an index of motor behavior, there was no perfect relationship between choice accuracy and choice latency. These data indicate that nicotinic-cholinergic and muscarinic-cholinergic systems interact selectively and differentially with D₁ and D₂ dopaminergic systems.