Effects of striatal injections of 8-bromo-cyclic-AMP on pilocarpine-induced tremulous jaw movements in rats

Abstract

Previous work has suggested that muscarinic agonist-induced jaw movements in rats were related to stimulation of M4 receptors, and that these movements could be suppressed by a full D1 agonist. In view of the involvement of cyclic-adenosine monophosphate (c-AMP) mechanisms in the response to stimulation of these two receptors, the present study investigated the effects of 8-bromo-c-AMP, which is a cell permeable analogue of c-AMP. In the first experiment, it was shown that local infusion of 8-bromo-c-AMP directly into ventrolateral striatum (VLS) was able to suppress the jaw movements induced by pilocarpine. The suppressive effects of 8-bromo-c-AMP occurred within a dose range of 5.0–10.0 μg. Injections of the highest dose of 8-bromo-c-AMP (10.0 μg) directly into the neocortex overlying the VLS had no significant effects on pilocarpine-induced jaw movements. These data demonstrate that mimicking the effects of c-AMP by administration of 8-bromo-c-AMP can suppress cholinomimetic-induced jaw movements. In addition, the present results suggest that one manifestation of the acetylcholine/dopamine interaction in striatum is that M4 and D1 receptors may interact to regulate c-AMP production.