Lateral striatal cholinergic mechanisms involved in oral motor activities in the rat

These experiments were undertaken to determine if local injection of pilocarpine in the neostriatum of the rat produces oral motor activities that are similar to those produced by systemic administration. In the first experiment, IP administration of 2.0-8.0 mg/kg pilocarpine increased chewing movements and tongue protrusions. In the second experiment, chronic guide cannulae were implanted bilaterally in ventromedial or ventrolateral striatum, and rats were injected with saline, 30, and 60 micrograms pilocarpine (per side). A dose-related increase in vacuous chewing was induced by injections of pilocarpine in the ventrolateral but not the ventromedial striatum. Tongue protrusions were induced by injections of pilocarpine into the ventromedial and the ventrolateral striatum. A third experiment demonstrated that this response was blocked completely by 10 micrograms scopolamine co-administered via the same cannulae, but the response was not reduced significantly by 10 micrograms haloperidol. These results indicate that ventrolateral striatal cholinergic mechanisms are involved in oral motor activities in the rat. This syndrome may provide a model for human clinical phenomena such as parkinsonian tremor.