Differences in central and peripheral responses to oxotremorine in young and aged rats.

Few studies have investigated the pharmacological response of agents that act on the cholinergic system from the point of view of age. The present article investigated central responses (tremor) and peripheral responses (chromodacryorrhea) subsequent to the administration of oxotremorine to young (3-6 months of age) and aged rats (24-30 months of age). The aged rats presented greater duration and intensity of tremor in three doses utilized (0.25, 0.5, and 1.0 mg/kg) compared to young rats. These two groups of animals did differ in latency for the onset of the tremor. The aged rats presented more intense chromodacryorrhea than the young rats in all utilized doses. These data are indicative that both responses--central and peripheral--are affected by aging, possibly as a result of pharmacokinetic alterations and/or alterations in functionality of the cholinergic system in aged rats.