The effects of striatal lesion on turning behavior and globus pallidus single unit response to dopamine agonist administration

In normal rats, globus pallidus neurons are excited by the systemic administration of postsynaptically active doses of apomorphine. The role of the striatum in mediating this phenomenon was examined by investigating the effects of apomorphine on neuronal activity in the globus pallidus and on turning behavior in rats with unilateral quinolinic acid lesions of the striatum. The lesion markedly reduced striatal choline acetyltransferase activity and GABA content and significantly attenuated apomorphine's effect on the activity of pallidal neurons. Both the extent of attenuation of the electrophysiological response of pallidal neurons in lesioned animals and the neurotoxin-induced decreases in choline acetyltransferase activity and GABA content in the caudal striatum were correlated with the degree of apomorphine-induced turning. The data indicate that striatopallidal neurons contribute to apomorphine's excitatory effect on the activity of pallidal neurons in normal animals.