NEOSTRIATAL NEURONS OF RATS CAN BE INFLUENCED BY CHOLECYSTOKININ-A RECEPTOR AGONISTS

The present study investigated the effects of agonists of the neuropep tide cholecystokinin (CCK) on neostriatal neurons in order to confirm the existence of CCK-A receptors in the rat caudate-putamen. Single un it activity was recorded in rats anaesthetized with urethane. The CCK- A receptor agonists A-71378 -Tyr(SO3H)-Nle-Gly-Trp-Nle-(N-methyl)Asp-P he-NH2), and A-71623 ys(epsilon-N-2-methylphenylamino-carbonyl)-Asp-(N - methyl)Phe-NH2, as well as the CCK-B receptor agonist Suc-CCK-4 (Suc -Trp-(N-methyl)Nle-Asp-Phe-NH2) were iontophoretically administered wi th multibarrel capillaries. About one-third of the neurons responded t o the CCK-A receptor agonists. Excitatory effects predominated. The CC K-B receptor agonist also induced mainly increases in the neuronal fir ing. Several neurons were affected by both types of agonists. The resu lts suggest that in the rat neostriatum not only CCK-B receptors, but also CCK-A receptors seem to mediate the effects of cholecystokinin.