Accumulation of apomorphine in caudate nucleus and hippocampus of the rabbit.

Apomorphine concentration was assayed in the caudate nucleus, hippocampus and cerebellum of rabbits injected with various doses of the drug 30 min earlier. Apomorphine accumulation was dose-dependent but uneven in the structures tested: the accumulation in the caudate nucleus being approx. 5 times higher than in cerebellum. Pretreatment with haloperidol significantly depressed the accumulation of apomorphine in the caudate nucleus and hippocampus, but not in the cerebellum. The amount of apomorphine displaceable by haloperidol was approx. 10 times higher in the caudate nucleus than in the hippocampus. The results suggest the existence of small number of apomorphine binding sites in the hippocampus.