Effect of dopaminergic drugs on enhancement of the binding of quinuclidinyl benzilate by phencyclidine in vivo

Effect of central injection of phencyclidine on QNB accumulation and motor activity

The purpose of the present research was to determine if central administration of phencyclidine (PCP) would increase the in vivo accumulation of the muscarinic ligand, [3H]quinuclidinyl benzilate (QNB) in mouse brain as has been reported after peripheral administration of PCP. Secondly, in order to provide a behavioral reference against which to compare any biochemical changes, the effects of peripheral vs. central PCP administration on motor activity were compared. When given into the lateral ventricle (i.c.v.) 20 min before QNB, PCP increased the accumulation of QNB in brain striatum and cortex, but not cerebellum. This finding replicates results of previous studies in which the drug was given i.p. The dose required to enhance QNB binding after central injection was, on a mg/kg body weight basis, approximately 10-fold less than that previously found necessary after i.p. injection. In contrast, PCP given centrally was markedly more potent in the motor activity tests than when given i.p. In addition, the behaviorally effective dose (0.4 microgram) was substantially less than that needed for the QNB change (25.6 micrograms). Therefore, though PCP was more active in both measures after central than peripheral administration, the changes in QNB accumulation cannot, at this time, be related to changes in motor activity.