A comparison of the discriminative stimulus properties of phencyclidine, given intraperitoneally or intraventricularly in rats.

Rats trained to discriminate intraperitoneally injected phencyclidine (PCP) from saline in a two-lever operant procedure distributed most of their responses on the phencyclidine lever after administration of 150 or 300 micrograms of phencyclidine into a lateral ventricle. This demonstrated that the discriminative stimulus properties of phencyclidine were centrally mediated. On the other hand, the potency of phencyclidine was increased by no more than about 7-fold from intraperitoneal to intraventricular administration. This suggests that either periventricular sites are not involved in mediating the discriminative stimulus properties of phencyclidine or that absorption of phencyclidine to relevant sites in the brain is not markedly enhanced by intraventricular administration.