Tolerance following the repeated administration of high doses of phencyclidine: no relation to central catecholamine depletion.

The tolerance which develops following the repeated administration of phencyclidine has been attributed to both pharmacological and behavioral adaptations. In the present study, the possibility that neurochemical alterations induced by the repeated administration of phencyclidine might account for some portion of the observed tolerance was examined. Specifically, it was postulated that the repeated administration of high doses of phencyclidine might result in long lasting depletion of central catecholamine stores and that this neurochemical perturbation might result in tolerance to the drug's effects. It was observed that phencyclidine disrupted the performance of rats on a fixed-interval schedule maintained by water presentation. The repeated administration of high doses of phencyclidine (but not of a comparable volume of saline) during a period when subjects were not engaged in the fixed-interval task resulted in the development of a long lasting tolerance, but this tolerance could not be accounted for in terms of a depletion of central catecholamine stores.