Phencyclidine-induced desensitization of striatal dopamine release

Increased release of dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) from slices of striatum of DBA/2J mouse in response to administration of phencyclidine (PCP) in vitro has been observed to be transient, despite continued exposure to PCP. To determinewhether this transient response was a result of depletion of releasable pools, toxicity or an adaptice response (desensitization), the recovery of the response to PCP was evaluated. Slices in the control condition were exposed to PCP (300 μM) during test-exposure only. Slices in the PCP pre-exposure condition, were exposed first to PCP (30 μM; pre-exposure) and subsequently to PCP (300 μM; test-exposure). During a washout period (0, 30, 60 or 120 min) between exposures to PCP, the slices were superfused in the absence of PCP. Pre-exposure to PCP diminished the subsequent response to test-exposure to PCP (49 and 37% of control for DA and DOPAC, respectively) after 0 min washout. Overflow of DA evoked by PCP returned towards control values but remained decreased (66% of control) after up to 120 min washout. However, overflow of DOPAC did return to control values after 60 min washout. Thus, the diminished dopaminergic response, resulting from continued exposure to PCP was not due to depletion of the releasable pool or cytotoxicity but rather to a dynamic adaptive response of the dopaminergic neuron to PCP.