Effect of p-chlorophenylalnine on the loss and maintenance of tolerance to ethanol.

Rats were rendered tolerant to the motor-impairing effects of ethanol by daily oral administration. Subsequently, ethanol was withdrawn and the effect of p-chlorophenylalanine (p-CPA) on tolerance loss was examined. In two separate studies it was demonstrated that p-CPA, in a dosage regimen that produces extensive depletion of brain serotonin (5-HT), accelerated tolerance loss. These experiments suggest that at least part of p-CPA's inhibitory effect on net tolerance development to ethanol can be accounted for by its accelerating effect on tolerance loss; however, an inhibitory effect on tolerance acquisition cannot be excluded. On the other hand, once tolerance was established, p-CPA did not affect the maintenance of tolerance to ethanol.