Acute and chronic phencyclidine administration effects on the conversion of 3H-tryptophan to 3H-serotonin in rat forebrain.

Acute administration of phencyclidine hydrochloride (PCP) resulted in a dose-responsive decrease in the conversion of 3H-tryptophan to 3H-serotonin (3H-5-HT) in rat forebrain. Subsequent experiments measured the effect of a subthreshold dose of PCP (4 mg/kg) daily for one, seven, or four-teen days on this index of 5-HT turnover. Although single administration again had no effect at this dose, repeated administration for seven days resulted in a 37% decrease in 5-HT turnover. However, after fourteen days of administration this index was not significantly different from saline controls The possible significance of these findings are discussed in relation to reported alterations in PCP-induced behaviors observed with chronic administration.