Effect of short- and long-term treatment with cocaine on rat brain tryptophan hydroxylase.

Short-term (5 days) treatment with cocaine (10 mg/kg, i.p.) inhibited the soluble tryptophan hydroxylase while the particulate enzyme was essentially unchanged. In contrast, long-term (45 days) treatment resulted in an increased activity of the particulate enzyme and a return to normal of the soluble enzyme activity.