Circadian periodicity of pituitary adrenal function after p chlorophenylalanine administration in the rat

Two days after a single or repeated administration of p chlorophenylalanine (p CPA; 316 mg/kg i.p.) in the rat, a marked diminution to 20% of control levels of brain 5 hydroxytryptamine, partial but not complete abolition of the circadian pituitary adrenal rhythm and a profound decrease in adrenal responsiveness to ether stress or exogenous adrenocorticotrophin were found. Pituitary adrenal activity in unstressed or stimulated animals was assessed by the level of corticosterone in plasma and the corticosteroid production by adrenal tissue in vitro. The effect of p CPA administration on changes in pituitary adrenal periodicity were concomitant with a reduction in food intake and body growth and a pronounced increase in adrenal weight. In the light of the marked functional alterations after p CPA treatment, the proposed relationship between decreased brain 5 hydroxytryptamine content and pituitary adrenal periodicity is questioned.