Adrenocortical control of phenylethanolamine-N-methyl transferase and monoamine oxidase activity in the ground squirrel (Citellus citellus) during the summer.

Phenylethanolamine-N-methyl transferase (PNMT) and monoamine oxidase (MAO) activity was studied during the summer in the active male ground squirrel (Citellus citellus) treated with metopirone, adrenocorticotrophin (ACTH), or dexamethasone. Cortisol and corticosterone almost disappeared from the circulation 1 hr after treatment with metopirone (75 mg/animal); they were also lower than in the controls 24 hr later (P < 0.025). Metopirone treatment resulted in a slight increase in adrenal weight as well as a decrease in adrenal PNMT activity (P < 0.01). In the liver, heart, kidney, lung, brown fat, and hypothalamus MAO activity was higher in metopirone-treated animals than in the controls (P < 0.01). Treatment with ACTH (6 IU of depot preparation/animal) resulted in an increase in adrenal weight (P < 0.01) as well as in PNMT activity (P < 0.005). In corticotrophin- as well as in dexamethasone (1 mg/animal)-treated animals MAO activity in the liver, heart, kidney, lung, brown fat, and hypothalamus was lower than in the nontreated controls (for all the tissues except the lung P < 0.005; for the lung P < 0.05). The results suggest that the adrenal cortex participates in the control of PNMT and MAO activity in the ground squirrel during the summer by stimulating PNMT activity and depressing MAO activity.