Effect of hypophysectomy on schedule-induced wheelrunning.

Previous research has shown that adrenalectomy suppresses schedule-induced wheelrunning, and that the suppressant effect of adrenalectomy can be totally reversed by the replacement of corticosterone. The present study confirms the role of the hormones of the pituitary adrenocortical axis in the control of schedule-induced wheelrunning by means of hypophysectomy. As anticipated, hypophysectomy also suppressed schedule-induced wheelrunning. The suppressant effect of hypophysectomy on schedule-induced wheelrunning was partially, but significantly restored by the implantation of corticosterone. Present findings, in conjunction with the previous work, show that schedule-induced wheelrunning is markedly dependent on the function of the pituitary-adrenal axis, and the nature of pituitary-adrenal involvement is mainly through circulating corticosterone levels.