SECRETION OF GROWTH-HORMONE ELICITED BY INTRAVENOUS DESIPRAMINE IN THE CONSCIOUS, UNRESTRAINED RAT

1 Acute intravenous administration of either clonidine (Clon) (50-mu-g kg-1) or desipramine (DMI) (5 mg kg-1) elicited a pulse of growth hormone (GH) and corticosterone secretion in conscious, unrestrained rats. 2 The responses to DMI were similar to those with Clon, except that the GH pulse following DMI was delayed and was not dose-dependent. 3 The GH response to DMI was inhibited by prior administration of idazoxan (1 mg kg-1) or yohimbine (0.5 mg kg-1), but not by atropine (10-mu-g kg-1), sulpiride (5 mg kg-1) or prazosin (1 mg kg-1). 4 The corticosterone secretion following DMI was not altered by prior atropine, sulpiride or prazosin, but was augmented by idazoxan (1 mg kg-1). 5 GH secretion was not influenced by atropine, sulpiride, prazosin or idazoxan given alone. Idazoxan or yohimbine given alone elicited significant secretion of corticosterone. 6 It is concluded that i.v. DMI caused an activation through indirect mechanisms of alpha-2-adrenoceptors specifically involved in hypothalamic-pituitary regulation of GH release and also a distinct, independent and transient generalized activation of the pituitary-adrenal axis.