ACTIVATION OF THE ADENOHYPOPHYSIS BY INTRAVENOUS INJECTIONS OF EPINEPHRINE IN THE ATROPINIZED RABBIT

Abstract

introduction

Markee, Sawyer and Hollinshead (1948) stimulated the release of luteinizing hormone (or total gonadotrophin) from the rabbit hypophysis by the intrahypophyseal injection of small amounts of epinephrine (Adrenalin). After receiving 4 injections of 0.05 ml. epinephrine 1 mg./ml.), 5 out of 10 rabbits ovulated. However, intravenous and intracarotid injections of much higher dosages, up to the MLD, led to completely negative results (op. cit., and Marshall and Verney, 1936). These findings suggested that a discrete adrenergic mechanism, localized in the region of the hypophysis, might control pituitary activation. The presence of such an adrenergic mechanism in the reflex by which coitus stimulates LH release in the rabbit was affirmed by blocking copulation-induced ovulation with the adrenergic blocking agent Dibenamine (Sawyer, Markee and Hollinshead, 1947). Subsequent work revealed that the pituitary activation reflex also contains an atropine-blocked component which apparently precedes the Dibenamine-blocked mechanism (Sawyer, Markee and Townsend, 1949).