Blockade of the Release of Gonadotropins and Prolactin by Subcutaneous or Intraventricular Injection of Atropine in Male and Female Rats1

Abstract

To determine whether cholinergic pathways are involved in central nervous system (CNS) control of gonadotropin and prolactin release, atropine sulfate was injected sc (70 mg/100 g body wt) or directly into the third ventricle (250 μg) in order to block cholinergic receptors. The alkaloid injected by either route at 11:45–1:15 on the day of proestrus blocked the surges of LH, FSH and prolactin during the afternoon. Following orchidextomy, sc atropine prevented the elevation of plasma FSH and LH that normally occurred 16 and 24 hr post—castration. When atropine was injected into the third ventricle 24 hr post—orchidectomy, plasma LH decreased significantly within 2 hr. At 3–5 weeks post—ovariectomy or orchidectomy, sc injection of the alkaloid decreased plasma LH within 1 hr in females but the decrease was only apparent after 24 hr in the castrate males. Since injection of synthetic LHreleasing factor (LRF) elevated plasma LH in both proestrous females and castrate males injected sc with atropine, the action of atropine is thought to be on the CNS, and it is postulated that cholinergic pathways are implicated in the CNS control of gonadotropin and prolactin secretion by the adenohypophysis.(Endocrinology92: 1714, 1973)