CONTROL OF LUTEINIZING HORMONE RELEASE IN PREPUBERTAL FEMALE RATS: EVIDENCE FOR AN ENHANCED ABILITY OF THE HYPOTHALAMUS TO RELEASE LUTEINIZING HORMONE RELEASING HORMONE AS THE PITUITARY RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING HORMONE DECLINES

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Abstract
Department of Physiology, University of Texas Health Science Center at Dallas, Southwestern Medical School, Dallas, Texas 75235, U.S.A. (Received 5 January 1978) The concentrations of gonadotrophins in the plasma of the female rat are raised during the first 2 weeks of life, but thereafter decline to low values before puberty (Ojeda, 1976). The decrease is related, in part, to a diminished pituitary reponsiveness to luteinizing hormone releasing hormone (LH-RH; Ojeda, 1976). In contrast, the capability of the hypothalamic-pituitary unit to release luteinizing hormone (LH) in response to oestrogen injected s.c. increases during the same period (Caligaris, Astrada & Taleisnik, 1972). These findings and the observation that the gonadotrophic response of the hypothalamus to electrical stimulation also becomes more pronounced with age (Meijs-Roelofs, 1972) suggest that the capability of the prepubertal hypothalamus to release LH-RH increases concomitantly with a decline in pituitary responsiveness to the neurohormone. To test this hypothesis, the

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