CORRELATION OF HYPOTHALAMIC LHRH, PITUITARY LH AND PLASMA LH IN DEVELOPING RATS

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 70  (2) , 131-141
Abstract
Hypothalamic LHRH [luteinizing hormone-releasing hormone], pituitary LH [luteinizing hormone] and plasma LH levels were measured in rats of both sexes from day 5-60 after birth. The hypothalamic LHRH content was very high in 1 wk old male and female rats. It declined gradually till day 17 in the female rat and sharply on day 10 in the male rat. Subsequently the hypothalamic LHRH content increased and showed peak values on day 25 in the female rat and on day 45 in the male rat. It decreased markedly at, puberty in both sexes (day 37 in the female rat and day 52-60 in the male rat). Apparently maturation of hypothalamo-hypophyseal-axis proceeds in 3 distinct stages. Observations on days 17, 25 and 37 in the female rat and on days 5, 7, 10 and 22 in the male rat show an inverse relationship between hypothalamic LHRH and plasma LH and a parallel relationship between pituitary and plasma LH. Marked decline in content of hypothalamic LHRH at puberty in both sexes indicates that release of threshold levels of LHRH from the hypothalamus may be the event initiating pubertal changes in rat.