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Concentrations of immuno reactive lhrh discrete brain regions of the cockerel effects of castration and testosterone replacement therapy






Journal of Endocrinology 96(3): 471-480

Concentrations of immuno reactive lhrh discrete brain regions of the cockerel effects of castration and testosterone replacement therapy

The validity of using a radioimmunoassay employing an antiserum raised against synthetic LHRH for the quantification of LHRH in birds was investigated. Extracts of avian hypothalamus yielded displacement curves which were parallel to that of the synthetic LHRH standard and the immunoreactive potencies of a number of extracts assayed concurrently using 2 different anti-LHRH sera were similar. Moreover, after chromatography of cockerel hypothalamic extract on carboxymethyl-cellulose, immunoreactive and biologically active LHRH were found in the same eluate fractions. Immunoreactive LHRH was widely distributed in cockerel hypothalamus with the highest concentrations present in the mediobasal hypothalamus (MBH; 6.55 .+-. 1.86 pg/.mu.g protein, n = 6) and medial preoptic region (POR; 0.95 .+-. 0.07 pg/.mu.g protein, n = 6). The postcastration rise in plasma LH [lutropin] in the cockerel was accompanied by significant (P < 0.05) increases in the concentration of LHRH in 5 hypothalamic areas including the POR; testosterone replacement therapy completely reversed these effects. Although castration raised the mean concentration of LHRH in 4 other hypothalamic areas including the MBH, these differences were not significant. However, testosterone replacement therapy depressed LHRH in all 4 regions to levels significantly (P < 0.05) less than those in castrated cockerels. The negative feedback action of testosterone on LH secretion in the cockerel evidently is mediated, at least in part, by an action on hypothalamic LHRH-producing neurons.

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Accession: 005029931



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