Role of hypothalamic catecholamines in the regulation of luteinizing hormone and prolactin secretion in the ewe during seasonal anestrus

Neuroendocrinology
J C ThiéryJ P Ravault

Abstract

Separate studies with ewes have shown that catecholamines play an inhibitory role in the control of LH secretion during anestrus, and that there are structures in the lateral retrochiasmatic area (L-RCh), which could be involved in the regulation of gonadotrophin secretion. These observations have led to the hypothesis that the catecholaminergic structures in the L-RCh mediate the inhibition of pulsatile LH secretion by estradiol in the anestrous ewe. We tested this hypothesis by injecting 6-hydroxydopamine (6OH-DA) into the L-RCh of ovariectomized ewes during the anestrous season, and comparing the secretion of LH and prolactin in these animals with that in sham (injected with vehicle) and control (no injection) animals, in the presence and absence of exogenous estradiol. Finally, the effectiveness of the toxin was assessed by immunocytochemical techniques. When the ewes were treated with estradiol, LH pulse frequency was significantly lower in the controls (mean 1.1 pulses/4 h) and shams (0 pulses/4 h) than in the ewes treated with 6OH-DA (3.1 pulses/4 h). When the estradiol implants were removed, the frequencies increased to 5.1 pulses/4 h for the controls and 5.7 pulses/4 h in the ewes treated with 6OH-DA. These were not si...Continue Reading

Citations

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