Journal article

MORPHINE DECREASES LH-SECRETION IN OVARIECTOMIZED EWES ONLY AFTER STEROID PRIMING AND NOT BY DIRECT PITUITARY ACTION

RJE HORTON, JY LI, JT CUMMINS, AI SMITH, PJ SHEN, IJ CLARKE

NEUROENDOCRINOLOGY | KARGER | Published : 1990

Abstract

To determine whether opiates directly modulate pituitary LH secretion in vivo, morphine was administered to hypothalamo-pituitary-disconnected (HPD) ewes which were receiving exogenous pulses of GnRH. To define the steroidal background which is permissive to a morphine-induced decrease in LH secretion, ovariectomized (OVX) ewes were treated as follows in groups of four: group 1, no implant; group 2, small 17 beta-estradiol (E2) (1 cm long x 0.33 diameter) and progesterone (P) implants; group 3, medium E2 (1 cm long x 0.46 diameter) and P implants, and group 4, medium E2 implants. Jugular blood samples were taken at 10-min intervals for 9 h, during which there was a 3-hour pretreatment period..

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