02187naa a2200361 a 450000100080000000500110000800800410001902400270006010000120008724501410009926000090024052012020024965000220145165000150147365000120148865000100150065000350151065000170154565000240156265000170158665000150160365000170161865000120163565000190164765000140166665000170168065300170169765300090171465300140172370000150173770000130175277300600176515228802023-06-01       1993    bl uuuu     u00u1 u    #d7 a10.1159/0001264182DOI1 aITO, K.  aOpioid peptidergic control of gonadotropin-releasing hormone pulse generator activity in the ovariectomized goat.h[electronic resource]  c1993  aAbstract: The role of endogenous opioid peptides in the control of gonadotropin-releasing hormone pulse generator activity was examined in long-term ovariectomized goats by recording the hypothalamic multiple-unit activity specifically associated with pulsatile luteinizing hormone secretion (MUA volleys). Administration of naloxone, an opioid receptor antagonist, at a rate of 1.0 mg/kg/h for 2 h resulted in shorter (p &lt 0.05) intervals between MUA volleys than during the control period (61.6 +/- 0.7 vs. 92.5 +/- 7.2 min) in animals treated with progesterone and estradiol that had reproduced a steroidal milieu during the luteal phase. Similarly, in the absence of steroidal treatment, the interval between MUA volleys was shortened (p &lt 0.01) in a dose-dependent manner from 42.3 +/- 3.7 min (control) to 35.1 +/- 3.9, 32.6 +/- 4.1, and 27.0 +/- 1.7 min when infused with 0.2, 1.0, and 5.0 mg/kg/h of naloxone, respectively. On the other hand, the duration of each MUA volley was lengthened by naloxone. The results indicate that the hypothalamic gonadotropin-releasing hormone pulse generator activity is under a tonic suppression by endogenous opioid peptides in ovariectomized goats.  aElectrophysiology  aEndorphins  aFemales  aGoats  aGonadotropin-releasing hormone  aHypothalamus  aLuteinizing hormone  aPharmacology  aPhysiology  aProgesterone  aCaprino  aEndocrinologia  aEstradiol  aReprodução  aDrug effects  aGnRH  aPeptideos1 aTANAKA, T.1 aMORI, Y.  tNeuroendocrinologygv. 57, n. 4, p. 634-639, Apr. 1993.