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Titolo:
ENDOGENOUS OPIOID-PEPTIDES CONTROL THE AMPLITUDE AND SHAPE OF GONADOTROPIN-RELEASING-HORMONE PULSES IN THE EWE
Autore:
GOODMAN RL; PARFITT DB; EVANS NP; DAHL GE; KARSCH FJ;
Indirizzi:
W VIRGINIA UNIV,HLTH SCI CTR,DEPT PHYSIOL,POB 9229 MORGANTOWN WV 26506 UNIV MICHIGAN,REPROD SCI PROGRAM ANN ARBOR MI 48109
Titolo Testata:
Endocrinology
fascicolo: 6, volume: 136, anno: 1995,
pagine: 2412 - 2420
SICI:
0013-7227(1995)136:6<2412:EOCTAA>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
LUTEINIZING-HORMONE; LH-SECRETION; BETA-ENDORPHIN; ESTROUS-CYCLE; ELECTRICAL-ACTIVITY; RHESUS-MONKEY; PULSATILE SECRETION; MEDIAN-EMINENCE; MENSTRUAL-CYCLE; MATURE EWES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
50
Recensione:
Indirizzi per estratti:
Citazione:
R.L. Goodman et al., "ENDOGENOUS OPIOID-PEPTIDES CONTROL THE AMPLITUDE AND SHAPE OF GONADOTROPIN-RELEASING-HORMONE PULSES IN THE EWE", Endocrinology, 136(6), 1995, pp. 2412-2420

Abstract

This study was designed to test the hypothesis that endogenous opioidpeptides (EOP) mediate the negative feedback action of estradiol on GnRH pulse size in breeding season ewes. If this hypothesis is correct,one would predict that an EOP antagonist should increase GnRH pulse size in estradiol-treated ovariectomized (OVX+E), but not in OVX, ewes. We, therefore, examined the effects of naloxone on GnRH pulse profiles in the hypophyseal portal blood of OVX and OVX+E ewes (n = 6/group). Samples were collected every 10 min for 6 h before, 6 h during, and 4h after naloxone infusion. Estradiol treatment decreased GnRH pulse size and increased GnRH pulse frequency. Naloxone treatment had no effect on GnRH pulse frequency, but significantly increased GnRH pulse size. However, this stimulatory action of naloxone on GnRH pulse size wasevident in both OVX and OVX+E ewes. These results are thus not consistent with the hypothesis that EOP mediate the negative feedback actionof estradiol. Interestingly, naloxone not only increased GnRH pulse amplitude, but also prolonged the duration of GnRH release during a pulse. To obtain a more precise characterization of the effects of naloxone on the dynamics of GnRH release, pulse profiles in six OVX ewes were examined in hypophyseal portal blood sampled every minute for 4 h before and 4 h during naloxone infusion. Naloxone again increased both the amplitude and duration of GnRH pulses. The increase in GnRH pulse duration was caused by a prolongation of both the plateau and decliningphases of the GnRH pulse. In addition to these effects on GnRH release during a pulse, naloxone increased the amount of GnRH collected between pulses in both experiments. The stimulatory effects of naloxone onGnRH release in OVX ewes indicate that the role of EOP in the controlof GnRH is not limited to mediating the feedback actions of steroids. In particular, the dramatic effects of naloxone on GnRH pulse shape and interpulse GnRH levels raise the possibility that EOP play an important role in synchronizing the activity of the GnRH neurons involved in episodic GnRH secretion.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 26/11/20 alle ore 13:46:56