Byerley D J, Kiser T E, Bertrand J K, Kraeling R R
Animal and Dairy Science Department, University of Georgia, Athens 30602.
J Anim Sci. 1992 Sep;70(9):2794-800. doi: 10.2527/1992.7092794x.
This study was conducted to investigate regulation of LH release by opioid peptides during puberal development in beef heifers. Fourteen heifers were randomly assigned to receive naloxone (opioid antagonist) i.v. at dosages of either 1 mg.kg BW-1.wk-1 (Dose 1) or .25 mg.kg BW-1.wk-1 (Dose 2) for 13 wk or until puberty. Blood was sampled (one sample every 15 min) 6 h before (prenaloxone) and 2 h after naloxone administration. Two hours after naloxone administration, GnRH (10 ng/kg BW) was administered and blood was sampled for 1 h. Nine heifers attained puberty during the study. There were no differences between naloxone dosage groups for any measured variables. Therefore, heifers were grouped dependent on the attainment of puberty. Prenaloxone concentrations of serum LH and LH pulse frequency were normal for prepuberal heifers. Serum LH concentrations increased within 30 min after naloxone 135 of 139 times it was administered (P less than .05). Serum LH concentrations during the hour after naloxone were higher (P less than .05) than those during the hour before naloxone in both puberal and nonpuberal heifers. In puberal heifers, serum LH pulse height during the hour after naloxone was greater (P less than .02) at 5 wk before puberty and lower (P less than .02) the week before puberty than at other times during the trial. There was no effect of week on serum LH pulse height after naloxone in heifers that failed to attain puberty during the study. Response of LH to GnRH was similar between groups.(ABSTRACT TRUNCATED AT 250 WORDS)
本研究旨在调查在育肥牛小母牛青春期发育过程中阿片肽对促黄体生成素（LH）释放的调节作用。14头小母牛被随机分配，静脉注射纳洛酮（阿片类拮抗剂），剂量分别为1mg·kg体重-1·周-1（剂量1）或0.25mg·kg体重-1·周-1（剂量2），持续13周或直至青春期。在注射纳洛酮前6小时（注射前）和注射后2小时采集血液样本（每15分钟采集一次）。注射纳洛酮2小时后，注射促性腺激素释放激素（GnRH，10ng/kg体重），并采集血液样本1小时。研究期间有9头小母牛进入青春期。在任何测量变量方面，纳洛酮剂量组之间均无差异。因此，根据是否进入青春期对小母牛进行分组。青春期前小母牛注射前血清LH浓度和LH脉冲频率正常。注射纳洛酮后30分钟内，血清LH浓度升高（139次中有135次）（P<0.05）。在青春期和非青春期小母牛中，注射纳洛酮后1小时内的血清LH浓度均高于注射前1小时（P<0.05）。在青春期小母牛中，注射纳洛酮后1小时内的血清LH脉冲高度在青春期前5周时较大（P<0.02），而在青春期前一周时较低（P<0.02），与试验期间的其他时间相比。在研究期间未进入青春期的小母牛中，注射纳洛酮后周数对血清LH脉冲高度没有影响。各组之间LH对GnRH的反应相似。（摘要截断于250字）
