Barb C R, Kraeling R R, Rampacek G B, Whisnant C S
Biol Reprod. 1986 Sep;35(2):368-71. doi: 10.1095/biolreprod35.2.368.
Twelve lactating sows were used at 22.4 +/- 0.8 days postpartum to determine whether endogenous opioid peptides (EOP) are involved in the suckling-induced inhibition of luteinizing hormone (LH) secretion. Four sows each received either 1, 2, or 4 mg/kg body weight of naloxone (NAL), an opiate antagonist, in saline i.v. Blood was collected at 15-min intervals for 2 h before and 4 h after NAL treatment. All sows were then given 100 micrograms gonadotropin-releasing hormone (GnRH) in saline i.v., and blood samples were collected for an additional h. Pigs were weaned after blood sampling. At 40 h after weaning, sows were treated and blood samples collected as during suckling. Serum concentrations of LH after treatment with NAL were similar for all doses; therefore, the data were pooled across doses. During suckling, serum concentrations of LH were 0.41 +/- 0.04 ng/ml before NAL treatment, increased to 0.65 +/- 0.08 ng/ml at 30 min after NAL treatment, and remained elevated above pretreatment concentrations for 120 min (p less than 0.05). Naloxone failed to alter serum concentrations of LH after weaning. These data indicate that EOP may be involved in the suckling-induced suppression of LH secretion and that weaning may either decrease opioid inhibition of LH secretion or decrease pituitary LH responsiveness to endogenous GnRH released by NAL.
选用12头产后22.4±0.8天的泌乳母猪，以确定内源性阿片肽（EOP）是否参与哺乳诱导的促黄体生成素（LH）分泌抑制。每组4头母猪，分别静脉注射生理盐水溶解的1、2或4mg/kg体重的阿片拮抗剂纳洛酮（NAL）。在NAL处理前2小时和处理后4小时，每隔15分钟采集一次血液。然后，给所有母猪静脉注射生理盐水溶解的100微克促性腺激素释放激素（GnRH），并额外采集1小时血样。采血后对仔猪进行断奶。断奶40小时后，按照哺乳期间的处理方式对母猪进行处理并采集血样。所有剂量的NAL处理后，LH的血清浓度相似；因此，将各剂量的数据合并。哺乳期间，NAL处理前LH的血清浓度为0.41±0.04ng/ml，NAL处理后30分钟升至0.65±0.08ng/ml，并在120分钟内一直高于处理前浓度（p<0.05）。纳洛酮未能改变断奶后LH的血清浓度。这些数据表明，EOP可能参与哺乳诱导的LH分泌抑制，断奶可能会降低阿片类物质对LH分泌的抑制作用，或者降低垂体对NAL释放的内源性GnRH的LH反应性。
