Lewis A B, Ferry D A, Sadeghi M
Biol Neonate. 1986;50(5):278-87. doi: 10.1159/000242610.
Endogenous opiates have been shown to alter cardiopulmonary activity in a variety of animal models. The present investigation in fetal sheep evaluate the response of heart rate, blood pressure and breathing movements (FBM) to central nervous and intravenous meth-enkephalin and beta-endorphin. Marked bradycardia was noted within 3-5 s of intravenous meth-enkephalin administration and lasted less than 10-15 s. An 84.8 +/- 19.0% prolongation in cardiac cycle length was observed after 20 nmol/kg meth-enkephalin (p less than 0.02). In contrast, there was no significant change in heart rate following 2-50 nmol/kg beta-endorphin. The meth-enkephalin-induced slowing of heart rate was virtually eliminated by autonomic blockade with atropine or hexamethonium but merely partially blunted by naloxone. FBM were not altered by intravenous administration of either opiate. However, both meth-enkephalin and beta-endorphin produced a dramatic increase in FBM following injection into the cisterna magna. Prior to opioid administration, FBM were noted 11 +/- 1.4% of the time. Intracisternal opiates resulted in a 43.9 +/- 10.1% incidence of FBM for up to 60 min. Parasympathetic blockade with atropine had no effect on the pattern of FBM following intracisternal opiate administration whereas naloxone terminated the increased respiratory activity within 1 min. These data suggest a potential role for endogenous opiates in the modulation of fetal cardiorespiratory function.
内源性阿片类物质已被证明可在多种动物模型中改变心肺活动。本对胎羊的研究评估了心率、血压和呼吸运动（FBM）对中枢神经系统及静脉注射甲硫氨酸脑啡肽和β-内啡肽的反应。静脉注射甲硫氨酸脑啡肽后3 - 5秒内出现明显心动过缓，持续时间不到10 - 15秒。给予20 nmol/kg甲硫氨酸脑啡肽后，心动周期长度延长了84.8±19.0%（p<0.02）。相比之下，给予2 - 50 nmol/kgβ-内啡肽后心率无显著变化。用阿托品或六甲铵进行自主神经阻滞可几乎消除甲硫氨酸脑啡肽诱导的心率减慢，但纳洛酮仅能部分减弱该效应。静脉注射任何一种阿片类药物均未改变FBM。然而，甲硫氨酸脑啡肽和β-内啡肽注入小脑延髓池后均使FBM显著增加。在给予阿片类药物之前，FBM出现的时间占11±1.4%。脑池内注入阿片类药物导致FBM发生率在长达60分钟内为43.9±10.1%。用阿托品进行副交感神经阻滞对脑池内注入阿片类药物后的FBM模式无影响，而纳洛酮在1分钟内终止了增加的呼吸活动。这些数据表明内源性阿片类物质在调节胎儿心肺功能方面可能发挥作用。
