Joseph S A, McMillen I C, Walker D W
J Appl Physiol (1985). 1987 Feb;62(2):673-8. doi: 10.1152/jappl.1987.62.2.673.
To determine whether endogenous opioids influence the fetal breathing response to CO2 we have investigated the effect of the opiate antagonist, naloxone on the incidence, rate, and amplitude of breathing movements during hypercapnia in fetal lambs in utero. In 20 experiments in six pregnant sheep (130-145 days gestation) hypercapnia was induced by giving the ewe 4-6% CO2-18% O2 in N2 to breathe for 60 min. After 30 min of hypercapnia either naloxone (13 experiments) or saline (7 experiments) was infused intravenously for the remaining 30 min. During hypercapnia breath amplitude increased from 5.8 +/- 0.5 to 9.1 +/- 1.2 mmHg (P less than 0.001), and infusion of naloxone was associated with a further significant increase to 15.7 +/- 1.2 mmHg (P less than 0.001). Naloxone had no effect on the incidence or rate of breathing movements during hypercapnia. After hypercapnia there was a significant decrease in the incidence of fetal breathing movements in the naloxone group (14.7 +/- 3.2%). Infusion of saline during hypercapnia had no effect on incidence, rate, or amplitude of fetal breathing movements. These results suggest that endogenous opioids act to suppress or limit breath amplitude during hypercapnia but do not affect rate or incidence of breathing movements.
为了确定内源性阿片类物质是否影响胎儿对二氧化碳的呼吸反应，我们研究了阿片类拮抗剂纳洛酮对子宫内胎羊高碳酸血症期间呼吸运动的发生率、频率和幅度的影响。在对6只怀孕绵羊（妊娠130 - 145天）进行的20次实验中，通过让母羊吸入4 - 6%二氧化碳 - 18%氧气的氮气混合气60分钟来诱导高碳酸血症。高碳酸血症30分钟后，在剩余的30分钟内静脉注射纳洛酮（13次实验）或生理盐水（7次实验）。在高碳酸血症期间，呼吸幅度从5.8±0.5 mmHg增加到9.1±1.2 mmHg（P<0.001），注射纳洛酮后呼吸幅度进一步显著增加至15.7±1.2 mmHg（P<0.001）。纳洛酮对高碳酸血症期间呼吸运动的发生率或频率没有影响。高碳酸血症后，纳洛酮组胎儿呼吸运动的发生率显著降低（14.7±3.2%）。高碳酸血症期间注射生理盐水对胎儿呼吸运动的发生率、频率或幅度没有影响。这些结果表明，内源性阿片类物质在高碳酸血症期间起到抑制或限制呼吸幅度的作用，但不影响呼吸运动的频率或发生率。
