Bairam A, Marchal F, Crance J P, Vert P, Lahiri S
Laboratoire de Physiologie, Faculté de Médecine, INSERM U. 272, Université de Nancy, Vandoeuvre-lès-Nancy, France.
Biol Neonate. 1993;64(1):26-35. doi: 10.1159/000243967.
Doxapram is a respiratory stimulant which acts on peripheral chemoreceptors and central respiratory neurons in a dose-dependent fashion in the adult cat. In the newborn, the mechanisms of action of doxapram are still unclear. To evaluate the effects of doxapram on the carotid chemosensory discharge and its relationship with dopaminergic mechanisms in the carotid body, two groups of kittens less than 13 days old, anesthetized, artificially ventilated and paralyzed, were prepared for the recording of a single or a few chemosensory afferents of the carotid sinus nerve. The chemosensory activity was recorded under five conditions of inspired gas mixtures (21 and 8% O2 in N2, 100% O2, 5 and 10% CO2 in O2). Group 1 (n = 9) received only doxapram and group 2 (n = 8) was pretreated with haloperidol (1 mg/kg), a dopamine D2-receptor blocker, before receiving doxapram. Doxapram significantly stimulated the discharge rate of the carotid chemoafferents under all conditions of inspired gas. The chemosensory discharge was increased by haloperidol, and was raised further after doxapram by an amount similar to group 1. For instance, in normoxia, the activity increased from 2.9 +/- 0.4 to 7.5 +/- 0.9 impulse/s (mean +/- SEM, p < 0.01) in group 1 and from 3.8 +/- 0.6 to 9.1 +/- 1.0 impulse/s (p < 0.01) in group 2. These results indicate that the mechanisms of response of carotid chemoreceptor to doxapram are developed in the newborn kitten and doxapram acts independent of the dopaminergic mechanisms in the carotid body.
多沙普仑是一种呼吸兴奋剂，在成年猫中，它以剂量依赖的方式作用于外周化学感受器和中枢呼吸神经元。在新生儿中，多沙普仑的作用机制仍不清楚。为了评估多沙普仑对颈动脉化学感受性放电的影响及其与颈动脉体中多巴胺能机制的关系，制备了两组小于13日龄的小猫，对其进行麻醉、人工通气和麻痹，以记录颈动脉窦神经的单个或少数化学感受传入纤维。在五种吸入气体混合物条件下（氮气中21%和8%的氧气、100%的氧气、氧气中5%和10%的二氧化碳）记录化学感受活动。第一组（n = 9）仅接受多沙普仑，第二组（n = 8）在接受多沙普仑之前先用氟哌啶醇（1 mg/kg）进行预处理，氟哌啶醇是一种多巴胺D2受体阻滞剂。在所有吸入气体条件下，多沙普仑均显著刺激颈动脉化学感受传入纤维的放电率。氟哌啶醇可增加化学感受性放电，在给予多沙普仑后，放电率进一步升高，升高幅度与第一组相似。例如，在常氧条件下，第一组的活动从2.9±0.4增加到7.5±0.9脉冲/秒（平均值±标准误，p < 0.01），第二组从3.8±0.6增加到9.1±1.0脉冲/秒（p < 0.01）。这些结果表明，新生小猫的颈动脉化学感受器对多沙普仑的反应机制已经发育，且多沙普仑的作用独立于颈动脉体中的多巴胺能机制。
