安定对家兔呼吸的作用

在切断迷走神经和局部麻醉的家兔中观察了静脉注射安定(2mg/kg)对呼吸和循环的影响。在动物进行自然呼吸的条件下,安定使每分通气量减少,心率变慢和血压降低。在将动物肌肉麻痹并进行正压人工呼吸的条件下,安定使呼吸频率加快,吸气时程和呼气时程缩短,即呼吸周期缩短。此外,膈神经放电的高频振荡频率增高而电位的幅度变小,动物的血压也降低。在桥脑头端去大脑而表现长吸式呼吸,以及在延體髓纹水平横断脑干而表观喘息式呼吸的动物中,安定亦使膈神经放电的幅度减小,呼吸周期延长和血压降低。以上结果表明安定可使呼吸抑制、血压降低,而其作用的基本部位可能主要在延髓。

RESPIRATORY RESPONSE OF DIAZEPAM IN THE RABBIT

Experiments were carried out on bilaterally vagotomized rabbits under local anaesthesia.The effects ofdiazepam(2 mg/kg,i.v.)on respiration and cardiovas-cular activity were investigated.In the first group of animals which breathednaturally,intravenous administration of diazepam resulted in a reduction in respi-ratory minute volume,decrease in heart rate and arterial blood pressure.Inthe second group,experiments were performed on immobilized rabbits underpositive pressure artificial ventilation.Diazepam caused decreases in both theinspiratory and expiratory durations,thus shortening the respiratory cycle.Mean-while,the oscillatory frequency of high frequency oscillation(HFO)was increased,the amplitude of the phrenic nerve discharge was decreased,and the arterialblood pressure was also lowered.In the third group,when respiration of theanimals had been made either apneustic by decerebration at pontine level orgasping by transection at the medullary striae,diazepam also caused a reduction inthe amplitud f the phrenic nerve discharges,prolongation of the respiratorycycle and lowering of blood pressure.The results obtained indicate that diazepaminhibits the respiratory activity and lowers blood pressure.These effects are pos-sibly mediated mainly by the medulla oblongata.