家兔脑内微量注射或脊髓珠网膜下腔注射氟安定的呼吸抑制作用

实验在49只局部麻醉、肌肉麻痹、切断双侧颈迷走神经的家兔上进行。观察到一侧孤束核(NTS)区微量注射氟安定,使对侧膈神经放电平均幅度减低,呼吸频率加快。事先在NTS区微量注射GABA 受体拮抗剂印防己毒素,可阻断氟安定的减低膈神经放电平均幅度的作用。在脑桥头端横断脑干出现长吸式呼吸的免上,一侧NTS区微量注射氟安定,也使对侧膈神经放电平均幅度减低,但呼吸频率减慢。在脑桥结合臂旁内侧核(NPBM)区微量注射氟安定,使呼吸频率明显减慢,吸气和呼气时程延长,这效应可被毒扁豆碱阻断。脊髓蛛网膜下腔注射氟安定,使膈神经放电平均幅度减低,血压下降,这效应可被印防己毒素阻断。结果提示,NPBM 的存在与呼吸频率加快有关;而氟安定作用于NPBM区,却减慢呼吸频率,其机制可能是抗胆碱能作用。氟安定直接作用于NTS 区或脊髓使膈神经放电平均幅度减低、血压下降,其机制可能与激活GABA 受体有关。

RESPIRATORY DEPRESSION FOLLOWING MICROINJECTION OR INTRATHECAL INJECTION OF FLURAZEPAM IN RABBITS

Experiments were performed on 49 locally anesthetized, paralyzed and vago-tomized rabbits. Unilateral microinjection of flurazepam in nucleus tractus so-litarius (NTS) depressed the average phrenic activity on the contralateral side,but increased the respiratory rate. Pretreatmeat of picrotoxin in the same regionprevented the depressant effect of flurazepam on average phrenic activity. Whilerespiration of the animal had been made apneustic by decerebration at pontinelevel, unilateral microinjection of flurazepam in NTS also caused a reduction ofaverage phrenic activity but prolongation of respiratory cycle. Microinjectedflurazepam in nucleus parabrachialis medialis (NPBM) decreased the respiratoryrate and lengthened inspiratory and expiratory duration. These effects were re-versed by microinjection of physostigmine in the same regon. Intrathecal injectedflurazepam decreased the average phrenic activity and lowered arterial bloodpressure. These effects were reversed by intrathecal injection of picrotoxin in thesame region. The results obtained indicated that NPBM might take part in theincrease of respiratory rate, but microinjected flurazepam in NPBM decreasedrespiratory rate by its anticholinergic action. The respiratory depressent actionof flurazepam in NTS or spinal cord might be GABA-mediated.