反射性呼吸暂停中延髓各类呼吸性神经元的放电变化

在向家兔颈动脉窦区注入拘椽酸钠引起呼吸暂停期间,和在持续性肺充气引起延长的呼气相中,延髓大多数吸气神经元和膈神经停止放电;而大多数呼气性神经元呈连续性放电,放电频率持续地高于或接近于平静呼气时呼气神经元的高峰放电频率,并伴随肋间内肌电活动增强,直至呼气性神经元放电频率衰减或停止放电时,膈神经才恢复放电。这提示呼气性神经元的持续兴奋状态可能与呼气性呼吸暂停的维持或呼气相的延长有关。在延髓闩前部可以记录到少数放电频率渐增型的跨时相呼气-吸气神经元,在呼吸暂停期间,它们呈低频连续放电,逐渐增大放电频率,在其放电频率急剧增高时,膈神经恢复放电。这提示该类神经元可能与吸气的发动有关。本文尚就呼吸节律的发生机制做了讨论。

DISCHARGE CHANGES OF VARIOUS MEDULLARY RESPIRATORY NEURONS DURING REFLEXIVE APNEA

Most medullary inspiratory neurons and phrenic nerve ceased firing, whilethe majority of expiratory neurons fired continuously during the period of apneainduced by intracarotid sinus injection of sodium citrate and during the lengthenedexpiratory phase caused by sustaining lung inflation. Furthermore, the dischargefrequencies of most expiratory neurons were continuously higher than or near totheir normal peak frequencies, and in the mean time, the electrical activities ofinternal intercostal muscles increased. The phrenic discharges did not recoveruntil the discharges of the expiratory neurons declined or ceased. The resultssuggest that the maintenance of expiratory apnea or lengthened expiratory phasemay be in relation to sustaining excitation of expiratory neurons. Several expiratory-inspiratory (EI) neurons with an augmenting frequency pattern were recordedin front of the obex. During apnea, these EI neurons fired continuously at a lowerfrequency and increased their firing rates progressively. The phrenic nerve restoredto fire just at the point when the EI neurons increased their firing rates abruptly.These results indicate that the EI neurons may be responsible for the start of inspira-tion. In addition, the mechanism of genesis of respiratory rhythm was discussed.