Chitravanshi V C, Sapru H N
Section of Neurological Surgery, New Jersey Medical School, Newark 07103, USA.
Brain Res. 1996 Apr 9;715(1-2):104-12. doi: 10.1016/0006-8993(95)01565-5.
The neurotransmission of bulbospinal respiratory drive is believed to involve primarily non-NMDA receptors located in the phrenic motonucleus (PMN). This conclusion is based on studies carried out mainly on in vitro brainstem-spinal cord preparations of the neonatal rat. The present study was undertaken to investigate the transmitter/receptor mechanisms in the PMN which are involved in the neurotransmission of inspiratory drive, using an in vivo adult rat model. Microinjections of glutamate, NMDA and AMPA into the PMN elicited an increase in the phrenic nerve (PN) background discharge. These injections did not alter significantly the frequency of spontaneously occurring PN bursts confirming that mechanisms responsible for respiratory rhythm reside in the supraspinal structures. Microinjections of an NMDA receptor blocker (AP-7), in concentrations that did not alter the responses to a non-NMDA receptor agonist (AMPA), reduced the PN amplitude significantly. Similarly, microinjections of a potent non-NMDA receptor blocker (NBQX), in concentrations that did not alter responses to NMDA, reduced the PN amplitude significantly. Sequential microinjections, within an interval of 5 min, of AP-7 and NBQX into the PMN, resulted in a dramatic reduction in the spontaneous PN bursts. The reduction of PN amplitude started immediately after the microinjection of AP-7 and NBQX, either alone or in combination, and reached a maximum within 5-10 min. These results indicate that, unlike in the neonatal rat, both NMDA and non-NMDA receptors located in the PMN play a significant role in the neurotransmission of the inspiratory drive in the adult rat.
延髓脊髓呼吸驱动的神经传递被认为主要涉及位于膈运动核（PMN）的非NMDA受体。这一结论主要基于对新生大鼠体外脑干脊髓制剂进行的研究。本研究采用成年大鼠体内模型，旨在研究PMN中参与吸气驱动神经传递的递质/受体机制。向PMN微量注射谷氨酸、NMDA和AMPA可引起膈神经（PN）背景放电增加。这些注射并未显著改变自发PN爆发的频率，证实负责呼吸节律的机制存在于脊髓上结构中。以不改变对非NMDA受体激动剂（AMPA）反应的浓度微量注射NMDA受体阻滞剂（AP - 7），可显著降低PN幅度。同样，以不改变对NMDA反应的浓度微量注射强效非NMDA受体阻滞剂（NBQX），也可显著降低PN幅度。在5分钟的间隔内，向PMN依次微量注射AP - 7和NBQX，可导致自发PN爆发显著减少。单独或联合微量注射AP - 7和NBQX后，PN幅度立即开始降低，并在5 - 10分钟内达到最大值。这些结果表明，与新生大鼠不同，位于PMN的NMDA和非NMDA受体在成年大鼠吸气驱动的神经传递中均发挥重要作用。
