抄録
Spontaneous augmented breaths (SABs) occur sporadically during normal breathing and increase the episodes (fSAB) in hypoxia. We examined the effects of MK-801, a N-methyl-D-aspartate (NMDA) antagonist, on the SABs in unanesthetized rats in normoxia and hypoxia. The rat, which had been implanted diaphragm electromyogram (EMGdia) electrodes, was measured ventilation (by the barometric technique) and the SABs (by EMGdia) before and after an intravenous MK-801 injection (3 mg/kg), in normoxia and hypoxia (12%O2). MK-801 increased respiratory frequency (fR) of normal breathing due to a shortened expiratory time (TE) in normoxia, but decreased the fR due to a prolonged inspiratory time (TI) in hypoxia. On the SABs, by MK-801 injection, although inspiratory and expiratory phases in each SAB were modified as seen in normal breathing, the fSAB was not modified as seen in the fR in both gaseous conditions. In conclusion, NMDA receptor-mediated processes may determine cycle timing for individual normal breath and SAB, but may not crucial for determining the fSAB in unanesthetized rats. [Jpn J Physiol 55 Suppl:S108 (2005)]
