Abstract: Objective To investigate the role of neurokinin-1 (NK1) receptor and non-N-methyl-D-aspartate (non-NMDA)
receptor in modulating the cardiosomatic reflex in the spinal cord of rat. Methods The effects of intrathecal injection of NK1
receptor agonist Sar-SP and antagonist CP-96345 and non-NMDA receptor agonist NMDA and antagonist 6, 7-dinitro-1,
4-dihydro-quinoxaline-2,3-dione (DNQX) on the cardiosomatic reflex were observed in rats. The changes of the cardiosomatic
reflex were monitored by observing the electromyogram (EMG) responses of the dorsal spinotrapezius muscle to
intrapericardial bradykinin (BK) injection. Results Intrathecal injection of Sar-SP significantly facilitated EMG responses to
intrapericardial BK injection (P<0.05), which was completely blocked by intrathecal injection of NK1 antagonist CP-96345.
Similarly, intrathecal injection of NMDA obviously facilitated the EMG responses (P<0.05), which was partially reversed by
intrathecal injection of non-NMDA receptor antagonist DNQX. Intrathecal injection of Sar-SP along with NMDA significantly
increased EMG as compared with single administration of Sar-SP or NMDA (P<0.05). Conclusion The spinal cord levels of
NK1 receptor and non-NMDA receptor are involved in the modulation of the cardiosomatic reflex in rats.