Abstract:

bstract:Objective
To observe the effects of the intrathecal injection of N-methyl-D-aspartate (NMDA) receptor agonist NMDA and antagonist MK801 on the cardiacsomatic motor reflex (CMR) induced by intrapericardial  bradykinin (BK), and explore the role of Glu receptor NMDA subunit in nociceptive information transmission of the heart in the spinal cord.
Methods 26 male SD rats were randomly divided into BK group(n=8), BK + NMDA group(n=6), BK + MK801 group(n=6), and BK + MK801 + NMDA group(n=6).CMR was induced by intrapericardial  BK, and the effects of intrathecal injection of drug in various groups on CMR were observed.The changes of CMR were monitored via electromyogram (EMG) responses of dorsal spinotrapezius muscle to intrapericardial  BK.Results There
 were no significant differences among EMG induced by intrapericardial  BK, four times at 40 min intervals.Compared with control, the EMG was increased from 100% of control to (149.86±8.54)% by intrathecal injection of NMDA, there was significant difference of EMG between before and after intrathecal injection of NMDA (P<0.05).However, the EMG was decreased from 100% of control to (96.22±2.31)% by intrathecal injection of MK801, there was  no statistically significant difference (P>0.05).The EMG was increased from 100% of control to (103.09±4.13)% by intrathecal combinative injection of MK801 and NMDA, there was no significant difference of EMG between before and after intrathecal combined injection of MK801 and NMDA (P>0.05).Conclusion CMR induced by intrapericardial  BK has reliable repeatability and the spinal cord level of NMDA receptor involves in the modulation of CMR.

Key words: bradykinin, cardiacsomatic motor reflex, N-methy1-D-aspartate, MK801