Abstract:

To study the descending inhibitory effect of the lateral reticular nucleus (LRN) treated with electrical stimulation on the cardiosomatic motor reflex (CMR) induced by intrapericardial capsaicin (IC) in rats and its mechanism.Methods  22 male SD rats were randomly divided into electrical stimulation group(n=7),electrical stimulation plus 3 g?L-1 yohimbine group(n=5),electrical stimulation plus 5 g.L^-1 yohimbine  group(n=5) and electrical stimulation plus vehicle group(n=5).The  electromyogram (EMG)  changes  of dorsal spinotrapezius muscle of CMR induced by  IC of rats were observed following intervention with treatment factors in various groups.Results Compared with control group,EMG could be inhibited by electrical stimulation of 10,20 and 30  μA in  LRN,the inhibitory effect was increased with the increasing of  the electrical stimulation intensity accompanied or not accompanied with changes of blood pressure;the EMG reduced to 51.41%,21.11% and 1.43%  of the control(P<0.001);Compared with electrical stimulation(10  μA) group,intrathecal injection of adrenergic α2 receptor antagonist yohimbine (3 and 5 g.L^-1) reversed the inhibitory effects of LRN stimulation on CMR,the  EMG responses increased from 41.34% to 72.40% and 78.73%,respectively (P<0.01).Conclusion Electrical stimulation of LRN can produce descending inhibition on CMR and  α2-adrenoceptors at spinal cord level may be involved in the inhibition.

Key words: lateral reticular nucleus;cardiosomatic motor reflex;descending inhibition;yohimbine