Abstract:

Objective To observe the regulation effect of spinal cord stimulation (SCS) on the cardiac nociception of the rats induced by bradykinin (BK), and to explore its mechanism. Methods 42 male healthy SD rats were randomly divided into electrophysiological experiment part (N=17) and immunohistochemistry part (N=25).All the rats were implemented cardiac catheterization to evoke heart pain.In electrophysiological experiment part,the rats were divided into BK reproducibility group (n=5) and BK+SCS group (n=12),and the electromyogram (EMG) percentage changes of dorsal spinotrapezius muscle evoked by BK were used as study indexes to examine the descending modulation of SCS on the cardiac nociception.In immunohistochemistry part,the rats were divided into control group (n=3),saline group (n=4),SCS group (n=6),BK group (n=6) and BK+SCS group (n=6).The expression level of c-fos in T3-T5 spinal dorsal horn was used as nociceptive evaluation to assess the protective effect of SCS on the cardiac nociception. Results Compared with BK reproducibility group,the EMG percentage in BK+SCS group was decreased (P<0.05),and the EMG declined to (54.02±4.95)% of control at 5 min after SCS (P<0.05);at 55 min after SCS,the EMG recovered to (74.82±4.74)% of control (P<0.05) and 105 min later,the EMG recovered to control level. Moreover,compared with control group (15.00±2.87),the expression levels of c-fos in saline control group (22.50±1.85) and SCS group (35.00±3.77) had no significant differences (P>0.05). The expression levels of c-fos in BK group (115.67±10.05) in T3-T5 spinal cord dorsal horn was higher than that in control group (P<0.05), and the expression level of c-fos (59.83±5.76) in BK+SCS group was significantly lower than that in BK group (P<0.05). Conclusion SCS can significantly inhibit the EMG and c-fos expression level induced by BK,which may be attributed to that SCS activates the spinal inhibitory interneurons and these inhibitory interneurons suppress the activities of cardiac pain sensitive neurons.

Key words: spinal cord stimulation, cardiac nociception, electromyogram, proto-oncogene proteins c-fos