Descending modulation of cardiac nociception by the rostral ventromedial medulla in rats
- VernacularTitle:延髓头端腹内侧区对大鼠心脏伤害性感受的下行调控作用
- Author:
Na SUN
1
;
Lingheng KONG
;
Ligang NIU
;
Juanxia ZHU
;
Yan XU
;
Jianqing DU
Author Information
1. 西安医学院基础医学研究所
- Keywords:
rostral ventromedial medulla;
cardiac nociception;
electrical stimulation;
electromyogram
- From:
Journal of Southern Medical University
2013;(11):1611-1614
- CountryChina
- Language:Chinese
-
Abstract:
Objective To observe the descending modulation of cardiac nociception by the rostral ventromedial medulla (RVM) in rats. Methods A rat model of cardiosomatic motor reflex (CMR) was established by injecting capsaicin into the pericardial sac to induce cardiac nociception, and the electromyogram (EMG) response of the dorsal spinotrapezius muscle was studied. The RVM was electricaly stimulated (25, 75 and 100 μA) or destroyed to examine whether RVM exerted descending modulation on cardiac nociception. Results Electrical stimulation of the RVM at 8 sites produced intensity-dependent inhibition of EMG responses to noxious cardiac stimulus (F[2,21]=43.188, P=0.001). Electrical stimulation at 3 sites caused facilitated EMG responses, but the increased magnitude of the EMG was not dependent on stimulation intensity (F[2,6]=0.884, P=0.461). Stimulation at 11 sites produced biphasic effects: at a low intensity (25 μA), the elicited EMG magnitude was significantly larger than baseline (P<0.05), and at greater intensities (75/100 μA), the stimulation caused suppression of the EMG magnitude to a level significantly lower than the baseline (P<0.05). Electrolytic lesion of the RVM resulted in significantly increased EMG responses compared with the baseline and sham lesion group. Conclusion Cardiac nociception evoked by capsaicin stimulation is subjected to descending biphasic modulation by the RVM, which produces predominantly descending inhibition on heart pain.
