ABSTRACT
Objective evaluate the role of vagus nerve?muscarinic cholinergic receptor ( M recep?tor) pathway in mitigation of myocardial ischemia?reperfusion (I∕R) injury by intrathecal morphine postcon?ditioning in rats. Methods Seventy adult male Sprague?Dawley rats in which intrathecal catheters were suc?cessfully placed without complications, weighing 250-350 g, were randomly assigned into 7 groups ( n=10 each) using a random number table:sham operation group (Sham group), I∕R group, intrathecal morphine postconditioning group ( MP group) , vagal transection ( VT) group, VT+ intrathecal morphine postcondi?tioning group (VT+MP group), atropine (ATP, M receptor antagonist) + morphine postconditioning group ( ATP+MP group) , and ATP group. Myocardial I∕R was produced by occlusion of the anterior descending branch of left coronary artery for 30 min followed by 2 h of reperfusion. Morphine ( 3μg∕kg, 10μl) was in?trathecally infused over 5 min starting from onset of reperfusion in MP group. Normal saline 10 μl was in?trathecally infused over 5 min starting from onset of reperfusion in NS group. The bilateral vagus nerves were transected at 10 min before reperfusion in VT+MP group. Atropine ( 0?1 mg∕kg, 0?5 ml) was intravenously infused over 5 min starting from 10 min before reperfusion in ATP+MP group. The occurrence of cardiac ar? rhythmia ( premature ventricular contractions ( PVCs) and ventricular tachycardia ( VT)∕ventricular fibrilla?tion ( VF) ) within the first 30 min of reperfusion was recorded. The rats were sacrificed at 120 min of reper?fusion, and myocardial specimens were obtained for determination of myocardial infarct size ( IS) as a per?centage of area at risk (AAR). IS∕AAR ratio was calculated. Results Compared with Sham group, the number of PVCs and VT∕VF and IS∕AAR ratio were significantly increased in the other groups. Compared with I∕R group, the number of PVCs and VT∕VF and IS∕AAR ratio were significantly decreased in MP group. Compared with MP group, the number of PVCs and VT∕VF and IS∕AAR ratio were significantly in?creased in VT+MP and ATP+MP groups. Conclusion Vagus nerve?M receptor pathway is involved in miti?gation of myocardial I∕R injury by intrathecal morphine postconditioning in rats.
ABSTRACT
Objective To investigate the relationship between cardiac vagus nerves and changes of connexins(Cx)and intracellular gap junction(GJ)distribution pattern in superior vena cava(SVC)myosleeve in dog with atrial fibrillation(AF).Methods Twenty four hybrid dogs were divided into sham operation group(Sham group,n=8),SVC-AO fat pad removed group(RM group,n=8)and SVC-AO fat pad reserved group(RS group,n=8).In RM group and RS group,right atrial pacing was performed at a frequency of 500～650/min for 6 weeks to establish AF model.AF was induced by programmed stimulation or burst stimulation of atrial pacing.The expression and distribution of Cx40 and Cx43 in the SVC myosleeve tissue in three groups were analyzed by immunofluorescence staining.Transmission electron microscopy was used to observe the uhrastructural organization of gap junction(GJ).Results The rate of inducing sustained AF(＞ 15 min)in RS group was significantly higher than that in RM group (P ＜ 0.01).The expression of Cx40 and Cx43 in the SVC myosleeve in sham group and RS group were significantly higher than that in RM group(P ＜ 0.05).Furthermore,the expression of Cx40 and Cx43 in RS group were obviously higher than that in sham group(P ＜0.05).The ratio of end-to-end to side-to-side in RS group was lower than that in Sham group and RM group.Comparing with RM group,the channel of GJ became shorter and wider in RS group(P ＜0.05).Sarcomere was dissolved and mitochondrion showed vacuole degeneration in RS group.Conclusion The remodeling of Cx40 and Gx43 in SVC myosleeve tissue may be mediated by vagus nerves.It is conducive to the maintenance and stability of AF.However,this effect can be weakened by removing SVC-AO fat pad of canine.