Effect of endothelin-1 injected into rostral ventrolateral medulla on cardiovascular responses in cats

AIM: To study the effect of endothelin-1 (ET-1) in the rostral ventrolatera l medulla ( rVLM) on cardiovascular responses in cats. METHODS: The stereot atic technique and microinjection method were used. RESULTS: ET-1(4 mu mol. L-1 0.5 mu L) microinjected into rVLM induced mean arterial pressure (MAP) increasing (3.7 +/- 1.3) kPa, heart rate (HR) accelerating (29 +/- 7) beats min-l, and renal nerve activity (RNA) intensifying 45 % +/- 10 %. The effe cts were dose-dependent. Before and after bilateral vagotomy, there was no significant difference in the reaction of MAP, HR, and RNA. After intraveno us injection with phentolamine (5 mg.kg(-1), alpha-blocker), ET-1 did not i nduce significant change of MAP. ET-1 raised the content of peripheral plas ma argipressin (Arg) from (12.4 +/- 6.5) to (70.3 +/- 24.2) ng L-1 with rad ioimmunoassay, and showed a correlation with MAP changes. ET-1 induced hear t rhythm disorder (HRhD) in acute myocardiac ischemia, the occur time of HR hD was (4.8 +/- 2.9) min, and the score was 4.4 +/- 1.6, and it was signifi cantly different from control. CONCLUSION: ET-1 microinjected into rVLM cou ld involve with control regulation of cardiovascular and sympathetic nerve activity.