Effects of treatment with pyridostigmine on ECG, hemodynamics and connexin 43 after acute myocardial infarct in anesthetized rats (1169.13)

Abstract

We evaluated the effect of acute treatment with pyridostigmine (PYR) an acetilconinesterase inhibitor on hemodynamics, ECG, survival rate and connexin 43 (Cx43), shortly after myocardial infarction (MI) in anesthetized rats.Rats were anesthetized with urethane, and instrumented for ECG and arterial pressure (AP) recordings. After basal recordings, acute MI was induced by left coronary artery ligation followed by treatment with PYR (0.25 mg/kg, iv), or saline. ECG and AP were monitored during for 4h after MI when the animals had their hearts removed and retrogradely perfused with a Evans blue dye to determine the size of myocardial ischemia. The amount of Cx43 in left ventricle was also evaluated, by Western blot technique, in left ventricle of infarcted rats.PYR caused a mild reduction in heart rate (438±8 to 387±10 bpm) with no change in AP. Infarcted rats treated with PYR showed lower incidence of arrhythmias and the percentage of rats that survived until the 4th hour after infarction was also higher in subjects that received PYR (72 vs 58%). Lengthening of QTc interval (Δ=33±13 ms) was observed in non‐treated, but not in PYR treated rats (Δ=‐2±4 ms). Finally, the amount of Cx43 in left ventricle was markedly reduced after MI (2.2±0.4 vs 0.72±0.1 au in non‐infarcted control rats). PYR administration also prevented the reduction in Cx43 (1.31±0.29 au) of infarcted rats.Grant Funding Source: Supported by FAPESP, CNPq, CAPES, FAEPA.