CHOLINERGIC-SYMPATHETIC INTERACTIONS IN THE LEFT ATRIUM AND LEFT-VENTRICLE OF CONSCIOUS DOGS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 225  (1) , 219-223
Abstract
The extent of cholinergic-sympathetic interaction in the heart was examined in the resting control state and after isoproterenol stimulation in 8 conscious dogs. Sonomicrometer crystals and solid-state pressure transducers were implanted in the left atrium and the left ventricle to evaluate mechanical function while heart rate was held constant by atrial pacing. Edrophonium (0.5 mg/kg i.v.) was given as a single dose at rest and during increased sympathetic tone produced by continuous infusion of isoproterenol (0.08 .mu.g/kg per min). In the control state, edrophonium administration caused no change in left ventricular of dP/dt, fractional shortening or velocity of contraction, but produced significant (P < 0.001) decreases in left atrial fractional shortening and contraction velocity. During isoproterenol infusion there were significant increases in dP/dt, the velocity of contraction and fractional shortening in both left atrium and ventricle (P < 0.001). Administration of edrophonium during this increase in inotropic state produced significant (P < 0.01) decreases in left ventricular dP/dt, fractional shortening and contraction velocity. After edrophonium, left atrial fractional shortening and velocity of contraction were decreased to values that were significantly (P < 0.001) less than control. Cholinergic stimulation apparently caused selective depression of left atrial systolic function at rest and depression of both left atrial and ventricular function during sympathetic stimulation.

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