Positive chronotropic and inotropic responses to lysophosphatidylcholine are mediated by norepinephrine released from myocardial sympathetic nerve terminals.

Abstract

1. The effects of beta-adrenoceptor blockade and reserpinization on the positive chronotropic and inotropic responses to lysophosphatidylcholine (LPC) were examined in isolated atrial and ventricular preparations from rat hearts. 2. The positive responses to 10(-4) M LPC were about 40-55% of those to 10(-5) M norepinephrine (NE) in each preparation. 3. The responses to LPC in the presence of propranolol or in the reserpinized preparations were significantly smaller than the corresponding values obtained in control preparations, and were about 10-25% of those to NE. 4. It was concluded that positive chronotropic and inotropic responses to LPC are at least partially mediated by release of NE from myocardial sympathetic nerve terminals.