The presynaptic effects of aspirin and prostaglandin E2 in the isolated cat heart.

The presynaptic effects of aspirin and prostaglandin E2 (PGE2) were evaluated in the isolated perfused cat heart preparation. Tissue catecholamine stores were studied by labelling the sympathetic nerve endings with [3H]-noradrenaline ([3H]-NA) and the effect of electric neural stimulation (5 Hz, 0.5 ms, 8 V, 60 s) was determined in the presence of drugs which inhibit neuronal or extraneuronal uptake, or antagonize alpha-adrenoceptors. [3H]-NA overflow was significantly increased by electric neural stimulation. Perfusion with 0.1 microM phentolamine increased transmitter overflow. Infusion of 0.1 microM PGE2 reduced the [3H]-NA overflow induced by electrical stimulation. Administration of 1 microM aspirin increased the [3H]-NA overflow and PGE2 prevented this effect of aspirin. The results support the view that PGEs participate in the negative feedback of transmitter release in the isolated perfused cat heart.