Cardiac nociceptive reflexes: role of kinins, prostanoids and capsaicin-sensitive afferents

Spinal sympathetic afferent fibres with endings in the heart are essential for signalling cardiac pain. In anesthetized, open-chest dogs, stimulation of these cardiac afferents with the algesic agents, bradykinin or capsaicin, results in reflex increases in arterial pressure and cardiac rate. The reflex responses induced by bradykinin are enhanced by concomitant application of prostaglandins of the E type or prostacyclin, and reduced by indomethacin. In contrast, the reflex effects of capsaicin are not influenced by either indomethacin or prostaglandin E1 treatment. Evidence is presented that reflexogenic effects of bradykinin involve its interaction with specific B2-receptors for kinins and that proteolysis of endogenous kininogen precursor to kinins by epicardially applied tissue kallikrein can initiate reflex cardiovascular effects.