Effects of capsaicin on release of substance P-like immunoreactivity and physiological parameters in isolated perfused guinea-pig heart

Release of substance P-like immunoreactivity (SP-LI) was measured from isolated perfused guinea-pig hearts. Capsaicin (1 microM) caused a substantial increase in the amount of SP-LI detected in perfusate compared to values during exposure to vehicle or drug-free buffer. Tachyphylaxis developed to the effect of capsaicin on release of SP-LI and to its effect on physiological parameters. These data show SP-LI can be released from cardiac sensory nerves and suggest SP could mediate a portion of the response of the isolated heart to capsaicin.