Acid-sensing ion channels contribute to the metaboreceptor component of the exercise pressor reflex

The exercise pressor reflex is evoked by both mechanical and metabolic stimuli arising in contracting skeletal muscle. Recently, the blockade of acid-sensing ion channels (ASICs) with amiloride and A-316567 attenuated the reflex. Moreover, amiloride had no effect on the mechanoreceptor component of the reflex, prompting us to determine whether ASICs contributed to the metaboreceptor component of the exercise pressor reflex. The metaboreceptor component can be assessed by measuring mean arterial pressure during postcontraction circulatory occlusion when only the metaboreceptors are stimulated. We examined the effects of amiloride (0.5 microg/kg), A-317567 (10 mM, 0.5 ml), and saline (0.5 ml) on the pressor response to and after static contraction while the circulation was occluded in 30 decerebrated cats. Amiloride (n = 11) and A-317567 (n = 7), injected into the arterial supply of the triceps surae muscles, attenuated the pressor responses both to contraction while the circulation was occluded and to postcontraction circulatory occlusion (all, P < 0.05). Saline (n = 11), however, had no effect on the pressor responses to contraction while the circulation was occluded or to postcontraction circulatory occlusion (both, P > 0.79). Our findings led us to conclude that ASICs contribute to the metaboreceptor component of the exercise pressor reflex.