The influence of H1- and H2-receptor blockade on responses of resistance and capacitance vessels to noradrenaline in working skeletal muscles in cats.

The effects of an H1- and H2-histamine receptor blockade upon the responses to noradrenaline (NA) of pre- and post-capillary segments of the microcirculation of the hind leg of cats were investigated. The responses to the resistance and capacitance vessels to noradrenaline injected in the coll. of femoral artery were reflected as changes in peripheral vascular resistance and in tissue volume respectively and determined during the following exercise before and after the H1 and H2-histamine receptor blockade. Muscular exercise was induced by sciatic nerve stimulation. The results show that H1- and H2-histamine receptor blockade applied together unmasked the vasodilator effects in both NA and that muscle exercise potentiated these effects in both pre- and post-capillary sections. This suggests that histamine may inhibit the response of the resistance and capacitance vessels in the working skeletal muscles to noradrenaline.