Abstract
To understand the contractile response to histamine, drug-induced tension developments were measured in intact and staphylococcal α-toxin-treated permeabilized smooth muscle preparations of rabbit lingual artery. Histamine produced an endothelium-independent contraction; the observed effect was antagonized by diphenhydramine and was attenuated by nifedipine. Histamine produced only transient contraction in the Ca2+-free bathing media. In permeabilized preparations, histamine-induced contraction was abolished by ryanodine (in the presence of caffeine) or prior repeated application of caffeine; however, contraction produced by IP3 was still observed under the same experimental condition as that of the histamine study. Histamine- or caffeine-induced contraction was abolished in the permeabilized preparations by prior repeated application of IP3; caffeine or IP3 produced contraction after repeated application of histamine. Ryanodine in the presence of histamine was ineffective on caffeine-induced contraction, suggesting that histamine by itself may not have the ability to act on caffeine-sensitive Ca2+ release channels. Neomycin and H-7 completely abolished the histamine-induced contraction. Hence, it is suggested that histamine can contract the lingual artery via H1-receptor-coupled phospholipase C activation, and the contraction consists of a phasic response evoked by Ca2+ release from the IP3- and caffeine-sensitive Ca2+ storage site and the tonic response generated by the voltage-dependent influx of Ca2+. It is also postulated that IP3 produced by histamine may be able to produce Ca2+ release from only a part of the intracellular Ca2+ stores in the smooth muscle of rabbit lingual artery.
