Effects of Quin-2, an intracellular Ca chelator, and TMB-8, an intracellular Ca antagonist, on the short-term desensitization to histamine in guinea pig taenia caecum.

The effects of Quin-2-acetoxylmethylester, an intracellular Ca ion chelator, and 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate-HCl (TMB-8), an intracellular Ca antagonist, on short-term desensitization to histamine were tested in guinea pig taenia caecum. Desensitization was induced by incubating the muscle with 10(-4) M histamine for 30 min and the recovery from the desensitization needed ca. 90 min. Both Quin-2-acetoxylmethylester (50 microM for 120 min) and TMB-8 (5 microM for 20 min) suppressed the desensitization. Modes of action and structures of both agents are quite different but both may reduce the availability of intracellular Ca ion. It is possible that reduction of intracellular Ca ion suppressed the desensitization.