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Slices of guinea-pig cerebral cortex were incubated with [3H]-inositol at 37 degrees C before exposure to histamine or carbachol at 37 degrees C or 25 degrees C. Histamine-stimulated accumulation of [3H]-inositol 1-phosphate ([3H]-IP1) at 25 degrees C was only 5-7% of that at 37 degrees C, whereas for carbachol the response at 25 degrees C was 45-49% of that at 37 degrees C. The affinity of benzilylcholine, obtained from inhibition of carbachol-induced accumulation of [3H]-IP1 was similar at 25 degrees C and 37 degrees C, but the EC50 for carbachol was lower at 25 degrees C (20 +/- 2 microM) than at 37 degrees C (42 +/- 2 microM). The IC50 for histamine inhibition of [3H]-mepyramine binding to homogenates of guinea-pig cerebral cortex did not differ significantly at 25 degrees C and 37 degrees C. Histamine-induced accumulations of [3H]-IP2 and [3H]-IP3 at 25 degrees C, expressed as a percentage of the accumulation at 37 degrees C, were also much less than the corresponding value for carbachol. These observations imply that the locus or pathway(s) of agonist-induced formation of [3H]-IP1 are not the same for histamine and carbachol.

Original publication




Journal article


Br J Pharmacol

Publication Date





175 - 182


Animals, Carbachol, Cerebral Cortex, Guinea Pigs, Histamine, In Vitro Techniques, Inositol Phosphates, Male, N-Methylscopolamine, Pyrilamine, Scopolamine Derivatives, Sugar Phosphates, Temperature