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Differential effect of temperature on histamine‐ and carbachol‐stimulated inositol phospholipid breakdown in slices of guinea‐pig cerebral cortex
Author(s) -
Carswell Heather,
Galione A.G.,
Young J.M.
Publication year - 1987
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1987.tb16838.x
Subject(s) - carbachol , histamine , mepyramine , inositol , guinea pig , endocrinology , inositol phosphate , medicine , chemistry , agonist , biology , receptor , biochemistry , stimulation , antagonist
1 Slices of guinea‐pig cerebral cortex were incubated with [ 3 H]‐inositol at 37°C before exposure to histamine or carbachol at 37°C or 25°C. Histamine‐stimulated accumulation of [ 3 H]‐inositol 1‐phosphate ([ 3 H]‐IP 1 ) at 25°C was only 5–7% of that at 37°C, whereas for carbachol the response at 25°C was 45–49% of that at 37°C. 2 The affinity of benzilylcholine, obtained from inhibition of carbachol‐induced accumulation of [ 3 H]‐IP 1 was similar at 25°C and 37°C, but the EC 50 for carbachol was lower at 25°C (20 ± 2 μ m ) than at 37°C(42 ± 2 μ m ). 3 The IC 50 for histamine inhibition of [ 3 H]‐mepyramine binding to homogenates of guinea‐pig cerebral cortex did not differ significantly at 25°C and 37°C. 4 Histamine‐induced accumulations of [ 3 H]‐IP 2 and [ 3 H]‐IP 3 at 25°C, expressed as a percentage of the accumulation at 37°C, were also much less than the corresponding value for carbachol. 5 These observations imply that the locus or pathway(s) of agonist‐induced formation of([ 3 H]‐IP 1 ) are not the same for histamine and carbachol.