Myles ME, Fain JN. Carbachol, but not norepinephrine, NMDA, ionomycin, ouabain, or phorbol myristate acetate, increases inositol 1,3,4,5-tetrakisphosphate accumulation in rat brain cortical slices.
J Neurochem 1994;
62:2333-9. [PMID:
8189237 DOI:
10.1046/j.1471-4159.1994.62062333.x]
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Abstract
Ionomycin, a Ca2+ ionophore, stimulated phosphoinositide breakdown in rat brain cortical slices incubated in the presence of 1.2 mM Ca2+, but, unlike muscarinic cholinergic stimulation, it had little effect on inositol 1,3,4,5-tetrakisphosphate accumulation. However, at 2 min, the increase in inositol 1,4,5-trisphosphate due to 10 microM ionomycin was equivalent to that seen with 1 mM carbachol. Phorbol 12-myristate 13-acetate or high K+ (30 mM) increased inositol 1,4,5-trisphosphate, but not inositol 1,3,4,5-tetrakisphosphate accumulation. The stimulation of inositol 1,4,5-trisphosphate accumulation due to ionomycin, unlike that seen with carbachol, was abolished in buffer containing 0.2 mM Ca2+. The increase in inositol 1,3,4,5-tetrakisphosphate accumulation in brain slices due to 1 mM carbachol ranged from 55 to 68% of that for inositol 1,4,5-trisphosphate. Norepinephrine, NMDA, veratridine, and ouabain also increased inositol 1,4,5-trisphosphate, but had minimal effects on inositol 1,3,4,5-tetrakisphosphate accumulation. These results suggest that there is something unique about the stimulation of inositol 1,3,4,5-tetrakisphosphate accumulation by carbachol, which is also the only one of these agents that is able to activate phosphoinositidase C beta 1 in isolated rat brain membranes.
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