Activation of Muscarinic and of α1‐Adrenergic Receptors on Astrocytes Results in the Accumulation of Inositol Phosphates

Abstract

Astrocyte-enriched cultures prepared from the newborn rat cortex incorporated [³H]myo-inositol into intracellular free inositol and inositol lipid pools. Noradrenaline and carbachol stimulated the turnover of these pools resulting in an increased accumulation of intracellular [³H]inositol phosphates. The effects of noradrenaline and carbachol were dose-dependent and blocked by specific α₁-adrenergic and muscarinic cholinergic receptor antagonists, respectively. The increase in [³H]inositol phosphate accumulation caused by these receptor antagonists was virtually unchanged when cultures were incubated in Ca²⁺ -free medium, but was abolished when EGTA was also present in the Ca²⁺ -free medium. Cultures of meningeal fibroblasts, the major cell type contaminating the astrocyte cultures, also accumulated [³H]myo-inositol, but no increased accumulation of [³H]inositol phosphates was found in response to either noradrenaline or carbachol.