Muscarinic receptor‐induced calcium responses in astroglia

Abstract

Background:The objective of this study was to characterize and quantitate the calcium responses to cholinergic stimulation in individual primary rat cortical astrocytes and human 132 1N1 astrocytoma cells. Materials and Methods:The fluorescent calcium probe Indo-1 AM and an attached cell analysis and sorting (ACAS) instrument were used to quantitate calcium responses in these cells. Results: A concentration-dependent response to carbachol was seen in both cell types. However, carbachol was more potent and efficacious, and the response was more homogeneous in the cell line. The calcium response was mediated by the M3 subtype of muscarinic receptors. Experiments in the absence of extracellular calcium and with EGTA demonstrated that the initial calcium spike

Role of phospholipase D signaling in ethanol‐induced inhibition of carbachol‐stimulated DNA synthesis of 1321N1 astrocytoma cells

“…Over the past few years we have identified several intracellular pathways by which activation of muscarinic M3 receptors induces proliferation of astroglial cells (Guizzetti et al , 1998Catlin et al 2000b;Guizzetti and Costa 2000a, 2002Yagle et al 2001). We also found that ethanol inhibits carbachol-induced DNA synthesis in astroglial cells and that only selective signaling molecules activated by carbachol are affected by concentrations of ethanol capable of inhibiting cell proliferation.…”

“…Such mitogenic effect appears to be mediated by two intracellular signaling pathways, one leading to the activation of phospholipase C (PLC), protein kinase C (PKC) e and mitogen-activated protein kinase (MAPK), and another involving phosphatidylinositol-3-kinase (PI-3K), PKC f, 70-kDa ribosomal S6 kinase (p70S6K) and nuclear factor-jB (NF-jB) (Guizzetti et al 1998(Guizzetti et al , 2003aCatlin et al 2000b;Costa 2000a, 2001;Yagle et al 2001). Selective inhibition of each of these enzymes leads to inhibition of carbachol-induced cell proliferation, suggesting that both pathways are required for carbacholinduced DNA synthesis.…”

Cytoplasmic Ca2+ concentration changes evoked by cholinergic stimulation in primary astrocyte cultures prepared from the rat cochlear nucleus

“…In the experiment of Fig. 3A, the 1 mM CCh-induced Ca 2+ transient was blocked by the application of 10 lM (Catlin et al, 2000) atropine, while in Fig. 3C 10 lM (Hösli et al, 2001) muscarine evoked a plateau-type response that could be fully blocked by 10 lM atropine, too.…”

“…Although the heterogeneity of the CCh-evoked responses was pronounced in these experiments, 50-100 lM CCh regularly evoked Ca 2+ transients in the responding cells. Generally, these values are higher than most of those used in other brain preparations, although in some cases applications of even millimolar CCh concentrations for evoking maximal cholinergic response have also been reported (Shao and McCarthy, 1995;Catlin et al, 2000). In the present experiments the certainly supramaximal 1 mM CCh was chosen in order to ensure well-detectable cytoplasmic Ca 2+ concentration increases in all astrocytes that were sensitive to cholinergic stimulation.…”

“…It is not surprising, therefore, that the presence of both muscarinic (see e.g. Porter and McCarthy, 1997;Verkhratsky et al, 1998;Catlin et al, 2000) and nicotinic (Oikawa et al, 2005;Xiu et al, 2005) ACh receptors has been well documented in astrocytes in (or isolated from) various brain areas. As the role of ACh in modulating CN signal processing has been proven (Chen et al, 1994(Chen et al, , 1998Sherriff and Henderson, 1994;Zhang and Kaltenbach, 2000;Fujino and Oertel, 2001;Oertel and Fujino, 2001), the occurrence of ACh receptors in this nucleus was highly probable.…”