Basal levels of adenosine modulate mGluR5 on rat hippocampal astrocytes

Neuronal activity elicits increases in intracellular Ca2+ in astrocytes, wh ich in turn can elevate neuronal Ca2+ and potentiate the efficacy of excita tory synaptic transmission. Therefore, understanding the modulation of astr ocyte Ca2+ elevations by neurotransmitters should aid in understanding astr ocyte-neuronal interactions. On cultured hippocampal microislands containin g only astrocytes, activation of metabotropic glutamate receptors (mGluRs) with the specific agonist 1S,3R-ACPD triggers Ca2+ elevations that are pote ntiated by adenosine A1 receptor activation. A1 receptor modulation of mGlu R-induced Ca2+ elevations is blocked by pertussis toxin and is mimicked by the wasp venom peptide mastoparan, suggesting that potentiation occurs by m eans of a G(i/o) mechanism. Surprisingly, on microislands containing only a strocytes, A1 receptor antagonism or adenosine degradation suppresses mGluR -triggered Ca2+ elevations, strongly suggesting that astrocytes are a sourc e of physiologically relevant concentrations of adenosine. GLIA 33:24-35, 2 001. (C) 2001 Wiley-Liss, Inc.