title: Functional P2X7 receptors at cultured hippocampal astrocytes but not neurons.
abstract: P2X7 receptors have been suggested to be located both on neurons and astrocytes of the central and peripheral nervous systems. In the present Ca(2+)-imaging and patch-clamp study, we reinvestigated these findings on mixed neuronal-astrocytic cell cultures prepared from embryonic or newborn rat hippocampi. We found in a Mg(2+)-free bath medium that the prototypic P2X7 receptor agonist dibenzoyl-adenosine triphosphate (Bz-ATP) increased the intracellular Ca(2+) concentration ([Ca(2+)]i) both in the neuronal cell bodies and in their axo-dendritic processes only to a very minor extent. However, Bz-ATP produced marked [Ca(2+)]i transients in the neuronal processes, when they grew above a glial carpet, which was uniformly sensitive to Bz-ATP. These glial signals might be misinterpreted as neuronal responses because of the poor focal discrimination by a fluorescent microscope. Most astrocytes had a polygonal shape without clearly circumscribable boundaries, but a subgroup of them had neuron-like appearance. The cellular processes of this astrocytic subgroup, just as their cell somata and their polygonal counterparts, appeared to possess a high density of functional P2X7 receptors. In contrast to astrocytes, in a low Ca(2+)/no Mg(2+)-containing bath medium, hippocampal neurons failed to respond to Bz-ATP with membrane currents. In addition, neither the amplitude nor the frequency of spontaneous excitatory postsynaptic currents, representing the quantal release of glutamate, was modified by Bz-ATP. We conclude that cultured hippocampal neurons, in contrast to astrocytes, possess P2X7 receptors, if at all, only at a low density.
authors: Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, Haertelstrasse 16-18, 04107, Leipzig, Germany, Patrizia.Rubini@medizin.uni-leipzig.de.
authors: Patrizia
authors: P
authors: Rubini
authors: Gregor
authors: G
authors: Pagel
authors: Soghra
authors: S
authors: Mehri
authors: Peter
authors: P
authors: Marquardt
authors: Thomas
authors: T
authors: Riedel
authors: Peter
authors: P
authors: Illes
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000502:physiology*; D002478:Cells, Cultured; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D058486:Receptors, Purinergic P2X7 / Q000502:physiology*
chemical_list: D058486:Receptors, Purinergic P2X7