Although growing evidence suggests that extracellular ATP might play roles in the control of astrocyte/neuron crosstalk in the CNS by acting on P2X7 receptors, it is still unclear whether neuronal functions can be attributed to P2X7 receptors. In the present paper, we investigate the location, pharmacological profile, and function of P2X7 receptors on cerebrocortical nerve terminals freshly prepared from adult rats, by measuring glutamate release and calcium accumulation. The preparation chosen (purified synaptosomes) ensures negligible contamination of non‐neuronal cells and allows exposure of ‘nude’ release‐regulating pre‐synaptic receptors. To confirm the results obtained, we also carried out specific experiments on human embryonic kidney 293 cells which had been stably transfected with rat P2X7 receptors. Together, our findings suggest that (i) P2X7 receptors are present in a subpopulation of adult rat cerebrocortical nerve terminals; (ii) P2X7 receptors are localized on glutamatergic nerve terminals; (iii) P2X7 receptors play a significant role in ATP‐evoked glutamate efflux, which involves Ca2+‐dependent vesicular release; and (iv) the P2X7 receptor itself constitutes a significant Ca2+‐independent mode of exit for glutamate.

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Glutamate release induced by mild depolarization was studied in astroglial preparations from the adult rat cerebral cortex, that is acutely isolated glial sub-cellular particles (gliosomes), cultured adult or neonatal astrocytes, and neuron-conditioned astrocytes.

The receptor mechanisms regulating the ATP-induced free cytosolic Ca 2+ concentration ([Ca 2+ ] i ) changes in cultured rat cortical type-1 astrocytes were analyzed using fura-2-based Ca 2+ imaging microscopy. Upon prolonged ATP challenge (1^100 W WM), astroglial cells displayed a biphasic [Ca 2+ ] i response consisting of an initial peak followed by a sustained elevation. Suramin and pyridoxalphosphate-6-azophenyl-2P P,4P P-disulfonic acid blocked both components, albeit to a di¡erent extent. By contrast, the selective P2X7 antagonist oxidized ATP irreversibly abrogated the sustained [Ca 2+ ] i signal without a¡ecting the transient phase. Finally, astrocyte challenge with the selective P2X7 agonist 3P P-O-(4-benzoyl)benzoyl-ATP evoked a sustained [Ca 2+ ] i elevation, which occluded that induced by ATP. We can conclude that in cultured cortical astrocytes the ATP-mediated sustained [Ca 2+ ] i rise does not implicate capacitative Ca 2+ entry but involves Ca 2+ in£ux through P2X7-like receptors. ß

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The presynaptic P2X 7 receptor (P2X 7 R) plays an important role in the modulation of transmitter release. We recently demonstrated that, in nerve terminals of the adult rat cerebral cortex, P2X 7 R activation induced Ca 2+ -dependent vesicular glutamate release and significant Ca 2+ -independent glutamate efflux through the P2X 7 R itself. In the present study, we investigated the effect of the new selective P2X 7 R competitive antagonist 3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methyl pyridine (A-438079) on cerebrocortical terminal intracellular calcium (intrasynaptosomal calcium concentration; [Ca 2+ ] i ) signals and glutamate release, and evaluated whether P2X 7 R immunoreactivity was consistent with these functional tests. A-438079 inhibited functional responses. P2X 7 R immunoreactivity was found in about 45% of cerebrocortical terminals, including glutamatergic and non-glutamatergic terminals. This percentage was similar to that of synaptosomes showing P2X 7 R-mediated [Ca 2+ ] i signals. These findings provide compelling evidence of functional presynaptic P2X 7 R in cortical nerve terminals.

The aims of this study are to determine the chemical composition of Lavandula angustifolia Mill. and Coriandrum sativum L. essential oils, to evaluate their cytotoxic effects in SH-SY5Y human neuroblastoma cells, to investigate whether an alteration of adenylate cyclase 1 (ADCY1) and of extracellular signal-regulated kinase (ERK) expression can take part in the molecular mechanisms of the essential oils, and to study their possible neuronal electrophysiological effects. The essential oils were obtained by hydrodistillation, and studied by GC and GC-MS. In the oils from L. angustifolia and C. sativum, linalool was the main component (33.1% and 67.8%, respectively). SH-SY5Y cells were incubated with different concentrations of essential oils and of linalool. Cell viability and effects on ADCY1 and ERK expression were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT and Western blotting, respectively. Variation in cellular electrophysiology was studied in primary cultures of rat cortical neurons with a multi-electrode array (MEA)-based approach. The essential oils and linalool revealed different cytotoxic activities. Linalool inhibited ADCY1 and ERK expression. Neuronal networks subjected to L. angustifolia and C. sativum essential oils showed a concentration-dependent inhibition of spontaneous electrical activity.

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