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Somatic and axonal effects of ATP via P2X 2 but not P2X 7 receptors in rat thoracolumbar sympathetic neurones
Author(s) -
Allgaier C.,
Reinhardt R.,
Schädlich H.,
Rubini P.,
Bauer S.,
Reichenbach A.,
Illes P.
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02498.x
Subject(s) - ppads , p2 receptor , receptor , adenosine triphosphate , excitatory postsynaptic potential , chemistry , medicine , agonist , biology , endocrinology , microbiology and biotechnology , biochemistry
Excitatory ATP responses in rat cultured thoracolumbar sympathetic neurones are mediated by somatic P2X 2 receptors. The present study investigated a possible role of axonal P2X 2 as well as P2X 7 receptors on the same preparation. Confocal laser scanning microscopy demonstrated P2X 2 and P2X 7 immunoreactivity along the axons as well as P2X 7 immunoreactivity surrounding the cell nuclei. P2X 7 mRNA expression was detected in individual neurones using a single‐cell RT–PCR approach. Adenosine triphosphate (ATP) caused a significant increase in axonal Ca 2+ concentration which was dependent on external Ca 2+ but insensitive to depletion of the cellular Ca 2+ pools by cyclopiazonic acid. Pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulfonate (PPADS; 30 µ m ) virtually abolished the ATP response, whereas brilliant blue G (0.1 µ m ), a selective P2X 7 receptor antagonist, had no effect. Dibenzoyl‐ATP (BzATP; 100 µ m ) induced a much smaller increase in axonal [Ca 2+ ] concentration than ATP at equimolar concentrations. The response to BzATP was distinctly reduced by PPADS but not by brilliant blue G. The overall pharmacological profile of the axonal P2X receptors resembled closely that of the somatic P2X 2 receptors. In conclusion, the present data suggest the occurrence of axonal excitatory P2X 2 receptors in thoracolumbar sympathetic neurones. However, the functional significance of axonal and (peri)‐nuclear P2X 7 receptors has still to be proven.