Somatic and axonal effects of ATP via P2X2 but not P2X7 receptors in rat thoracolumbar sympathetic neurones.
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 micro m) virtually abolished the ATP response, whereas brilliant blue G (0.1 micro m), a selective P2X(7) receptor antagonist, had no effect. Dibenzoyl-ATP (BzATP; 100 micro 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.
Allgaier
C
C
Rudolf-Boehm-Institute of Pharmacology and Toxicology, Department of Neurophysiology, University of Leipzig, Leipzig, Germany. allgc@medizin.uni-leipzig.de
Reinhardt
R
R
Schädlich
H
H
Rubini
P
P
Bauer
S
S
Reichenbach
A
A
Illes
P
P
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D007150:Immunohistochemistry; D008161:Lumbosacral Region; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058476:Receptors, Purinergic P2X2; D058486:Receptors, Purinergic P2X7; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics
C546403:P2rx2 protein, rat; C546470:P2rx7 protein, rat; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058486:Receptors, Purinergic P2X7; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D014446:Tyrosine 3-Monooxygenase; D002118:Calcium