Orexins activates protein kinase C-mediated Ca(2+) signaling in isolated rat primary sensory neurons.
Previous results have suggested that orexins causes a rise of intracellular free calcium ([Ca(2+)](i)) in cultured rat dorsal root ganglion (DRG) neurons, implicating a role in nociception, but the underlying mechanism is unknown. Hence, the aim of the present study was to investigate whether the orexins-mediated signaling involves the PKC pathways in these sensory neurons. Cultured DRG neurons were loaded with 1 micromol Fura-2 AM and [Ca(2+)](i) responses were quantified by the changes in 340/380 ratio using fluorescence imaging system. The orexin-1 receptor antagonist SB-334867-A (1 microM) inhibited the calcium responses to orexin-A and orexin-B (59.1+/-5.1 % vs. 200 nM orexin-A, n=8, and 67+/-3.8 % vs. 200 nM orexin-B, n=12, respectively). The PKC inhibitor chelerythrine (10 and 100 microM) significantly decreased the orexin-A (200 nM)-induced [Ca(2+)](i) increase (59.4+/-4.8 % P<0.01, n=10 and 4.9+/-1.6 %, P<0.01, n=9) versus response to orexin-A). It was also found that chelerythrine dose-dependently inhibited the [Ca(2+)](i) response to 200 nM orexin-B. In conclusion, our results suggest that orexins activate intracellular calcium signaling in cultured rat sensory neurons through PKC-dependent pathway, which may have important implications for nociceptive modulation and pain.
Ozcan
M
M
Department of Physiology, Firat University Faculty of Medicine, Elazig, Turkey.
Ayar
A
A
Serhatlioglu
I
I
Alcin
E
E
Sahin
Z
Z
Kelestimur
H
H
D000818:Animals; D001583:Benzoxazoles / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000166:cytology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000494:pharmacology; D009287:Naphthyridines; D009479:Neuropeptides / Q000378:metabolism* / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism; D000068797:Orexins; D010146:Pain / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011984:Sensory Receptor Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology
C420062:1-(2-methylbenzoxazol-6-yl)-3-(1,5)naphthyridin-4-yl urea; D001583:Benzoxazoles; D047908:Intracellular Signaling Peptides and Proteins; D009287:Naphthyridines; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D000068797:Orexins; D014508:Urea; D011493:Protein Kinase C