TNP-ATP-resistant P2X ionic current on the central terminals and somata of rat primary sensory neurons.
P2X receptors have been suggested to be expressed on the central terminals of A delta-afferent fibers innervating dorsal horn lamina V and play a role in modulating sensory synaptic transmission. These P2X receptors have been widely thought to be P2X2+3 receptors. However, we have recently found that P2X receptor-mediated modulation of sensory transmission in lamina V is not inhibited by trinitrophenyl-adenosine triphosphate (TNP-ATP), a potent antagonist of P2X1, P2X3 homomers, and P2X2+3 heteromers. To provide direct evidence for the presence of TNP-ATP-resistant P2X receptors on primary afferent fibers, we examined alpha,beta-methylene-ATP (alpha beta meATP)-evoked currents and their sensitivity to TNP-ATP in rat dorsal root ganglion (DRG) neurons. alpha beta meATP evoked fast currents, slow currents, and mixed currents that contained both fast and slow current-components. Fast currents and fast current components in the mixed currents were both completely inhibited by 0.1 microM TNP-ATP (n = 14). Both slow currents and slow-current components in the mixed currents showed broad spectrum of sensitivity to 1 microM TNP-ATP, ranging from complete block (TNP-ATP-sensitive) to little block (TNP-ATP-resistant). TNP-ATP-resistant currents evoked by 10 microM alpha beta meATP could be largely inhibited by 10 microM iso-pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid. Cells with P2X currents that were highly resistant to TNP-ATP were found to be insensitive to capsaicin. These results suggest that TNP-ATP-resistant P2X receptor subtypes are expressed on capsaicin-insensitive A delta-afferent fibers and play a role in modulating sensory transmission to lamina V neurons.
Tsuzuki
Kenzo
K
Department of Oral and Maxillofacial Surgery, McKnight Brain Institute and College of Dentistry, University of Florida, Gainesville, Florida 32610, USA.
Ase
Ariel
A
Séguéla
Philippe
P
Nakatsuka
Terumasa
T
Wang
Cong-Yi
CY
She
Jin-Xiong
JX
Gu
Jianguo G
JG
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission
D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002211:Capsaicin