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This Article Full Text Full Text (PDF) All Versions of this Article: 573/3/753    most recent jphysiol.2006.108613v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shiokawa, H. Articles by Yoshimura, M. Search for Related Content PubMed PubMed Citation Articles by Shiokawa, H. Articles by Yoshimura, M. Related Collections Neuroscience

¹ Department of Integrative Physiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
² Department of Physiology, Faculty of Medicine, Saga University, Saga 849-8501, Japan
³ Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan

ATP mediates somatosensory transmission in the spinal cord through the activation of P2X receptors. Nonetheless, the functional significance of postsynaptic P2X receptors in spinal deep dorsal horn neurones is still not yet well understood. Using the whole-cell patch-clamp technique, we investigated whether the activation of postsynaptic P2X receptors can modulate the synaptic transmission in lamina V neurones of postnatal day (P) 9–12 spinal cord slices. At a holding potential of –70 mV, ATPS (100 µM), a nonhydrolysable ATP analogue, generated an inward current, which was resistant to tetrodotoxin (1 µM) in 61% of the lamina V neurones. The ATPS-induced inward current was accompanied by a significant increase in the frequency of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) in the majority of lamina V neurones. The ATPS-induced inward current was not reproduced by P2Y receptor agonists, UTP (100 µM), UDP (100 µM), and 2-methylthio ADP (100 µM), and it was also not affected by the addition of guanosine-5'-O-(2-thiodiphosphate) (GDPßS) into the pipette solution, thus suggesting that ionotropic P2X receptors were activated by ATPS instead of metabotropic P2Y receptors. On the other hand, ,ß-methylene ATP (100 µM) did not change any membrane current, but instead increased the mEPSC frequency in the majority of lamina V neurones. The ATPS-induced inward current was suppressed by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) (10 µM), but not by trinitrophenyl-ATP (TNP-ATP) (1 µM). Furthermore, we found that ATPS (100 µM) produced a clear inward current which was observed in all lamina V neurones over P16 spinal cord slices, in contrast to P9–12. These results indicate that distinct subtypes of P2X receptors were functionally expressed at the post- and presynaptic sites in lamina V neurones, both of which may contribute to the hyperexcitability of lamina V in a different manner. In addition, the data relating to the developmental increase in the functional P2X receptors suggest that purinergic signalling may thus be more common in somatosensory transmission with maturation.

(Received 1 March 2006; accepted after revision 12 April 2006; first published online 13 April 2006)
Corresponding author T. Nakatsuka: Department of Physiology, Faculty of Medicine, Saga University, Saga 849-8501, Japan. Email: nakatsuk{at}cc.saga-u.ac.jp

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