抄録
It was reported that gap junction channels exist between primary sensory neurons in the mesencephalic trigeminal nucleus (MesV) that innervate jaw-closing muscle spindles and periodontal mechanoreceptors. Recently, the gating kinetics of gap junction channels has been well investigated in insect cell lines and Xenopus oocytes. Here we focused on the electrophysiological properties of gap junction channels between MesV neurons. We made dual whole-cell patch-clamp recordings from such a pair of MesV neurons that contacted each other with a large area of plasma membrane, using slice preparations of 10-17 day old rats. We applied ramp pulses (0.1-4 V/sec) to one cell under V-clamp conditions and recorded the responses in the other cell under V-clamp and I-clamp conditions. Of 9 paired recordings, 4 pairs showed inward rectification with low coupling ratio, while 5 pairs showed outward rectification with high coupling ratio. There was significant delay between the onset of voltage pulses in stimulating cells and the peak responses in recording cells, revealing that the gating process of gap junction channels is slow. Especially, in the outwardly rectified coupling, the activation of outward gap junction current (e.g. 6.0±2.4 msec at 0.5 V/sec ramp pulse) is slower than the deactivation (e.g. 3.1±1.8 msec at 0.5V/sec ramp pulse). The maximum coupling conductance of these channels is approximately 5.5±1.1 nS, suggesting that 10-20 gap junction channels contribute to the gap junction current between the pair of coupled MesV neurons. [Jpn J Physiol 54 Suppl:S128 (2004)]
