Ichinohe Sho, Ishii Toshiyuki, Takahashi Hiroshi, Kaneda Makoto
Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
Neurosci Res. 2017 Feb;115:5-12. doi: 10.1016/j.neures.2016.09.012. Epub 2016 Oct 5.
ATP activates P2X receptors and acts as a neurotransmitter in the nervous system. We have previously reported that P2X receptors modulate the firing rate of retinal ganglion cells. Since many subtypes of P2X receptors are distributed in the mouse retina, it is likely that the modulatory effects of P2X receptor-mediated signaling can occur at multiple synaptic levels in the retina. In this study, we investigated whether P2X receptors expressed between the photoreceptor layer and the inner nuclear layer in the mouse retina were physiologically functional, by electroretinography (ERG). In the combined rod-cone ERG and the scotopic ERG, intravitreal injection of PPADS, an antagonist of P2X receptors, had no effects on the amplitude of the a-wave, but decreased the amplitude of the b-wave. In the photopic ERG, intravitreal injection of PPADS significantly decreased the amplitude of both the a-wave and the b-wave. In ex vivo recordings, a decrease in the b-wave amplitude was observed at 20μM PPADS, confirming that the inhibition of the b-wave by intravitreal injection of PPADS is due to the inhibition of P2X receptors. Our findings suggest that P2X receptor-mediated signaling has a physiological effect in both the rod and the cone pathways in postreceptoral processing.
三磷酸腺苷（ATP）激活P2X受体，并在神经系统中作为神经递质发挥作用。我们之前曾报道，P2X受体可调节视网膜神经节细胞的放电频率。由于P2X受体的许多亚型分布于小鼠视网膜中，P2X受体介导的信号传导的调节作用很可能在视网膜的多个突触水平上发生。在本研究中，我们通过视网膜电图（ERG）研究了小鼠视网膜中光感受器层和内核层之间表达的P2X受体是否具有生理功能。在联合视杆-视锥ERG和暗视ERG中，玻璃体内注射P2X受体拮抗剂吡哆醛-5'-磷酸硫酸酯（PPADS）对a波振幅没有影响，但降低了b波振幅。在明视ERG中，玻璃体内注射PPADS显著降低了a波和b波的振幅。在离体记录中，在20μM PPADS时观察到b波振幅降低，证实玻璃体内注射PPADS对b波的抑制作用是由于对P2X受体的抑制。我们的研究结果表明，P2X受体介导的信号传导在感受器后处理的视杆和视锥通路中均具有生理作用。
