Mechanotransduction of Trigeminal Ganglion Neurons

23 To address mechanoreceptive roles of trigeminal ganglion (TG) nerve endings in the 24 inner walls of rat anterior eye chambers, we investigated the mechanotransduction 25 process and mechanosensitive (MS) channel on somata of TG neurons innervating this 26 area in vitro. Rat TG neurons innervating inner walls of anterior chambers were labeled 27 by anterior chamber injection of 1,1'-Dilinoleyl-3,3,3',3'-Tetramethylindocarbocyanine, 28 4-Chlorobenzenesulfona (FAST DiI). The neuronal cell bodies were voltage clamped 29 using whole-cell patch-clamp techniques, while it was deformed by ejection of bath 30 solution to verify mechanotransduction. Immunofluorescence staining was performed on 31 the sections of TG ganglia to determine the specific MS channel proteins. Mechanical 32 stimuli induced MS currents in 55 out of 96 FAST DiI-labeled TG neurons. The MS 33 currents exhibited characteristics of mechanical intensity-dependent and clamp voltage34 dependent. Mechanical stimulation further enhanced the membrane potential and 35 increased the frequency of action potentials. Transient receptor potential ankyrin 1 36 (TRPA1), TRP vanilloid 4 (TRPV4), acid-sensing ion channel (ASIC) 2 and ASIC3 37 channel proteins were expressed in FAST DiI-labeled TG neurons. The inhibitory effect 38 of HC-030031, a specific inhibitor of TRPA1 on MS currents demonstrated that TRPA1 39 was an essential MS channel protein. Taken together, our results show that mechanical 40 stimuli induce MS currents via MS channels such as TRPA1 to trigger 41 mechanotransduction in TG neurons innervating inner walls of anterior chambers. Our 42 results indicate the existence of mechanoreceptive TG nerve endings in inner walls of 43 anterior chambers. Whether the mechanoreceptive TG nerve endings play a role in 44 intraocular pressure sensation warrants further investigation. 45 46