Mechanotransduction of trigeminal ganglion neurons innervating inner walls of rat anterior eye chambers

Abstract

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