Fig. 5. Activating TRPV4 enhances membrane excitability of parasol ganglion cells.

Na currents (I_Na) mediated by voltage-gated Na channels were recorded under whole-cell voltage-clamp mode from flat mount retinas. Electric pulses were used to hold the membrane potential from a baseline level of −110 mV (b and c) or −70 mV (d) to a series of Vh. The I_Na is activated at Vh ≈ −50 mV (c). The application of TRPV4 agonist 4αPDD 1 μM in the bath does not clearly alter the activation curve (c) or peak amplitude of I_Na (b), while the delay time (T) of I_Na is shortened for all suprathreshold stimuli (d). The relationship of T and Vh is significantly altered (p < 0.05 for both T and τ) (For definitions of τ see methods). In a, the arrow depicts the axon, and the scale bar is 20 μm. The chloride equilibrium potential is −61 mV. Vh-holding potential