Fig. 7.
ATP inhibits CaV2.2 channels in muscle afferent neurons. All currents were recorded in 10 mM Ca2+. A: the inhibition of CaV current induced by 10 μM ATP (black trace) compared with Cntl (gray trace) recorded from a muscle afferent neuron. The inhibition is transiently reversed by strong depolarization (+80 mV), which can be seen by comparing the prepulse (before the +80-mV step) and postpulse (following the +80-mV step) currents. B: there was no clear differences in ATP (10 μM) induced inhibition in small (<30 μm) vs. medium (30–40 μm) vs. large (>40 μm) muscle afferent neurons. The percent inhibition of prepulse current measured from 13 muscle afferent neurons is plotted vs. neuron diameter. C: the ATP (10 μM) inhibition is blocked by preapplication of 10 μM GVIA. This time course shows the inhibition induced by ATP prior to GVIA application and little or no ATP response in the presence of GVIA. The prepulse (solid circle) and postpulse (open circle) current amplitudes are plotted. D: the average (±SD) inhibition induced by 10 μM ATP is shown before (ATP) and during (GVIA + ATP) application of 10 μM GVIA. *ATP response in GVIA is significantly different from that in Cntl. The number of muscle afferent neurons tested is indicated.