Figure 7

HyNaCs are activated by Hydra-RFamide I. A) Representative current traces showing concentration-dependent activation of HyNaC2/3/6 and HyNaC2/9/7 by Hydra-RFamide I when oocytes had been injected with EGTA. Dashed lines represent the zero current level. B) When oocytes had not been injected with EGTA, Hydra-RFamide I elicited biphasic currents; an oocyte expressing HyNaC2/9/7 is shown as an example. C) Concentration-response curves for HyNaCs and Hydra-RFamide I. Currents were normalized to the currents at the highest agonist concentration, which had amplitudes of 9.2 ± 1.9 μA (n = 9; 2/3/5), 2.6 ± 0.4 μA (n = 12; 2/11/5), 15.7 ± 3.2 μA (n = 8; 2/3/6), 10.1 ± 1.7 μA (n = 12; 2/4/6), 19.6 ± 1.8 μA (n = 10; 2/3/7), 7.2 ± 0.9 μA (n = 10; 2/9/7) and 10.6 ± 1.8 μA (n = 8; 2/10/7), respectively. Lines represent fits to the Hill equation. D) I/V curves for putative physiological HyNaCs, revealing slightly positive reversal potentials. Voltage ramps were run from -100 mV to +30 mV in two seconds. Background currents had been subtracted by voltage ramps in the absence of agonist. Currents were normalized to the current at -100 mV. EGTA, ethylene glycol tetraacetic acid; HyNaC, Hydra Na⁺ channel.