Figure 3
From: ATP signaling in the integrative neural center of Aplysia californica
Functional expression of recombinant AcP2X receptors in Xenopus oocytes. (A) Examples of currents recorded in response to different concentrations of ATP (HP = − 70 mV, agonist application indicated by the solid line). (B) Dose–response curves for ATP receptor activation. Mean currents were normalized to the response given by 250 μM ATP (n = 7, oocytes). Serially increasing concentrations of ATP were applied to oocytes for 15 s at 6-min intervals. Symbols represent mean ± S.E. Continuous line for ATP represents data fitted using the equation I = Imax/[1 + (IC50/L)nH], where I is the actual current for a ligand concentration (L), nH is the Hill coefficient, and Imax is the maximal current (IC50fast = 306.0 μM, IC50slow = 497.4 μM; nHfast = 1.58, nHslow = 0.97). C. Two-electrode voltage-clamp recordings from oocytes expressing AcP2X receptors. Representative inward currents recorded in response to ATP (red trace) and the 250 μM of Bz-ATP (HP = − 70 mV, application indicated by the solid line) (n = 8, oocytes). (D) Recordings of ATP-induced current (250 μM, ATP) in the presence of normal [Na+] (96 mM) and with elevated extracellular Na+ (144 mM; red trace); HP = -70 mV(n = 6, oocytes). (E) Ramp voltage-clamp protocol from − 70 mV HP to 20 mV in the presence of 250 μM ATP. The plots of the subtracted current (a current in the presence of ATP minus the current in the absence of ATP) against voltage during the ramp. The red trace—high [Na+], 144 mM. According to the Nernst equation, the reversal potential was shifted by 10.2 ± 1.3 mV to the + direction of the holding potential (n = 6, oocytes).
