Fig. 2. Reversal potential of I  ^hin thalamocortical relay neurons. (A ) Current responses (I ) to 500-ms voltage pulses injected in 10-mV increments (E ) of a neuron held at potentials (V  ^h) of −68 mV and −88 mV, respectively. Recordings were conducted in the presence of extracellular Ba²⁺(0.1 mM BaCl²) to block the inwardly rectifying K⁺current, I  ^Kir. The voltage-current relationships of the instantaneous current at the beginning of each pulse (I  ^inst, Fig. 1A; arrows ) were determined at both potentials. (B ) The I  ^instvoltage-current data (n = 5 neurons) were fit with linear regression and the I  ^hreversal potential (V  ^r) was estimated from the intersection of the two regression lines.