Fig. 9. Activity of NRT neurons recorded intracellularly with KCl-filled electrodes. A1, Compared with the recordings with KAc electrodes (Fig. 5), NRT neurons recorded with KCl electrodes had a more depolarized resting membrane potential (arrow) and a much stronger background firing (B). During SWDs, the bursts of action potentials (C) had a lower frequency than those observed with KAc electrodes. Marked periods are enlarged in B,C, D1, and E1 below.A2, Schematic horizontal plane drawing showing the position (filled circle) of the NRT neuron from which the activity in A1 was recorded.AM, Anteromedial thalamic nucleus; AV, anteroventral thalamic nucleus; nRT, thalamic reticular nucleus; VL, ventrolateral thalamic nucleus;VM, ventromedial thalamic nucleus (anteriority relative to the interaural line is indicated). A3, Photomicrograph of the neurobiotin-injected NRT neuron inA2. Note the typical fusiform perikaryon and numerous varicose dendrites. D1, D2, Hyperpolarization (arrowheads) could be detected at the start of a SWD during recordings with KCl electrodes, both at resting (D1) and hyperpolarized (D2) (−1.3 nA) membrane potentials. The smaller size of the hyperpolarization at potentials greater than −60 mV was not peculiar to KCl recordings.E1–E3, LTCPs and associated bursts of action potentials recorded during SWD at resting membrane potential (E1) and at two hyperpolarized levels achieved by injection of −0.5 nA (E2) and −1.3 nA (E3) (membrane potential before the SWDs is indicated by an arrow). As in KAc recordings (Fig. 8), the LTCPs become larger in amplitude with steady hyperpolarization. The resting membrane potential indicated in B (arrow) also applies toC and D1. Dashed lines inE1–E3 correspond to the indicated membrane potentials. Voltage calibration in D2 also applies toB, C, and D1. Time calibration in C and D2 also applies toB and D1, respectively. Calibrations inE3 also apply to E1 andE2.