Intrinsic properties of nucleus reticularis thalami neurones of the rat studied in vitro.

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Abstract
1. Neurones of the nucleus reticularis thalami of the rat studied by intracellular recordings from in vitro slices. The resting membrane potential was -56.cntdot.28.+-.5.cntdot.86 mV (mean value.+-.S.D.); input resistance was 43.cntdot.09.+-.9.cntdot.74 M.OMEGA.; the time constant .tau. was 16.cntdot.51.+-.3.cntdot.99 ms. At the resting membrane potential tonic firing is present, while at membrane potentials more negative than -60 mV a burst firing mode gradually prevails. 2. Prolonged depolarizing current pulses superimposed on a steady hyperpolarization consistently activated sequences of burst-after-hyperpolarization complexes. The all-or-none burst response consisted of Na+-mediated, TTX-sensitive fast action potentials superimposed on a low threshold spike (LTS). The burst was followed by a stereotyped after-hyperpolarization lasting 100-120 ms (BAHP), with a maxima -85 mV. The BAHP was blocked by Cd2+ and apamine but not by 8-Br cyclic AMP. The early component of BAHP was significantly attenuated by TEA. The oscillatory rhythmic discharges were abolished by agents which blocked the BAHP. 3. The presence of strong after-hyperpolarizing potentials (SAHP and BAHP) in TNR neurones plays a significant role in determining two different functional states, defined as tonic and oscillatory burst firing modes, respectively.