Neurones of the nucleus reticularis thalami of the rat were studied by intracellular recordings from in vitro slices. The resting membrane potential was -56.28 ± 5.86 mV (mean value ± S.D.); input resistance was 43.09 ± 9.74 MΩ; the time constant τ was 16.51 ± 3.99 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. 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. The presence of strong after-hyperpolarizing potentials (SAHP and BAHP) in RTN neurones plays a significant role in determining two different functional states, defined as tonic and oscillatory burst firing modes, respectively.
|Number of pages||12|
|Journal||Journal of Physiology|
|Publication status||Published - 1989|
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