Bursting and tonic discharges in two classes of reticular thalamic neurons

Abstract

1. Two types of cat reticular (RE) thalamic cells were disclosed by means of intracellular recordings under urethan anesthesia. The RE neurons were identified by their typical depolarizing spindle oscillations in response to synchronous stimulation of the internal capsule. 2. In type I neurons (n = 41), depolarizing current pulses induced tonic firing at the resting or slightly depolarized membrane potential (Vm) and triggered high-frequency spike bursts at a Vm more negative than -75 mV. As well, these cells discharged rebound bursts at the break of a hyperpolarizing current pulse. Internal capsule stimulation elicited spindle sequences made off by depolarizing waves giving rise to spike bursts. 3. Type II cells (n = 9) did not discharge spike bursts to large depolarizing current pulses even when the Vm reached -100 mV, nor did they fire rebound bursts after long-lasting hyperpolarizing current pulses or spike bursts riding on the rhythmic depolarizing components of spindle sequences. 4. Compared with type I cells, type II cells showed less frequency accommodation during tonic firing. The latter neuronal class discharged at high frequencies (40 Hz) with slight DC depolarization, approximately 8-10 Hz at the resting Vm, and no underlying synaptic or subthreshold oscillatory events could be detected when the firing was blocked by DC hyperpolarization. 5. The presence of two cell classes in the RE nucleus challenges the common view that this nucleus consists of a single neuronal class. We suggest that a different set of conductances is present in type II RE neurons, thus preventing the low-threshold Ca2+ current from dominating the behavior of these cells.

Optogenetically induced sleep spindle rhythms alter sleep architectures in mice

“…1B. However, this was not always observed, as reported previously (21,22).Illumination evoked photocurrents in ChR2-positive TRN neurons (Fig. 1C).…”

The calcium-binding protein parvalbumin modulates the firing 1 properties of the reticular thalamic nucleus bursting neurons

“…The tonically firing neurons represent the smallest population in the mouse RTN as observed also in the cat and in rat (Contreras et al 1992;Domich et al 1986;Lee et al 2007;Villa 1990). Interestingly, we found only four cells characterized by an oscillatory firing pattern in WT and none in PVKO mice.…”

“…There is ample evidence that mutations in (or ablation of) Ca 2ϩ signaling components in neurons lead to changes in the remaining ones with respect to expression levels, localization, and even change in cell morphology, e.g., of organelles implicated in Ca 2ϩ signaling (Schwaller 2012). Most RTN neurons fire with a characteristic bursting discharge pattern, but a subpopulation of RTN neurons has been reported to fire tonically (Contreras et al 1992;Lee et al 2007;Villa 1990). These electrophysiological observations are in agreement with the morphological observation of the presence of several neuronal subtypes in the RTN (Clemence and Mitrofanis 1992;Houser et al 1980;Jones 1975;Lubke 1993;Scheibel and Scheibel 1966;Yen et al 1985).…”

Global Intracellular Slow-Wave Dynamics of the Thalamocortical System

“…Van Horn and Sherman, 2007), the activities of modulators were much more pronounced within higher-order nuclei than within sensory VPM and LGN nuclei. (3) It appears that the RTN provides a stronger inhibition into sensory thalamic nuclei during cortical active states than the ZI onto higher-order nuclei because a majority of RTN neurons fire bursts of action potentials (Avanzini et al, 1989;Contreras et al, 1992;Fuentealba et al, 2005), but ZI neurons fire tonically (Trageser et al, 2006). Therefore, the postsynaptic action of RTN neurons should be stronger compared with ZI neurons.…”