In vivo, in vitro and computational analysis of dendritic currents in thalamic reticular neurons.
Terrence J. Sejnowski, Alain Destexhe, Diego Contreras, Mircea Steriade and John R. Huguenard

Society for Neuroscience Abstracts 21: 1187, 1995.

Thalamic reticular (RE) neurons are involved in the genesis of synchronized thalamocortical oscillations, which depend in part on their complex bursting properties. We have investigated the intrinsic bursting properties of RE cells using computational models based on morphological and electrophysiological data. Simulations of a reconstructed RE cell were compared directly to the recordings from the same cell, which allowed precise values for the passive parameters to be obtained. Voltage-clamp data were obtained on the low-threshold calcium current (ITs) in acutely dissociated RE cells which lack most of their dendrites. Simulations based on a cell with truncated dendrites and Hodgkin-Huxley kinetics reproduced these recordings with a relatively low density of ITs. In intact RE cells, high densities of ITs in distal dendrites were required to generate the higher amplitudes of the current seen experimentally, as well as the typical properties of the burst of RE cells. More importantly, we found that synaptic bombardment in the dendrites had a strong impact on the genesis of the burst, and could generate the typical burst responses of RE cells in vivo. These findings suggest that synaptic integration on the dendrites of RE cells is significantly influenced by dendritic calcium currents. In addition, we were able to simulate same behavior in simpler models with as few as three compartments, provided there was a high density of ITs in the dendrites. These experiments provide firm evidence for resolving the difference observed in the intrinsic bursting properties of RE cells in vivo and in vitro, on the basis of dendritic calcium currents.