Self–sustained rhythmic activity in the thalamic reticular nucleus mediated by depolarizing GABAA receptor potentials
Intracellular recordings from reticular thalamic (RE) neurons in vivo revealed inhibitory postsynaptic potentials (IPSPs) between RE cells that reversed and became depolarizing at the hyperpolarized membrane potentials that occur during sleep. These excitatory IPSPs can directly trigger low–threshold spikes (LTSs). The oscillatory mechanisms underlying IPSP–triggered LTSs crowned by spike bursts were investigated in models of isolated RE networks. In a one–dimensional network model, external stimulation evoked waves of excitation propagating at a constant velocity of 25–150 cells per second. In a large–scale, two–dimensional model of the reticular nucleus, the network showed transient or self–sustained oscillations controlled by the maximum conductance of the low–threshold calcium current and the membrane potential. This model predicts that the isolated reticular nucleus could initiate sequences of spindle oscillations in thalamocortical networks in vivo.