Heterogeneity of burst firing in mouse thalamic reticular nucleus neurons

The thalamic reticular nucleus (TRN) sits at the interface of the thalamus and neocortex and provides the majority of inhibition to thalamic relay nuclei. Functionally, the activity of TRN neurons can impact sensory processing and may influence arousal states. TRN neurons discharge action potentials in two distinct output modes: tonic or burst firing. Burst output, a transient high frequency discharge of action potentials, is dependent on the activation of transient low-threshold voltage-dependent T-type calcium current (IT). In our current study, we identify a broad range of burst firing frequencies in TRN neurons, which depend on the activation of IT. The amplitude of the low-threshold calcium spike (LTS) underlying the burst positively correlated with burst frequency and number of action potentials per burst. Activation of small conductance calcium-activated potassium (SK) channels on TRN neurons can impact burst discharge. Attenuation of SK channels increased TRN neuron burst frequency through an increase in LTS duration, but not magnitude. The broad range of burst firing frequencies could provide distinct downstream inhibition within thalamic nuclei.