Rhythmic oscillations throughout the cortex are observed during physiological and pathological states of the brain. The thalamus generates sleep spindle oscillations and spike-wave discharges characteristic of absence epilepsy. Much has been learned regarding the mechanisms underlying these oscillations from in vitro brain slice preparations. One widely used model to understand the epileptiform oscillations underlying absence epilepsy involves application of bicuculline methiodide (BMI) to brain slices containing the thalamus. BMI is a well known GABA_A receptor blocker that has previously been discovered to also block SK channels (Debarbieux et al. 1998). Here we report that the robust epileptiform oscillations observed during BMI application rely synergistically on both GABA_A receptor and SK channel antagonism. Neither application of picrotoxin, a selective GABA_A receptor antagonist, nor application of apamin, a selective SK channel antagonist, alone yielded the highly synchronized, long-lasting oscillations comparable to those observed during BMI application. However, partial blockade of SK channels by sub-nanomolar concentrations of apamin combined with picrotoxin sufficiently replicated BMI oscillations. We found that at the cellular level apamin enhanced the intrinsic excitability of RT neurons but had no effect on relay neurons. This work suggests that regulation of RT excitability by SK channels can influence the excitability of thalamocortical networks and may illuminate possible pharmacological treatments for absence epilepsy. Finally, our results suggest that changes in the intrinsic properties of individual neurons and changes at the circuit level can robustly modulate these oscillations.