Inhibitory interconnections control burst pattern and emergent network synchrony in reticular thalamus

Inhibitory connections between neurons of the thalamic reticular (RE) nucleus are thought to help prevent spike-wave discharge (SWD), characteristic of generalized absence epilepsy, in thalamic and thalamocortical circuits. Indeed, oscillations in thalamic slices resemble SWD when intra-RE inhibition is blocked and are suppressed when intra-RE inhibition is enhanced. To elucidate the cellular mechanisms underlying these network changes, we recorded from RE cells during oscillations in thalamic slices and either blocked intra-RE inhibition with picrotoxin or enhanced it with clonazepam. We found that intra-RE inhibition limits the number and synchrony, but not the duration, of RE cell bursts. We then performed simulations that demonstrate how inhibition can shift network activity into a desynchronized mode simply by vetoing occasional RE cell bursts. In contrast, when intra-RE inhibition is blocked, RE cells burst synchronously, enabling even short RE cell bursts to promote epileptogenesis in two ways: first, by activating GABA(B) receptors, and second, through the GABA(B) receptor-independent emergence of network synchrony.