Ventromedial thalamic lesions and seizure susceptibility.

Recent data indicate that the substantia nigra is an important site in a circuitry involved in the modification of various experimental seizures with neocortical and limbic involvement. Since there are no direct nigral projections to either area, we assumed that the nigral effects on seizures are relayed by other sites such as the thalamus. To evaluate this hypothesis we produced bilateral high-radiofrequency thermocoagulative lesions of the ventromedial (VM) thalamic nuclei which receive the nigral efferents in the rat. We determined the susceptibility of lesioned and control adult rats to the development of flurothyl seizures 2 and 4 weeks later. The latency to the onset of a generalized seizure was considered as the convulsive threshold. There were no differences in the mean latencies between the groups. The results suggest that bilateral destruction of the VM thalamic nuclei does not modify the susceptibility to the development of flurothyl seizures in the rat.