Activation of substantia nigra neurons: role in the propagation of seizures in kindled rats

Abstract

The substantia nigra (SN) is crucial to the propagation of seizures in kindled rats and in other experimental seizure models. However, the mechanisms by which the SN acts to facilitate the propagation of seizures are unknown. To investigate these mechanisms we quantified the activity of SN neurons during seizures in kindled and naive rats in a paralyzed, ventilated state and examined the relationship between activity of neurons in the SN and the seizure-facilitating action of this structure. Our principal findings were that the majority of both SN dopamine and SN pars reticulata neurons, in kindled rats, fired in bursts temporally correlated to EEG waveforms recorded outside the SN during seizures; this response was only rarely found in SN neurons of naive rats during seizures elicited by stimulation of the amygdala; unlike kindled rats, lesions of the SN in naive rats did not suppress seizures. The finding that SN neurons fired in bursts during seizures in kindled, but not naive, rats indicates that seizure activity propagated into SN only in kindled rats. The correlation between seizure-suppressant effects of lesions and SN activation during seizures leads us to propose that one mechanism by which the SN promotes seizure propagation involves SN activation and transmission of seizure activity to targets of SN.

Differences in the anatomic distribution of immediate-early gene expression in amygdala and angular bundle kindling development

“…This has been demonstrated by the absence of c-fos expression in pars reticulata of substantia nigra (Labiner et al, 1993) following a kindled seizure. Unit recordings of pars reticulata neurons of substantia nigra during a class 5 kindled seizure demonstrate burst-firing (Bonhaus et al, 1986;Bonhaus et al, 1991) yet no evidence of seizure-evoked IEG expression was detected here or in our previous work (Labiner et al, 1993).…”

Ketogenic Diet Metabolites Reduce Firing in Central Neurons by Opening KATPChannels

“…The activity of SNr neurons in particular has been positively correlated with seizure activity and generalization (Bonhaus et al, 1986;Deransart et al, 2003). It is also established that suppressing the activity of these neurons can be anticonvulsant (Iadarola and Gale, 1982), although this effect depends on the site of antagonist injection and also on animal age (Velíšková and Moshé, 2006).…”

Evidence of Enhanced Kindliig and Hippocampal Neuronal Injury in Immature Rats with Neuronal Migration Disorders

“…However, subsequent seizure stages are reached with equal number of stimulations in both groups. Several studies indicated that the progression of kindling from limbic sites involves the recruitment of a paleocortical network involving pirifonn, insular, and perirhinal cortices (20)(21)(22)(23) with the eventual propagation to basal ganglia and other subcortical structures (24,25) and eventually the brainstem (18,26). The development of kindling is different in immature rats compared with adults.…”