Immunohistochemistry of cerebellar seizures: mossy fiber afferents play an important role in seizure spread and initiation in the rat

Non-competitive antagonists of NMDA and AMPA receptors decrease seizure-induced c-fos protein expression in the cerebellum and protect against seizure symptoms in adult rats

The aim of the present study was to examine the role of ionotropic glutamate receptors in the cerebellum during generalized seizures. Epileptic neuronal activation was evaluated through the immunohistochemical detection of c-fos protein in the cerebellar cortex. Generalized seizures were precipitated by the intraperitoneal injection of 4-aminopyridine. The animals were pretreated with the NMDA receptor antagonists MK-801 (2 mg/kg), amantadine (50 mg/kg), and the AMPA receptor antagonist GYKI 52466 hydrochloride (50 mg/kg). Two hours after 4-aminopyridine injection, the number of c-fos immunostained cell nuclei was counted in serial immunohistochemical sections of the cerebellar vermis. The number of c-fos immunostained cell nuclei in the granular layer decreased significantly in animals pretreated with the glutamate receptor antagonists compared to the untreated animals having convulsion. We can conclude that mossy fiber stimulation exerts its seizure-generating action mainly through the ionotropic glutamate receptors of the mossy fiber synapses. Both NMDA and AMPA receptor antagonists are effective in reducing glutamate-mediated postsynaptic effects in the cerebellar cortex.

Lesional cerebellar epilepsy: a review of the evidence

Classical teaching in epileptology localizes the origins of focal seizures solely in the cerebral cortex, with only inhibitory effects attributed to subcortical structures. However, electrophysiological and neuroimaging studies over the last decades now provide evidence for an initiation of epileptic seizures within subcortical structures. Intrinsic epileptogenicity of hypothalamic hamartoma has already been established in recognition of subcortical epilepsy, whereas a seizure-generating impact of dysplastic cerebellar lesions remains to be clarified. Herein, we examine the supportive evidence and clinical presentation of cerebellar seizures and review therapy options.