Reduced H3 histamine receptor binding densities in the upper layers of motor cortex in rats prone to audiogenic convulsive seizures

[Display omitted] •Histamine H3 receptor densities are reduced in the motor cortex of epileptic rats.•The decrease was specific for animals prone to audiogenic convulsive fits.•The effect is profound in the layer 2/3d of the primary motor cortex.•H3 histamine receptors might mediate the intracortical spreading of excessive excitation. Fits of audiogenic seizures in rodents are considered as a model for generalized convulsive epilepsies in humans. The laminar distribution of the H3 histamine receptor binding densities was quantified in the motor cortex of two strains of rats with genetically determined generalized epilepsies, namely KM rats with audiogenic seizures only, and WAGRij rats with both audiogenic seizures and absence seizures. It was found that H3 histamine receptor binding densities in layer 2/3d of the primary and secondary motor cortices of the rats that experienced audiogenic seizure fits were significantly lower than in the cortices of control rats. Possible explanations are discussed.