The prefrontal cortex shows widespread decrease in H3 histamine receptor binding densities in rats with genetic generalized epilepsies

Distributions of brain H3 histamine receptors in regions of the prefrontal cortex were studied by assessing regional binding densities for [3 H](R)α-methylhistamine in coronal brain slices of normal rats and rats with genetically determined absence and/or audiogenic epilepsies. The three groups of epileptic rats displayed widespread significant decreases in H3 histamine receptor binding densities. A 20-25% decline was seen in the rostral aspects of the lateral prefrontal cortex, namely the granular, dysgranular, and dorsal agranular insular regions. The reduction was not specific for the epilepsy types. The same was observed in the rostral part of the primary cingulate cortex and the secondary midcingulate cortex. On borders of this core effect, several seizure-type specific declines were seen. Namely, the infralimbic, prelimbic and posterior agranular insular cortices demonstrated absence-epilepsy related reductions in the H3 histamine receptor binding densities. A decrease related to audiogenic seizures was noted in the rostral part of the piriform cortex. The pattern of widespread and seizure-type unspecific decline in H3 histamine receptor binding densities points to a common part of brain loops underlying generalized convulsive and non-convulsive types of epilepsy. It also might hint at putative seizure-related changes in the release of histamine from specific fibers innervating the prefrontal area.