Neocortical cytopathology in focal aminopyridine seizures as related to the intracortical diffusion of [3H] 4-aminopyridine. Electrophysiologic and light-microscopic studies.

Focal seizure was induced in rat and cat neocortex by the topical application of aminopyridines. The epileptic character of the focal events was followed by surface and intracellular recordings of seizure activity. The pathologic alterations in the neurons, the glial cells, and the protein permeability of the neocortical blood vessels were investigated by means of light microscopy, using standard histological stainings and immunohistochemical detection of endogenous serum albumin. Diffusion of [3H] 4-aminopyridine in the neocortex was studied by light-microscopic autoradiography. The spreading of the neuropathologic changes strictly followed the diffusion of the tritiated compound, suggesting the gradual involvement of neocortical layers in the seizure process.