Parenteral penicillin in rats: an experimental model of multifocal epilepsy.

Parenterally injected penicillin in rats induces a peculiar pattern of multifocal epilepsy. The effective amount is higher than that required in cats. The epileptiform activity initially appears on the cortical mantle of one hemisphere; after a variable delay, contralateral cortical spikes arise in a completely asynchronous way. Spontaneous independent firing is observed, with a further delay in subcortical structures. Although cortical spiking shows a tendency to become bilaterally synchronous, such synchrony has been only occasionally observed between the various subcortical structures. Formation of generalized spike-and-wave complexes, as reported in cats, or other features reminiscent of the human petit mal did not occur. This study stresses the differences in pathophysiological responses to the same epileptogenic model according to species variation.