The results of penicillin G Administration of chronic unrestrained cats: electrographic and behavioral observations.

Intramuscular administration of penicillin G was carried out in a series of 27 chronic cat preparations. In addition to the EEG, the high frequency components of cerebral electrical activity were also recorded from cortical and deep structures. Videotape recordings using split-screen technique allowed correlations of the animal's clinical state with the EEG. The results showed that 'spike-wave' type activity occurred earliest in the cortex. The discharges were also best formed in cortical and thalamic structures. The other deep structures showed characteristic bursting, but not of the 'spikewave' type variety. The cerebellum showed also early participation. Clinical expressivity of the bursts depended upon the state of alertness of the animal, the height of the spike components and the extent of depth participation. The high frequency recordings revealed characteristic alternation of decrease and increase in activity mostly in cortical structures and to a lesser extent in thalamus. Pontine and medullary reticular formation areas showed usually no changes in the high frequency records during the bursts. When major seizures were induced, they were always of focal onset rather than of the primary generalized type as one sees with pentylenetetrazol. Different cortical or deep structures served as the initiating site in different animals. It was concluded that systemic penicillin adminstration does not lead to a truly primary generalized form of epilepsy, but produces its effects by multifocal activation of various cerebral structures, with cortex and cerebullum usually showing earliest involvement.