Focal penicillin seizures--motor activity and cellular physiology and morphology.

Two types of intracellular activity have been found in neurons in the cortical penicillin seizure focus during an interictal spike; a prolonged depolarization (PDS) followed by hyperpolarization or predominantly hyperpolarization. In the present study of a penicillin focus we have correlated the penicillin focus location with motor behavior and the cellular physiology with cellular morphology and location. Penicillin injection at the same location in the anterior sigmoid gyrus invariably resulted in focal seizures involving the contralateral shoulder. From the locations of the myoclonus and the focus, the character of the movements and the route of seizure spread we conclude that the same pathways mediate movement produced by penicillin seizures or by electrically stimulating the same motor cortex. Intracellular recordings and dye-marking of cells in and around the seizure focus revealed that PDS neurons were located within a 3 mm radius from the site of penicillin injection. All PDS neurons either lacked well filled processes or had abnormal dendrites. Inhibited neurons were all pyramidal neurons with normal dendrites. The dendritic abnormalities observed could be important in the genesis of the PDS.

Cholecystokinin in hippocampal pathways.

The distribution of cholecystokininlike (CCK-L) immunoreactive cells and fibers in the rat hippocampal formation and its afferent and efferent connections was studied using the immunoperoxidase technique. In the hippocampal formation CCK-L immunoreactive perikarya were located in the polymorphic zone of the dentate hilus, all layers of Ammon's horn, the subiculum, the presubiculum, and the entorhinal cortex. Cholecystokininlike immunoreactive fibers extended from cell bodies or were located around the cell bodies in the entorhinal cortex, subiculum and stratum pyramidale of Ammon's horn, and among the granule cells and inner molecular layer of the dentate gyrus. The immunoreactive cells in the stratum oriens may be a type of basket cell, since processes from these cells extend into stratum pyramidale and collections of CCK-L immunoreactive fibers are seen around cell bodies in stratum pyramidale. Cholecystokininlike immunoreactive fibers were also observed in the alveus, ventral and lateral fimbria, and ventrolateral lateral septal nucleus. Some of these immunoreactive fibers, therefore, being to either an efferent or afferent hippocampal pathway(s) originating from CCK-L immunoreactive pyramidal cells in the hippocampal formation and/or from the hippocampal subcortical nuclei, the supramammillary nucleus, and the dorsomedial hypothalamic nucleus which contain CCK-L immunoreactive perikarya. The distribution of these immunoreactive fibers in the fimbria and lateral septal nucleus is most consistent with an anteriorly directed efferent hippocampal pathway.