A specific 70K protein found in epileptic rat cortex: induction of bursting activity and negative resistance by its intracellular application in Euhadra neurons

• Published in: Journal of neurobiology Vol. 22; no. 3; p. 287
• Main Authors: Onozuka, M, Imai, S, Furuichi, H, Ozono, S
• Format: Journal Article
• Language: English
• Published: United States 01.04.1991
• Subjects: Animals; Antibodies, Anti-Idiotypic - immunology; Antibody Specificity; Calcium - metabolism; Cerebral Cortex - metabolism; Electrophoresis, Polyacrylamide Gel; Electrophysiology; Epilepsy - metabolism; Microelectrodes; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - pharmacology; Neurons - drug effects; Neurons - metabolism; Phenytoin - pharmacology; Rats; Rats, Inbred Strains; Snails - metabolism; Sodium - metabolism; Veratridine - pharmacology
• ISSN: 0022-3034
• DOI: 10.1002/neu.480220308

The effect of 70-kD protein (P70, a specific protein found in cobalt-induced epileptogenic focus of rat cerebral cortex) on membrane properties was examined in identified neurons of the snail, Euhadra peliomphala, using the pressure injection method combined with the voltage-clamp technique. In neurons that normally exhibited spontaneous regular firing, intracellular injection of P70 elicited bursting activity and a negative slope resistance (NSR) region in their current-voltage (I-V) curve in a manner corresponding to the duration of its injection. These responses were suppressed by prior injection of an antibody to P70 into the neurons, and were markedly inhibited by a reduction of extracellular Na+ ions and the anticonvulsant agent phenytoin, but not by Co(2+)-substituted Ca(2+)-free saline. In addition, intracellularly applied P70 potentiated both bursting activity and the NSR induced by a Na channel activator, veratridine. However, prior application of a saturating dose of this activator occluded the effect of P70. These results suggest that P70 elicits a Na(+)-dependent negative resistance, which may contribute to the generation of bursting activity.