The convulsant effects of kainic acid microinjections into cerebral cortex are concentration but not laminar dependent.
The direct excitatory glutamate analog, kainic acid, when injected into different layers of the cat visual cortex, has two effects on this tissue that are fundamentally different from those exerted by the disinhibitory agents penicillin, bicuculline, and strychnine. First, both concentration-dependent suppression and convulsant activity was seen. Second, these concentration-dependent influences were produced effectively in each cortical layer challenged despite a reported preferential localization of kainic acid receptors to layer 6. In contrast, the disinhibitory agents generally produce only convulsant effects, do so in a laminar-specific manner, and at significantly lower concentrations in intact brain (i.e., 50 microM vs 15 mM). These results suggest that kainic acid, in the concentrations employed here, has a generalized excitatory effect on all cortical circuitry and that it's convulsant influences are nonspecific and less potent than those of the inhibitory blockers. Further, a common neural trait shared by these different modes of epileptogenesis is discussed.
Chatt
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AB
Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510.
Ebersole
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JS
D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D005074:Evoked Potentials, Visual; D007608:Kainic Acid; D008845:Microinjections; D009994:Osmolar Concentration; D012640:Seizures / Q000139:chemically induced* / Q000503:physiopathology; D014793:Visual Cortex / Q000502:physiology*
D007608:Kainic Acid