Kainic acid and penicillin: differential effects on excitatory and inhibitory interactions in the CA1 region of the hippocampal slice.
The effects of kainic acid (KA, 0.05-1.0 microM), and penicillin (PN, 3.4 mM) were studied in the CA1 region of rat hippocampal slices. Three components of the overall input/output function were taken: (1) the amplitude of the presynaptic compound action potential (prevolley) vs stimulation current applied to Schaffer collaterals, (2) the magnitude of the focally recorded synaptic potential (population EPSP) vs prevolley amplitude; and (3) the amplitude of the focally recorded population spike vs population EPSP magnitude. Recurrent inhibition was measured using the antidromic-orthodromic paired pulse method. KA caused a significant and reversible enhancement of all 3 component input/output functions while having no effect on paired pulse inhibition. PN caused a left shift in the EPSP-population spike relationship and decreased or abolished paired pulse inhibition; the other two measures of excitability were not changed. These results suggest that PN and KA differ fundamentally in the mechanisms by which they produce seizures: PN by removing inhibition while not affecting neuronal excitability per se; KA by exerting a generalized excitatory effect on neural membranes and on synaptic function while leaving recurrent inhibition unchanged.
D000818:Animals; D003292:Convulsants / Q000494:pharmacology*; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D006624:Hippocampus / Q000187:drug effects*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D010406:Penicillins / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D003292:Convulsants; D010406:Penicillins; D011759:Pyrrolidines; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D007608:Kainic Acid