Philanthotoxins block glutamatergic transmission in rat hippocampus--II. Inhibition of synaptic transmission in the CA1 region.
1. Philanthotoxins decrease the amplitude of the population spike (PS), the field excitatory postsynaptic potential (f-EPSP), and the presynaptic volley (PV), as evoked by Shaffer-collateral-commisural inputs to the CA1 pyramidal cells in the rat hippocampus slice. 2. The effects are slow and often not completely reversible. 3. Dideaza-philanthotoxin-12 is, in all experiments, the most active antagonist showing a very poor recovery. 4. Using a twin pulse the percentual decreases of f-EPSP and PV amplitudes are almost identical for the first and second response. However, the first PS is much more affected than the second one, indicating a possible effect on the inhibiting circuit. 5. Philanthotoxins cause a non-competitive inhibition. 6. Besides a possible postsynaptic block and a distinct presynaptic effect (preceding paper) a non-postsynaptic effect (on the PV) is described.
Department of Pharmacology, Amsterdam, The Netherlands.
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Schluter
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Piek
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Lopes da Silva
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists; D005260:Female; D005971:Glutamates / Q000502:physiology*; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects*; D066298:In Vitro Techniques; D015394:Molecular Structure; D011073:Polyamines; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D014862:Wasp Venoms / Q000494:pharmacology*
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D011073:Polyamines; D014862:Wasp Venoms; D018698:Glutamic Acid; C034092:delta-philanthotoxin