title: Timing of the developmental switch in GABA(A) mediated signaling from excitation to inhibition in CA3 rat hippocampus using gramicidin perforated patch and extracellular recordings.
abstract: The timing of the developmental switch in the GABA(A) mediated responses from excitatory to inhibitory was studied in Wistar rat CA3 hippocampal pyramidal cells using gramicidin perforated patch-clamp and extracellular recordings. Gramicidin perforated patch recordings revealed a gradual developmental shift in the reversal potential of synaptic and isoguvacine-induced GABA(A) mediated responses from -55 +/- 4 mV at postnatal days P0-2 to -74 +/- 3 mV at P13-15 with a midpoint of disappearance of the excitatory effects of GABA at around P8. Extracellular recordings in CA3 pyramidal cell layer revealed that the effect of isoguvacine on multiple unit activity (MUA) switched from an increase to a decrease at around P10. The effect of synaptic GABA(A) mediated responses on MUA switched from an increase to a decrease at around P8. It is concluded that the developmental switch in the action of GABA via GABA(A) receptors from excitatory to inhibitory occurs in Wistar rat CA3 pyramidal cells at around P8-10, an age that coincides with the transition from immature to mature hippocampal rhythms. We propose that excitatory GABA contributes to enhanced excitability and ictogenesis in the neonatal rat hippocampus.
authors.affiliation: INMED/Inserm U29, 163, Marseille, France.
authors.forename: Roman
authors.initials: R
authors.lastname: Tyzio
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Holmes
authors.forename: Yehezkiel
authors.initials: Y
authors.lastname: Ben-Ari
authors.forename: Roustem
authors.initials: R
authors.lastname: Khazipov
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001640:Bicuculline / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D058787:GABA-A Receptor Antagonists; D006096:Gramicidin; D006624:Hippocampus / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D007539:Isonicotinic Acids / Q000494:pharmacology; D008297:Male; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D058787:GABA-A Receptor Antagonists; D007539:Isonicotinic Acids; D011963:Receptors, GABA-A; D006096:Gramicidin; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline; C015300:isoguvacine