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Persistent depolarizing action of GABA in rat Cajal‐Retzius cells
Author(s) -
Mienville JeanMarc
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.809bd.x
Subject(s) - depolarization , muscimol , gabaa receptor , neocortex , inhibitory postsynaptic potential , chemistry , membrane potential , neuroscience , reversal potential , biophysics , electrophysiology , gamma aminobutyric acid , hippocampal formation , gabaergic , patch clamp , biology , receptor , biochemistry
1 To characterize membrane properties that might be relevant to the function and fate of Cajal‐Retzius (CR) cells, the pharmacological and physiological effects of GABA acting at GABA A receptors were studied in CR cells from embryonic (E18) and postnatal (P11–13) slices of rat neocortex. 2 From the embryonic to the postnatal stage, GABA‐induced maximum current almost tripled, the EC 50 increased from 38 to 74 μ m , and the Hill number increased from 1.4 to 1.9. Muscimol‐elicited currents were qualitatively and quantitatively similar to those produced by GABA. 3 GABA‐induced changes in the amplitude of large‐conductance Ca 2+ ‐activated K + channel current recorded on‐cell from E18 CR cells were consistent with depolarization. 4 GABA‐mediated depolarization of embryonic and postnatal CR cells was studied directly with perforated‐patch recording techniques. Ten micromolar and 1 m m GABA, respectively, depolarized E18 CR cells to −27 ± 1 and −25 ± 3 mV. These same concentrations of GABA depolarized P11 CR cells to −36 ± 3 and −23 ± 3 mV. 5 In postnatal cortex, GABA (100 μ m ) increased the firing rate of CR cells 7.3‐fold. By contrast, the firing of hippocampal pyramidal cells from slices of the same age (P12) was totally and reversibly blocked by GABA. 6 These experiments suggest that contrary to its postnatal inhibitory shift observed in other cells, the depolarizing effect of GABA remains in CR cells from E18 until their virtual disappearance.