Differential intracellular regulation of cortical GABA(A) and spinal glycine receptors in cultured neurons.
Using patch-clamp techniques we studied several aspects of intracellular GABA(A) and glycine Cl- current regulation in cortical and spinal cord neurons, respectively. Activation of PKA with a permeable analog of cyclic AMP (cAMP) produced a potentiation of the Cl- current activated with glycine, but not of the current induced with GABA. The inactive analog was without effect. Activation of PKC with 1 microM PMA reduced the amplitude of the GABA(A) and glycine currents. Internal application of 1 mM cGMP, on the other hand, had no effect on the amplitude of either current. The amplitude of these inhibitory currents changed slightly during 20 min of patch-clamp recording. Internal perfusion of the neurons with 1 microM okadaic acid, a phosphatase inhibitor, induced potentiation in both currents. The amplitude of GABA(A) and glycine currents recorded with 1 mM internal CaCl2 and 10 mM EGTA (10 nM free Ca2+) decayed by less than 30% of control. Increasing the CaCl2 concentration to 10 mM (34 microM free Ca2+) induced a transient potentiation of the GABA(A) current. A strong depression of current amplitude was found with longer times of dialysis. The glycine current, on the contrary, was unchanged by increasing the intracellular Ca2+ concentration. Activation of G proteins with internal FAl4- induced an inhibition of the GABA(A) current, but potentiated the amplitude of the strychnine-sensitive Cl- current. These results indicate that GABA(A) and glycine receptors are differentially regulated by activation of protein kinases, G proteins and Ca2+. This conclusion supports the existence of selectivity in the intracellular regulation of these two receptor types.
Tapia
J C
JC
Department of Physiology, University of Concepcion, Chile.
Espinoza
F
F
Aguayo
L G
LG
D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives; D004553:Electric Conductivity; D005459:Fluorides / Q000494:pharmacology; D007425:Intracellular Membranes / Q000502:physiology*; D051379:Mice / Q000196:embryology; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D019319:Okadaic Acid / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018009:Receptors, Glycine / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017607:Aluminum Compounds; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D019319:Okadaic Acid; C050992:tetrafluoroaluminate; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D005459:Fluorides; D002118:Calcium