| 9374187 |
Tapia JC, Espinoza F, Aguayo LG: Differential intracellular regulation of cortical GABA (A) and spinal glycine receptors in cultured neurons. Brain Res. 1997 Sep 26;769(2):203-10.
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. |
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