An intracellular analysis of gamma‐aminobutyric‐acid‐associated ion movements in rat sympathetic neurones.

Abstract

SUMMARY1. Double-barfelled ion-sensitive micro-electrodes were used to measure the changes of the intracellular activities of Cl-, K+, and Na+ (at1, ak, aka) in neurons of isolated rat sympathetic ganglia during the action of y-aminobutyric acid (GABA).2. The membrane potential of some of the neurones was manually 'voltage clamped' by passing current through the reference barrel of the ion-sensitive micro-electrode. This enabled us to convert the normal depolarizing action of GABA into a hyperpolarization.3. A GABA-induced membrane depolarization was accompanied by a decrease of at1, ai and no change in ai whereas a GABA-induced membrane hyperpolarization noK Na' a A resulted in an increase of ati, ak and also no change in aka.4. GABA did not change the free intracellular Ca2+ concentration, as measured with a Ca2+-sensitive micro-electrode, whereas such an effect was seen during the action of carbachol. pH-sensitive electrodes, on the other hand, revealed a small GABA-induced extracellular acidification.5. The inward pumping of Cl-following the normal, depolarizing action of GABA required the presence of extracellular K+ as well as Na+, whereas C02/HCO3--free solutions did not influence the uptake process. Furosemide, but not DIDS, blocked the inward pumping of Cl-.6. In conclusion, our data show that only changes in intracellular activities of K+ and Cl-are associated with the action of GABA. Furthermore, they indicate that a K+/Cl-co-transport, and not a Cl-/HCO3-counter-transport, may be involved in the homoeostatic mechanism which operates to restore the normal transmembrane Cl-distribution after the action of GABA.

Kinetic Properties of Cl−Uptake Mediated by Na+-Dependent K+-2Cl−Cotransport in Immature Rat Neocortical Neurons

“…Similar values were estimated with noninvasive microfluorimetric methods (Shimizu- Ikeda et al, 2003;Zhang et al, 2006 (Rohrbough and Spitzer, 1996;Payne et al, 2003). One possible mechanism for active Cl Ϫ accumulation in neurons is Na ϩ -and K ϩ -dependent Cl Ϫ uptake (Ballanyi and Grafe, 1985;Alvarez-Leefmans et al, 1988). Such uptake can be mediated by the Na ϩ -K ϩ -2Cl Ϫ -cotransporter, a member of the cation-chloride-cotransporter family that uses the Na ϩ gradient for active Cl Ϫ accumulation and can be inhibited by loop diuretics like bumetanide (Delpire, 2000;Russell, 2000).…”

Influence of GABA‐gated bicarbonate conductance on potential, current and intracellular chloride in crayfish muscle fibres.

“…One approach is to measure the intracellular chloride activity directly by means of Cl--selective microelectrodes. Measurements of this kind have, indeed, shown that Cl-ions are actively accumulated in rat sympathetic neurones (Ballanyi & Grafe, 1985) and in amphibian dorsal root ganglion cells (AlvarezLeefmans, Gamiiio, Giraldez & Nogueron, 1988), which is compatible with the depolarizing action of GABA observed in these cells. However, an accurate measurement of the steady-state level of postsynaptic a', by means of Cl--selective electrodes is hampered by various technical problems including interference by GABA-GATED BICARBONATE CONDUCTANCE intracellular anions other than Cl-and differences in the value of the membrane potential as sensed by the ion-selective microelectrode and its reference electrode (cf.…”

“…A more promising approach is to examine whether the direction of the electrogenic Cl-flux mediated by postsynaptic anion channels is compatible with the effects of the transmitter on membrane potential (see Fig. 4, and Neild & Thomas, 1974;Ballanyi & Grafe, 1985). Nevertheless, we feel that with present electrode techniques, the most reliable way to obtain a direct estimate of E01 is to measure the reversal potential (EJ,) of instantaneous, channel-mediated Cl-fluxes (cf.…”

Action of purine and pyrimidine nucleotides on the rat superior cervical ganglion

“…It is possible that the M-current is involved in the depolarizing component of responses to ATP and ,P-MeATP but it seems unlikely that it is involved in the effect of adenosine and 1,y-MeATP in augmenting GABA-induced depolarizations. The effect of GABA on the rat SCG involves an increase in efflux of K+ and chloride ions (Ballanyi & Grafe, 1985). Therefore the ability of adenosine and P,y-MeATP to increase depolarization caused by GABA in the SCG may involve augmentation of the increased chloride efflux as reported by Ferrero & Frischknecht (1983) on guinea-pig taenia coli, or may be due to a change in the GABA-receptor/ion channel complex as described for bullfrog sensory ganglia by Morita et al (1984).…”