Question

GABA_A receptors provide most of the fast inhibitory synaptic transmission in the adult brain. These receptors are GABA-gated channels that are typically viewed as being permeable to chloride anions. However, GABA_A receptors are permeable to chloride as well as bicarbonate (HCO₃^-) anions. If you measured GABA_A currents in an experiment, describe how you would go about figuring out the relative permeability of the GABA_A receptor to chloride and bicarbonate

Answer 1

Answer:- Ca2+ imaging and patch recording were used to analyse the mechanism of GABA and glycine induced depolarisation . The rises in Ca2+ were potentiated by >300% immediately after removal of Cl- from the superfuscate but recovered of values of 50-200% of control during repeated agonist administration of Cl- free saline. Removal of HCO3- decreased both the peak and duration of the agonist induced [Ca2+] response. HCO3- decreased both the peak and duration of the agonist evoked membrane depolarisation and Ca2+ response. HCO3- efflux has a major contribution to depolarisation mediated by GABA receptor coupled anion channels in prenatal neurons. HCO3- dependent depolrising component, which is likely to produce an intracellular acidosis, might play an important role during easy postnatal period when Cl- dependent component gradually shifts to hyperpolarisation.