DIFFERENTIAL EXPRESSION OF AN INWARDLY RECTIFYING CHLORIDE CONDUCTANCE IN RAT-BRAIN NEURONS - A POTENTIAL MECHANISM FOR CELL-SPECIFIC MODULATION OF POSTSYNAPTIC INHIBITION

A voltage-sensitive inwardly rectifying chloride (Cl-) conductance (G( Cl(V))) is present in hippocampal pyramidal but not dentate gyrus neur ons and has a significant role in modulation of neuronal inhibition by GABA. G(Cl(V)) has the same activation properties as the cloned and e xpressed Cl- channel ClC-2. In brain, ClC-2 was detected selectively i n neurons, and in hippocampus was detected in the same populations of neurons that demonstrate G(Cl(V)). ClC-2 mRNA expression varied widely in different neuronal populations in brain but was greatest in pyrami dal and other large neurons and least in interneurons. The observed di fferential expression of ClC-2 provides a potential molecular basis fo r the paradoxical excitation produced by GABA(A) receptor activation i n selected neuronal populations.