Qy. Liu et al., EXOGENOUS GABA PERSISTENTLY OPENS CL- CHANNELS IN CULTURED EMBRYONIC RAT THALAMIC NEURONS, The Journal of membrane biology, 145(3), 1995, pp. 279-284
We recorded whole-cell Cl- currents in cultured embryonic rat thalamic
neurons by brief applications of GABA or the structural analogue musc
imol. In 17 of 141 neurons (12%) the Cl- current persisted for a minut
e or more after the pipette was removed from the bath. Cl- current nev
er persisted after muscimol exposure even in those cells exhibiting pe
rsistent GABA-activated currents (PGC). The half decay times (T-50) of
PGCs were exponentially and asymptotically related to the duration of
GABA exposure and could be interrupted or completely aborted by low-p
ressure application of saline. PGCs were insensitive to membrane poten
tial, to Tiagabine, a nipecotic acid analogue known to block GABA upta
ke, and persisted in Ca-o(2+)-free medium. Fluctuation analysis reveal
ed that PGCs exhibited inferred Cl- channel properties whose kinetic c
omponents and estimated average elementary conductance showed no signi
ficant difference from those estimated during GABA exposure. The relat
ive contribution of low frequency components was consistently reduced
and that of high frequency components modestly increased during PGC co
mpared to those recorded during GABA exposure. Taken together, the res
ults suggest the existence of a superficial compartment in these embry
onic neurons that can momentarily accumulate and release exogenous GAB
A.