Differences between cation-chloride co-transporter functions in the visual cortex of pigmented and albino
rats
G. Barmashenko, M. Schmidt & K.-P. Hoffmann
European Journal of Neuroscience 21:1189-1195, 2005
- Eur.J.Neurosci., 21,1189-1195,2005
Albinism in mammals is accompanied by specific morphological and functional alterations of the visual system. To
understand their cellular basis we studied the physiological characteristics and transmembrane currents of pyramidal
neurons in 350-microm-thick slices of visual cortex from pigmented and albino rats using whole-cell and gramicidin
perforated patch-clamp recordings. The resting membrane potential was significantly more positive and the rheobase
was significantly lower in neurons of layers II/III and V in albinos as compared with pigmented rats. No significant
differences were found in the input resistance, time constant and chronaxy. Whereas the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid receptor-mediated currents were not significantly different, the maximum gamma-aminobutyric acid (GABA)(A)
receptor (GABA(A)R)-mediated currents and miniature inhibitory postsynaptic currents showed significantly lower
amplitudes in neurons of layer V in visual cortex of albinos as compared with pigmented rats. The reversal potential
of the GABA(A)R-mediated currents (E(GABA)) was significantly shifted to more positive values in albinos. Pharmacological
experiments showed that this shift could be caused by an increased action of the inward chloride co-transporter
NKCC1 and reduced action of the outward chloride co-transporter KCC2 in albino rats. This difference seems to be
restricted to the visual cortex because in pyramidal neurons from frontal cortex E(GABA) was not significantly
different in albinos as compared with pigmented rats. These results are discussed in relation to functional alterations
in the albino visual system.
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