INIBIBB   05455
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BAHIA BLANCA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The physiological role of potassium-chloride cotransporters (KCCs) in the cerebellum
Autor/es:
SEJA PATRICIA; SPITZMAUL, GUILLERMO; THOMAS J. JENTSCH
Lugar:
Amsterdam
Reunión:
Congreso; 7th FENS Forum of European Neuroscience.; 2010
Resumen:
Cation chloride cotransporters mediate a coupled
electroneutral movement of Cl-, K+ and Na+ across plasmamembranes in many
cells. The neuron-specific KCl cotransporter KCC2 is thought to lower the intracellular
Cl- concentration below its electrochemical equilibrium potential by using the
outwards directed gradient of K+ as a driving force. This low intracellular Cl-
concentration is required for the fast inhibitory action of GABA which is
mediated by the GABAA receptor, a ligand-gated anion channel. The activation of
GABAA receptors drives the membrane potential of a cell towards EGABA, the
reversal potential of GABAergic currents. In immature neurons, GABA is
excitatory, as EGABA is above the resting membrane potential. The expression of
KCC2 correlates with the drop of EGABA below the resting membrane potential,
and thereby the switch from excitatory to inhibitory GABA signaling. The KCl
cotransporter KCC3 is expressed more broadly and involved in cell volume regulation.
Nevertheless, while KCC2 may be the key regulator of neuronal [Cl-]i, a similar
role was proposed for KCC3.
To investigate the physiological role of KCC2 and KCC3
in the murine cerebellum at cellular level, we specifically delete the KCCs in
cerebellar Purkinje cells and Granule cells by breeding floxed mice with
alpha6-Cre- and L7-Cre-mice, respectively. To investigate a possible role for
GABAergic inhibition on the cellular level we record from acute slices with the
perforated patch technique. We showed that GABAergic currents of wildtype
Purkinje cells (>P25) reverse around -95 mV. For KCC2-/- Purkinje cells this
reversion is shifted to more positive potentials, but still remains hyperpolarising.
Granule cells of wildtype mice show a strong membrane staining for KCC2. Surprisingly,
the driving force for Cl- in respect to the resting membrane potential was not
altered in granule cells lacking KCC2. It would be feasible to examine the
cerebellar circuit by stimulating parallel fibers while recording from Purkinje
cells. The feed forward inhibition in this circuitry should be altered in
knockout mice. These experiments might give answers to the question how the
cerebellar network is processing information.