Neuron type reconfiguration of GABA--ergic tonic inhibition in mouse barrel cortex induced by sensory learning
Pairing tactile stimulation of a row of whiskers with a tail shock results in expansion of the cortical representation of stimulated vibrissae accompanied by increase of the GABAergic markers. Using the same paradigm, we examined exstrasynaptic GABAA receptors-mediated tonic inhibition. Whole-cell patch-clamp recordings were performed in layer IV neurons and tonic current was assessed by application of the GABAA receptors blocker-picrotoxin (PTX) or by 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin3-ol (THIP, a superagonist at delta-subunit containing GABAA receptors) in ex vivo slices of the barrel cortex in adult mice. PTX and THIP produced greater shifts in baseline holding current in excitatory cells within the cortical representation of “trained” vibrissae, visible 24 hours after the end of training. Recordings from layer IV fast spiking neurons showed that the training induced smaller baseline shifts after the application of both substances. Regular spiking non-piramidal neurons had similar shifts in baseline holding current in both control and trained mice. These data indicate that associative learning paradigm results in a neuron type reconfi guration in tonic inhibition of layer IV neurons situated within the barrel representing stimulated vibrissae. This reconfi guration can be caused by changes in the level of deltasubunit containing GABAA receptors. Supported by the Ministry of Science and Higher Education grants PBZ/MNiSW/07/2006/02 and N401 028 32/0664.