Effects of Whisker-trimming on Gabaa Receptors in S1 Cortex

A number of studies have shown that sensory deprivation is associated with selective decreases in GABA, GAD, and GABA receptors, in deprived areas of visual and somatosensory cortex. Those studies focused on layer 4, a recipient of direct thalamocortical sensory input. However, supragranular layers 2/3 have been recently identified as a major locus of functional plasticity in sensory deprivation and long-term potentiation. To examine whether GABA A receptors in layers 2/3 are affected by sensory deprivation, rats had mystacial vibrissae in middle row C or rows ABDE trimmed for 6 weeks beginning in early adulthood. Layers 2/3 above the deprived and adjacent whisker barrels were located in tangential sections, using patterns of radial blood vessels as fiducial marks. In deprived whisker barrel columns, [ 3 H]muscimol binding to GABA A receptors decreased by 12.8% ± 1.2 (P<0.001) in layers 2/3 and 11.4% ± 1.2 (P<0.001) in layer 4. Altered levels of GABA A α1 subunit (Fritschy et al., 1994) were indicated by reduced optical density of immunostaining, both in deprived layers 2/3 (6.4% ± 0.7;