Tactile sensory input regulates basal and apomorphine‐induced immediate‐early gene expression in rat barrel cortex

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Abstract
Clipping of mystacial vibrissae on one side of the rat's snout result in sensorimotor asymmetries in normal behavior and in behavior induced by the dopamine receptor agonist, apomorphine. Immediate-carly gene expression, a marker for short-term changes in neuron function, was used to examine wheter this sensory deprivation leads to functional changes in the somatosensory barrel cortex under experimental conditions which reveal behavioral asymmetries. The expression of c-fos and zif 268 immediate-early genes was assessed with in situ hybridization histochemistry. Four hours after unilateral clipping of the mystacial vibrissae, the level of zif 268 mRNA was reduced in the corresponding part of the contralateral barrel field. Injection of apoorphine (5 mg/kg) resulted in increased expression of both c-fos and zif 268 immediate-early genes in cortex and striatum. This apomorphine-induced increase was blocked in the sensory-deprived somatosensory corted. Laminar analysis of gene regulation shwoed that vibrissae removal affected immediate-early expression in all layers of the barrel cortex. These results demonstrate that: (1) basal zif 268 gene expression in neurons of the somatosensory cortex is dependent on sensory input, (2) cortical immediate-early gene expression is increased after dopamine receptor activation, and (3) in the barrel cortex, this increase is also dependent on sensory input. We suggest that the observed reduction in gene expression after vibrissae removal reflects decreased activation of neurons in the barrel column by removal of sensory input.