NGFI-C expression is affected by physiological stimulation and seizures in the somatosensory cortex

NGFI-C is an early response gene which encodes a Cys2/His2 zinc finger protein. NGFI-C has previously been demonstrated to be inducible in PC12 cells after NGF stimulation. This study sought to localize this gene in somatosensory cortex, and investigate its possible induction by physiological and seizure stimuli. To determine if NGFI-C message levels are affected by stimulation, RT-PCR was performed on mRNA extracts from somatosensory cortex. NGFI-C mRNA levels were increased to levels four-fold over baseline after a seizure. In a paradigm used as a model of experience-dependent plasticity, vibrissae stimulation also increased the level of NGFI-C expression in the contralateral barrel cortex to 180% of control levels. In situ analysis using digoxigenin-labelled cRNA probes demonstrated NGFI-C containing neurons throughout layers 2 through 6 in somatosensory cortex. A higher cell density was seen after stimulation. Qualitatively, staining was more intense in post-seizure and post-stimulus cortex than in control cortex. Analysis of related zinc finger expression in serial sections revealed that NGFI-C is expressed in a distinct but overlapping cell populations relative to NGFI-A, Krox 20, and Egr-3. These studies demonstrate the inducible nature of NGFI-C message in response to a physiological vibrissae stimulus, as well as to seizures. However, the levels and pattern of expression differ between these two stimuli.