|
VISUAL ACTIVATION OF IMMEDIATE EARLY GENES IN REWIRED
AUDITORY CORTEX AFTER EARLY INDUCTION OF RETINAL PROJECTIONS INTO THE
AUDITORY THALAMUS
|
|
|
|
| Neonatal ablation of the inferior colliculus, the predominant
auditory input to the medial geniculate nucleus (MGN), causes retinal axons
to innervate the MGN. This manipulation alters the flow of stimulus-driven
activity to, and within, the developing cortex. To examine the interplay
of genes, input activity, and plasticity in the cortex, we have asked: 1)
Does visual stimulation activate immediate early gene transcription in rewired
A1? 2) Is the pattern of visual activity-dependent stimulus transduction
similar in rewired A1 versus normal V1? Mice were rewired on the day of birth and reared to adulthood. Normal mice and rewired mice were dark-housed for 2 days, and exposed to 20 min or 2 h of strong visual stimulation without auditory stimulation. The brains were processed for immunohistochemistry of immediate early gene products, including c-fos, egr-1, p-Elk-1, p-c-Jun and p-CREB. Unilaterally rewired mice showed strong visual activation of c-fos that was stronger in rewired A1 than in normal A1. Bilaterally rewired mice showed strong, but asymmetric, activation of c-fos in right and left A1's. The laminar pattern of c-fos activation in rewired A1 was similar to that in primary visual cortex (V1). Egr-1 expression was strong in V1 and rewired A1, showing a complex multilaminar pattern. p-CREB expression was uniformly strong and did not predict c-fos or egr-1 expression. p-c-Jun and p-Elk-1 patterns were weak. These data suggest that visual activity can regulate the expression of certain immediate early genes in rewired A1, and in a manner similar to that in V1. Supported by: NIH grant NS39022. |