Re-establishment of electrophysiologically functional entorhinal cortical input to the dentate gyrus deafferented by ipsilateral entorhinal lesions: innervation by the contralateral entorhinal cortex.

Abstract

We have unilaterally ablated the entorhinal cortex of the developing rat, thereby removing the major synaptic input to the ipsilateral dentate gyrus. We have then examined the efferent projections of the remaining contralateral entorhinal cortex to determine if these might reoccupy the synaptic territory vacated by the ipsilateral entorhinal fibers. By placing lesions in the remaining contralateral entorhinal cortex, and tracing the resulting degeneration products, we show that the contralateral entorhinal projection is reorganized, establishing an anomalous terminal projection to the dentate gyrus deafferented by the initial lesion. The result is a contralateral entorhinal innervation of the dentate gyrus which normally receives only ipsilateral entorhinal afferents.