Infusion of D-cycloserine into temporal-hippocampal areas and restoration of mnemonic function in rats with disrupted glutamatergic temporal systems.

Partial transections of the fiber connections between the temporal cortex and the lateral entorhinal cortex at a site of the white matter corresponding to the perirhinal cortex result in impaired visual memory accompanied by reduced concentrations of glutamate in both the temporal cortex and lateral entorhinal cortex. Intraperitoneal administration of the glycinergic receptor agonist D-cycloserine produces complete restoration of memory function, as measured by a brightness discrimination task in rats with temporal cortex/lateral entorhinal cortex transections. The purpose of the present study was to identify in which brain structures the compensatory activity might take place. The results show that infusion of cycloserine into either the temporal cortex or lateral entorhinal cortex fully ameliorated the impairment of temporal cortex/lateral entorhinal cortex lesions, whereas infusion into the hippocampal region caused only a mild improvement of the retention performance. Infusion of cycloserine into the frontal cortex or saline into the temporal cortex or lateral entorhinal cortex had no ameliorating effects on the memory dysfunction of rats bearing temporal cortex/lateral entorhinal cortex transections. It is concluded that the temporal cortex, lateral entorhinal cortex and perirhinal cortex are highly critical in forming visual memory.