CALCITONIN-GENE-RELATED PEPTIDE LEVEL IN THE RAT DENTATE GYRUS INCREASES AFTER DAMAGE

CALCITONIN gene related peptide-like immunoreactivity (CGRP-LI) was ex amined in rat dentate gyrus (DG) following damage to granule cells by adrenalectomy or intrahippocampal colchicine injections. In normal DG, CGRP-LI was present in a diffuse Land within the inner third of the m olecular layer (ITML) and in hilar cells. Following the experimental p rocedures, levels of CGRP-LI increased bilaterally in the ITML and in hilar interneurons resembling messy cells. Ultrastructural analysis of the ITML revealed that CGRP-LI is associated with large, dense-core v esicles within axon terminals which form asymmetrical synapses with de ndritic spines, and within dendritic spines. The increase in CGRP-LI l evel following granule cell damage suggests a protective role for CGRP in the response to hippocampal injury.