Age-related changes in tissue contents of immunoreactive calcitonin gene-related peptide

Age-related changes in calcitonin gene-related peptide (CGRP) content were found in a number of rat tissues, and most can be explained by the physiological and pathological changes associated with advancing age. In some specific areas of the brain, and some cardiovascular tissues such as atria and arteries, the CGRP content declined with age (p < 0.01), while the contents were increased in the thyroid gland, plasma and in veins (p < 0.01). In the substantia nigra and striatum, the immunoreactive-CGRP (i-CGRP) levels found in older rats were about 50% of those found in adolescent rats (p < 0.01). The i-CGRP levels found in the penis, bladder, kidney, testis and adrenal gland gradually increased up to maturity, and then rapidly declined in the aging rats. However, in the lungs and sensory ganglia (dorsal root and trigeminal), the highest content of i-CGRP was found in immature 3-week-old rats, and then declined with age. Changes of i-CGRP observed with age may support multiple physiological roles for CGRP at various stages of development. The changes described here, particularly in the lungs, substantia nigra, striatum and the cardiovascular system, should help in further understanding the physiological and pathophysiological role of CGRP in health and in age-related disorders.