The concentration of neuropeptide Y immunoreactivity falls with age selectively in microdissected regions of the ventrolateral medulla of spontaneously hypertensive and normotensive Wistar-Kyoto rats.

The concentrations of neuropeptide Y immunoreactivity were measured in microdissected regions enriched in noradrenergic (A1, A2, A6) and adrenergic (C1, C2, C3) nuclei of the brainstem, and in the nucleus of the spinal tract of the trigeminal nerve (Sp5C) of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats at 8, 18 and 31 weeks of age. The aim of this study was to compare the manner in which changes in neuropeptide Y immunoreactivity levels related to increases in blood pressure with ageing in each rat strain. The concentration of neuropeptide Y immunoreactivity in the A1 nucleus progressively fell with increasing age in both SHR and WKY. In contrast, the levels of neuropeptide Y immunoreactivity in the C1 region fell at 18 weeks of age but did not fall further by 31 weeks. No significant age-related changes occurred in the concentrations of neuropeptide Y immunoreactivity in the A2, C2, A6 and Sp5C nucleus. The levels of neuropeptide Y immunoreactivity in the C3 region were below assay sensitivity. The neurochemical changes that occur in the A1 nucleus are consistent with the increase in blood pressure observed with ageing in both rat strains. However, this observation alone does not account for the elevated blood pressure measured in the SHR strain.