|| Checking for direct PDF access through Ovid
The concentrations of neuropeptide Y immunoreactivity were measured in microdissectedregions enriched in noradrenergic (A1, A2, A6) and adrenergic (C1, C2, C3) nuclei of thebrainstem, and in the nucleus of the spinal tract of the trigeminal nerve (Sp5C) of spontane-ously 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 neuropeptideY immunoreactivity levels related to increases in blood pressure with ageing in each ratstrain. The concentration of neuropeptide Y immunoreactivity in the A1 nucleus progres-sively fell with increasing age in both SHR and WKY. In contrast, the levels of neuropep-tide Y immunoreactivity in the C1 region fell at 18 weeks of age but did not fall furtherby 31 weeks. No significant age-related changes occurred in the concentrations of neuro-peptide Y immunoreactivity in the A2, C2, A6 and Sp5C nucleus. The levels of neuropep-tide Y immunoreactivity in the C3 region were below assay sensitivity. The neurochemicalchanges that occur in the A1 nucleus are consistent with the increase in blood pressureobserved with ageing in both rat strains. However, this observation alone does not accountfor the elevated blood pressure measured in the SHR strain.