Vascular responses to neuropeptide Y in the rat: effect of age

Neuropeptide Y (NPY) is co-released with norepinephrine (NE) from sympathetic neurons, which innervate blood vessels, and acts to potentiate NE-induced smooth muscle contraction. This study sought to determine if vascular levels of NPY-like immunoreactivity or the contractile effects of NPY are altered by age in segments of isolated blood vessels from Fischer 344 and Brown Norway-F344-F-1 rats. Tissue extracts of femoral and tail arteries of Fischer 344 rats, aged 6, 12, 20, and 24 months, were analyzed for NPY content by radioimmunoassay. Neither blood vessel showed a significant age-related difference in NPY content. Contractile responses of the tail artery to adrenergic transmural nerve stimulation (TNS) were compared in the same age groups. No significant age-related differences in contractile responses to TNS were observed in either rat strain. NPY, at concentrations of 1 and 10 nM, both potentiated and prolonged the contractile response to TNS; 6-month-old F-344 rats were significantly less responsive to the effects of NPY. However, advancing age from 12 to 24 months did not alter the responses to NPY in either rat strain. We conclude that an age-dependent increase in the contractile responses to NPY occurs from age 6 to 12 months, and this responsiveness to NPY is maintained through senescence.