VASCULAR-RESPONSES TO NEUROPEPTIDE-Y IN THE RAT - EFFECT OF AGE

Neuropeptide Y (NPY) is co-released with norepinephrine (NE) from symp athetic neurons, which innervate blood vessels, and acts to po tentiat e NE-induced smooth muscle contraction. This study sought to determine if vascular levels of NPY-like immunoreactivity or the contractile ef fects oi NPY are altered by age in segments of isolated blood vessels from Fischer 344 and Brown Norway-F344-F-1 rats. Tissue extracts of fe moral and tail arteries of Fischer 344 rats, aged 6, 12, 20, and 24 mo nths, were analyzed for NPY content by radioimmunoassay. Neither blood vessel shouted a significant age-related difference in NPY content. C ontractile responses of the tail artery to adrenergic transmural nerve stimulation (TNS) were compared in the same age groups. No significan t age-related differences in contractile responses to TNS were observe d in either rat strain. NPY at concentrations of 1 and 10 nM, both pot entiated and prolonged the contractile response to TNS; 6-month-old F- 344 rats were significantly less responsive to the effects of NPY. How ever; advancing age from 12 to 24 months did not alter the responses t o NPY in either mt strain. We conclude that an age-dependent increase in the contractile responses to NPY occurs from age 6 to 12 months, an d this responsiveness to NPY is maintained through senescence.