Key result
In aged beagles, adrenergic receptor-mediated vasoconstriction was not elevated at rest, but nonadrenergic sympathetic vasoconstriction was altered, with reduced NPY-Y1 and increased P2x receptor-mediated restraint of skeletal muscle blood flow.
Why the study?
Does aging alter tonic adrenergic and nonadrenergic receptor-mediated sympathetic vasoconstriction in the skeletal muscle vasculature of canines at rest and during exercise?
Does aging alter tonic adrenergic and nonadrenergic receptor-mediated sympathetic vasoconstriction in the skeletal muscle vasculature of canines at rest and during exercise?
Absolute Event Rate: 91% vs 179%
p-value: p=<0.05
This study demonstrates that while aging alters nonadrenergic sympathetic vasoconstriction at rest, it does not increase adrenergic or nonadrenergic vasoconstriction during exercise in canines.
Aging alters nonadrenergic but not adrenergic vasoconstriction in beagles; hypothesis-generating for human skeletal muscle blood flow regulation.
We tested the hypothesis that tonic adrenergic and nonadrenergic receptor-mediated sympathetic vasoconstriction would increase at rest and during exercise with advancing age. Young (n = 6; 22 ± 1 mo; means ± SE) and old (n = 6; 118 ± 9 mo) beagles were studied. Selective antagonists for alpha-1, alpha-2, neuropeptide Y (NPY), and purinergic (P(2x)) receptors were infused at rest and during treadmill running at 2.5 mph and 4 mph with 2.5% grade. Prazosin produced similar increases in vascular conductance in young and old beagles at rest (Young: 158 ± 34%; Old: 98 ± 19%) and during exercise at 2.5 mph (Young: 80 ± 10%; Old: 58 ± 12%) and 4 mph and 2.5% grade (Young: 57 ± 5%; Old: 26 ± 4%). Rauwolscine caused similar (P > 0.05) increases in vascular conductance in old compared with young dogs at rest (Young: 119 ± 25%; Old: 64 ± 22%) and at 2.5 mph (Young: 86 ± 13%; Old: 60 ± 7%) and 4 mph with 2.5% grade (Young: 61 ± 5%; Old: 43 ± 7%). N2-(diphenylacetyl)-N-[4-hydroxyphenyl)methyl]-d-arginine amide (BIBP) caused a smaller increase (P < 0.05) in vascular conductance in old compared with young dogs at rest (Young: 179 ± 44%; Old: 91 ± 22%), whereas similar increases (P > 0.05) of experimental limb vascular conductance in young and old dogs occurred following BIBP during exercise at 2.5 mph (Young: 56 ± 16%; Old: 50 ± 12%) and 4 mph and 2.5% grade (Young: 45 ± 10%; Old: 25 ± 7%). Pyridoxal-phosphate-6-azophenyl-2'-4'-disulfonic acid infusion produced a larger increase in vascular conductance in old compared with young beagles at rest (Young: 88 ± 14%; Old: 191 ± 58%), whereas similar increases were observed at 2.5 mph (Young: 47 ± 18%; Old: 31 ± 11%) and 4 mph with 2.5% grade (Young: 26 ± 13%; Old: -18 ± 8%). At rest, NPY receptor-mediated restraint of skeletal muscle blood flow was reduced with advancing age, whereas P(2x) receptor-mediated restraint of skeletal muscle blood flow was increased. During exercise, the magnitude of adrenergic and nonadrenergic sympathetic vasoconstriction was not different between young and old dogs. Overall, these data demonstrate that adrenergic receptor-mediated vasoconstriction was not elevated at rest, but nonadrenergic sympathetic vasoconstriction was altered under basal conditions in aged beagles.
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DeLorey et al. (2010) studied Aging (n=12). Aging vs. Young beagles was evaluated on Increase in vascular conductance following NPY-Y1 receptor blockade (BIBP) at rest (p=<0.05). In aged beagles, adrenergic receptor-mediated vasoconstriction was not elevated at rest, but nonadrenergic sympathetic vasoconstriction was altered, with reduced NPY-Y1 and increased P2x receptor-mediated restraint of skeletal muscle blood flow.
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