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Sex and aging interact to modulate the rapid onset of arteriolar dilation in mouse skeletal muscle

Aging is associated with a reduction in blood flow to skeletal muscle and diminished exercise capacity. However, little is understood of how aging affects arteriolar dynamics in working skeletal muscle. We tested the hypothesis that aging impairs the rapid onset of vasodilation (ROV) in mouse gluteus maximus muscle. Responses of second‐order arterioles [diameter: rest, 17 ± 1 μm; max (SNP), 29 ± 1 μm] to single tetanic contractions (100 Hz) were assessed in anesthetized C57Bl/6 mice using intravital microscopy in Young (3 mo) males (YM; n=7) and females (YF; n=5) and in Old (~20 mo) males (OM; n=7) and females (OF; n=6). With increasing stimulus duration (100–1000 ms), the magnitude of dilation increased (from 1 to 7 μm) in YM, YF, and OF (P<0.05) yet ROV was blunted consistently by >50% in OM (P<0.05). In contrast, 30‐s rhythmic contractions at 2, 4, and 8 Hz resulted in steady‐state dilations that increased with frequency (from 2 to 8 μm; P<0.05) and were not different between groups. Remarkably, the decrement in ROV in OM was reversed (P<0.05) with α‐adrenoreceptor blockade (1 μM phentolamine).