Adenosine is involved in the arteriolar vasodilatory responses to a single skeletal muscle contraction

To investigate the role of Adenosine (Ado) in response to a single contraction we stimulated 4–5 skeletal muscle fibres in a hamster cremaster preparation and measured the diameter of arterioles at the site of overlap with the stimulated muscle fibres before and after a single contraction (250ms train duration) at 4, 20 and 60Hz. Muscle fibres were stimulated prior to and following 30min incubation with Ado receptor antagonists 1,3‐dipropyl‐8‐sulphophenylxanthine (DPSPX, 10 −5 M) or xanthine amine congener (XAC,10 −6 M), or ecto‐5′‐nucleotidase inhibitor adenosine 5′‐[α,β‐methylene]diphosphate (AMPCP,10 −5 M). A dilation within 10s was observed at 4, 20 and 60Hz (1.0±0.2; 1.5±0.2; 2.0±0.2μm respectively) which was significantly attenuated by DPSPX (4Hz −0.1±0.2; 20Hz −0.2±0.3; 60Hz 0.04±0.2μm), XAC (4Hz 0.5±0.2; 20Hz 1.0±0.2; 60Hz 0.3±0.2μm), and AMPCP (4Hz 0.03±0.1; 20Hz −0.3±0.3; 60Hz −0.3±0.2μm). A secondary dilation at 20s at 20Hz (1.4±0.3μm) and 60Hz (1.1±0.1μm) was significantly attenuated by DPSPX (20Hz −0.1±0.1; 60Hz −0.1±0.3μm), XAC (20Hz 0.3±0.2; 60Hz 0.5±0.2) and AMPCP (20Hz 0.2±0.2; 60Hz 0.02±0.1μm). These findings implicate Ado in the vasodilations in response to a single muscle contraction. NSERC