Key Points
- To determine whether nitric oxide directly contributes to exercise hyperaemia or interacts with adenosine generation and receptor-mediated vasodilation during muscle contractions.
- Anaesthetized rats were monitored for femoral vascular conductance and hindlimb oxygen consumption at rest and during 4 Hz isometric twitch contractions across three experimental groups.
- Assessed adenosine A(2A)-receptor blockade with ZM241385 after nitric oxide synthase inhibition via L-NAME, and after restoring baseline conductance with an NO donor (SNAP) or cell-permeant cGMP (8-bromo-cGMP).
- Exercise hyperaemia decreased significantly by 32% after L-NAME treatment and was further attenuated by ZM241385 to 60% below baseline control.
- Following restoration of baseline vascular conductance with SNAP or 8-bromo-cGMP, L-NAME had no effect on hyperaemia, but ZM241385 still caused a significant 25% reduction.
Structured PICO
PPopulationAnaesthetized rats (three groups)
IInterventionA(2A)-receptor inhibition with ZM241385 after NO synthase inhibition with l-NAME, and with femoral vascular conductance restored by NO donor (SNAP) or cell-permeant cGMP
CComparatorControl conditions (before inhibition)
OOutcomeFemoral vascular conductance (FVC) and hindlimb O(2) consumption at rest and during isometric twitch contractions (4 Hz)surrogate
Nitric oxide is not required for adenosine release during muscle contraction, and adenosine-mediated vasodilation during exercise hyperaemia occurs independently of new NO synthesis.