Effect of cyclooxygenase inhibition on the inspiratory muscle metaboreflex-induced cardiovascular consequences in men

Inspiratory muscle metaboreflex activation increases mean arterial pressure (MAP) and limb vascular resistance (LVR) and decreases limb blood flow (Q^̇_L). Cyclooxygenase (COX) inhibition has been found to attenuate limb skeletal muscle metaboreflex-induced increases in muscle sympathetic nerve activity. We hypothesized that compared with placebo (PLA), COX inhibition would attenuate inspiratory muscle metaboreflex-induced 1) increases in MAP and LVR and 2) decreases in Q^̇_L. Seven men (22 ± 1 yr) were recruited and orally consumed ibuprofen (IB; 10 mg/kg) or PLA 90 min before performing the cold pressor test (CPT) for 2 min and inspiratory resistive breathing task (IRBT) for 14.9 ± 2.0 min at 65% of maximal inspiratory pressure. Breathing frequency was 20 breaths/min with a 50% duty cycle during the IRBTs. MAP was measured via automated oscillometry, Q^̇_L was determined via Doppler ultrasound, and LVR was calculated as MAP divided by Q^̇_L. Electromyography was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to greater increases (P = 0.02) in 6-keto-prostaglandin-F₁ with PLA compared with IB. IB, compared with PLA, led to greater (P < 0.01) increases in MAP (IB: 17 ± 7 mmHg vs. PLA: 8 ± 5 mmHg) and LVR (IB: 69 ± 28% vs. PLA: 52 ± 22%) at the final minute of the 65% IRBT. The decrease in Q^̇_L was not different (P = 0.72) between IB (-28 ± 11%) and PLA (-27 ± 9%) at the final minute. The increase in MAP during the CPT was not different (P = 0.87) between IB (25 ± 11 mmHg) and PLA (24 ± 6 mmHg). Contrary to our hypotheses, COX inhibition led to greater inspiratory muscle metaboreflex-induced increases in MAP and LVR. NEW & NOTEWORTHY Cyclooxygenase (COX) products play a role in activating the muscle metaboreflex. It is not known whether COX products contribute to the inspiratory muscle metaboreflex. Herein, we demonstrate that COX inhibition led to greater increases in blood pressure and limb vascular resistance compared with placebo during inspiratory muscle metaboreflex activation.