The temporal neurovascular coupling response remains intact during sinusoidal hypotensive and hypertensive challenges

Abstract

Abstract Introduction. Neurovascular coupling (NVC) describes the coupling of neuronal metabolic demand to blood supply, which has shown to be impaired with chronic hypertension, as well as with prolonged hypotension. However, it is unknown the extent the NVC response remains intact during transient hypo- and hyper-tensive challenges. Methods. Fifteen healthy participants (9 females/6 males) completed a visual NVC task (‘Where’s Waldo?’) over two testing sessions, consisting of cyclical 30 s eyes closed and opened portions. The Waldo task was completed at rest (8 min) and concurrently during squat-stand maneuvers (SSMs; 5 min) at 0.05 Hz (10 s squat/stand) and 0.10 Hz (5 s squat-stand). SSMs induce 30–50 mmHg blood pressure oscillations, resulting in cyclical hypo- and hyper-tensive swings within the cerebrovasculature, allowing for the quantification of the NVC response during transient hypo- and hyper-tension. Outcome NVC metrics included baseline, peak, relative increase in cerebral blood velocity (CBv), and area-under-the-curve (AUC30) within the posterior and middle cerebral arteries indexed via transcranial Doppler ultrasound. Within-subject, between-task comparisons were conducted using analysis of variance with effect size calculations. Results. Differences were noted between rest and SSM conditions in both vessels for peak CBv (all p < 0.045) and the relative increase in CBv (all p < 0.049) with small-to-large effect sizes. AUC30 metrics were similar between all tasks (all p > 0.090) with negligible-to-small effect sizes. Conclusions. Despite the SSMs eliciting ∼30–50 mmHg blood pressure oscillations, similar levels of activation occurred within the neurovascular unit across all conditions. This demonstrated the signaling of the NVC response remained intact during cyclical blood pressure challenges.