Are decreases in insular regional cerebral blood flow sustained during postexercise hypotension?

Regional cerebral blood flow (rCBF) in the insular cortex (IC), a well-recognized site for central blood pressure (BP) modulation, is decreased at minute 10 during postexercise hypotension (PEH). PURPOSE: To determine whether exercise-induced decreases in IC rCBF are associated with BP changes throughout PEH. METHODS: Ten subjects were studied on three different days using a counterbalanced design with a randomized order for conditions; all were tested during a resting baseline and then at two of three time points postexercise: 10, 30, and 60 min. Data were collected for HR, mean BP, and rCBF using single-photon emission computed tomography as an index of brain activation. RESULTS: Using ANOVA across conditions, there were differences (P < 0.05; mean ± SD) for HR from baseline at minute 10 (+15 ± 4 bpm) and minute 30 (+6 ± 3 bpm) and for mean BP at minute 10 (-11 ± 4 mm Hg) and minute 30 (-5 ± 3 mm Hg). There were significant decreases (P < 0.05) in rCBF at both minutes 10 and 30 after exercise in the inferior thalamus and the right inferior IC regions. Although there were no decreases in BP or IC activity at minute 60, changes in right inferior posterior IC activity and BP were strongly correlated (r = 0.74; P < 0.05) postexercise. CONCLUSIONS: Findings show that exercise-induced decreases in IC and thalamic activity may be a significant neural factor contributing to at least the first 30 min of PEH.