An acute bout of dynamic exercise is often followed by sustained hypotension. We previously showed that caffeine raises blood pressure (BP) at rest without increasing sympathetic nerve activity, supporting a tonic vasodilatory effect of adenosine. The potential contribution of adenosine to post-exercise hypotension (PEH) is unknown. We therefore studied heart rate (HR), BP and plasma catecholamine responses in 12 healthy middle-aged men (mean age = 52 ± 4 yrs), at rest, during and 10 minutes after graded cycle exercise to peak effort, following a randomized double-blind administration of intravenous caffeine (4mg/kg) or vehicle. Both studies followed 72 hours of caffeine abstinence. BP significantly increased after caffeine vs vehicle during supine rest (P<0.05; plasma caffeine=54.2 mmol/L), but there was no difference once seated upright. Peak exercise HR and plasma epinephrine were significantly increased on the caffeine day vs vehicle (P<0.05), but peak BP, plasma norepinephrine, and oxygen uptake were unaffected. Caffeine resulted in a higher post-exercise HR (97.8+ 4.93 bpm) vs vehicle (89.7± 5.75 bpm; P<0.05) and prevented PEH (mean BP post-exercise=90.2 ± 1.81 mmHg vs 95.0 ± 2.1 pre-exercise) which occurred with vehicle (85.3 ± 2.44 vs 93.3 ± 2.49; P<0.05). These data suggest a role for adenosine in PEH in healthy subjects and underscore the need for controlled caffeine abstinence in PEH studies.

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