Effects of a mental task on splanchnic blood flow in fasting and postprandial conditions

We tested the hypothesis that a mental task attenuates the meal-induced vasodilation in the splanchnic vasculature. Ten subjects performed a 5-min colour-word conflict test (CWT) under fasting and postprandial conditions. Subjects in the postprandial condition had ingested solid food with an energy content of 300 kcal (1,255 kJ) before either performing the CWT (mental task trial) or resting (resting control trial). The mean blood velocities (MBV) in the coeliac artery (CA) and superior mesenteric artery (SMA), and the mean arterial pressure (MAP) were measured. The MBV in the CA and SMA were divided by the MAP to assess the vascular conductance (VC). The MBV in the CA and SMA were significantly increased by the CWT under fasting conditions. In the postprandial condition, the MBV in the CA and SMA significantly increased immediately after the meal in both the mental task and resting control trials. The VC in the SMA, but not in the CA, was significantly decreased by the CWT under fasting conditions. In the postprandial conditions, there was no significant difference in the VC in both arteries between mental task and resting control trials. These results suggest that a mental task exerts different effects on the CA and SMA under fasting but not postprandial condition. The vasoconstrictive effect of a mental task on the SMA does not counter the vasodilatory effect of meal ingestion.