Background and objective: The effects of clonidine and dopamine, both alone and together, on gastric tone were studied using an electronic barostat. This enabled volume changes to be measured in an intragastric bag with constant preset pressure.

Methods: Nine healthy male volunteers were each studied on two occasions in a randomized order. During each study period, a continuous infusion of dopamine was given, starting with a dose of 2.5 μg kg−1 min−1 and then increasing at 15-min intervals to 5.0 and 7.5 μg kg−1min 2 1. Clonidine 150 μg intravenously was given on one occasion during the infusion of dopamine (7.5 μg kg−1min−1) and on the other occasion 15 min before the dopamine infusion started.

Results: During dopamine infusion, the intragastric bag volume increased (gastric tone therefore decreasing) in a dose-related manner (total increase 290 6 114 mL). Clonidine given either during or before dopamine infusion did not influence the bag volume. When the dopamine infusion started 15 min after clonidine, the bag volume did not change until the infusion of dopamine reached 7.5 μg kg−1min−1(total increase 205 6 156 mL).

Conclusions: Dopamine reduced gastric tone in a dose-related manner, and clonidine did not influence gastric tone per se. If clonidine is given before dopamine, the effects of dopamine are reduced.