Motion sickness (MS) exaggerates body cooling during cold-water immersion. The aim of the present study was to investigate whether such MS-induced predisposition to
hypothermia is influenced by two anti-MS drugs: the
histamine-receptor blocker
dimenhydrinate (
DMH) and the
muscarine-receptor blocker
scopolamine (Scop). Nine healthy male subjects were immersed in 15 degrees C water for a maximum of 90min in five conditions: (1) control (CN): no medication, no MS provocation; (2) MS-control (MS-CN): no medication, MS provocation; (3) MS-placebo (MS-P): placebo
DMH and placebo Scop, MS provocation; (4) MS-
DMH:
DMH and placebo Scop, MS provocation; (5) MS-Scop: Scop and placebo
DMH, MS provocation. MS was induced by use of a rotating chair. Throughout the experiments rectal temperature (T(re)), the difference in temperature between the non-immersed right forearm and third finger (T(ff)) as an index of peripheral vasoconstriction, and
oxygen uptake (VO(2)) as a measure of shivering thermogenesis, were recorded.
DMH and Scop were similarly efficacious in ameliorating
nausea. The fall in T(re) was greater in the MS-CN and MS-P conditions than in the CN condition.
DMH, but not Scop, prevented the MS-induced increase in body-core cooling. MS attenuated the cold-induced vasoconstriction, an effect which was fully prevented by
DMH but only partially by Scop. MS provocation did not affect VO(2) in any condition. The results suggest that the MS-induced predisposition to
hypothermia is predominantly mediated by histaminergic mechanisms and that
DMH might be useful in conjunction with maritime accidents or other scenarios where exposure to cold and MS are imminent features.