Histaminergic and cholinergic neuron systems in the impairment of human thermoregulation during motion sickness.
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.
Nobel
Gerard
G
Department of Environmental Physiology, Royal Institute of Technology, School for Technology and Health, Berzelius v. 13, SE 171 65 Stockholm, Sweden. nobel_gerard@hotmail.com
Tribukait
Arne
A
Mekjavic
Igor B
IB
Eiken
Ola
O
D000328:Adult; D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D018680:Cholinergic Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D004111:Dimenhydrinate / Q000494:pharmacology / Q000627:therapeutic use; D006632:Histamine / Q000378:metabolism; D006634:Histamine H1 Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007036:Hypothermia, Induced; D008297:Male; D009041:Motion Sickness / Q000188:drug therapy / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism; D010101:Oxygen Consumption; D010919:Placebos; D012601:Scopolamine / Q000494:pharmacology / Q000627:therapeutic use; D055815:Young Adult
D018680:Cholinergic Antagonists; D006634:Histamine H1 Antagonists; D009479:Neuropeptides; D010919:Placebos; D006632:Histamine; D012601:Scopolamine; D004111:Dimenhydrinate