Gastric myoelectrical and autonomic cardiac reactivity to laboratory stressors.

Gianaros PJ, Quigley KS, Mordkoff JT, Stern RM.

Cardiovascular Behavioral Medicine Research Program, The University of Pittsburgh, PA, USA. pjg4 pitt.edu

We evaluated the effects of two laboratory stressors (speech preparation and isometric handgrip) on gastric myoelectrical and autonomic cardiac activity, and the extent to which autonomic responses to these stressors and somatization predict reports of motion sickness during exposure to a rotating optokinetic drum. Both stressors prompted a decrease in preejection period (PEP) and respiratory sinus arrhythmia (RSA), and an increase in a dysrhythmic pattern of gastric myoelectrical activity, termed gastric tachyarrhythmia. Stressor-induced decreases in RSA and higher somatization scores predicted increased reports of motion sickness during drum rotation. These results demonstrate that laboratory stressors concurrently affect gastric myoelectrical activity and autonomic control of the heart, and that stressor-induced decreases in RSA and higher levels of somatization predict motion sickness susceptibility.

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Motion sickness in amphibians.

Wassersug RJ, Izumi-Kurotani A, Yamashita M, Naitoh T.

Department of Biology, Shimane University, Matsue, Japan.

We explored the question of whether amphibians get motion sickness by exposing anurans (frogs) and urodeles (salamanders) to the provocative stimulus of parabolic aircraft flight. Animals were fed before flight, and the presence of vomitus in their containers after flight was used to indicate motion-induced emesis. None of the species that we studied vomited during the 8 to 10 parabolas of each flight. However, at least one specimen from each of the anuran species Rana rugosa, Rana nigromaculata, Hyla japonica, and Rhacophorus schlegelii vomited in a period of 0.5 to 42 h after flight. Some specimens of R. nigromaculata, H. japonica, and R. schlegelii were also observed retching without emesis either during or shortly after exposure to parabolic flight. We were unable to induce either emesis or retching behavior in the aquatic from Xenopus laevis. Among the urodeles studied we saw no signs of motion sickness in either adult or larval Cynops pyrrhogaster, but at least one larval Hynobius nebulosus vomited shortly after parabolic flight. The amphibian species that exhibited the most motion sickness were the same ones that showed the greatest amount of tumbling during the microgravity phases of their parabolic flights. The most distinctive difference between motion sickness in amphibians and mammals that vomit, including man, is the long delay between a provocative stimulus and emesis proper in the amphibians. The retching behavior we induced in the frogs was identical to that described previously for frogs treated with emetic drugs. H. japonica, exposed to extended periods of microgravity on the MIR Space Station, flattened their bellies against the substrate and dorsiflexed their heads in a manner reminiscent of drug-induced nausea. In light of our current observations of retching behavior in motion sick H. japonica, we suggest that the previously observed behavior of three frogs on the MIR Space Station was a manifestation of motion sickness.

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Autonomic function and plasma catecholamines following stressful sensory stimuli.

Kohl RL.

Space Biomedical Research Institute, National Aeronautics and Space Administration, Johnson Space Center, Houston, TX.

This experimentation defined a limited role for epinephrine in the autonomic nervous system function and the nausea that occurred following motion sickness testing. Individual responses to stressful sensory stimuli and nausea, as reflected by rising peripheral levels of epinephrine, were not significantly diminished upon repeated exposure and adaptation to the stressor. However, subjects who demonstrated more robust elevations of epinephrine in response to nausea displayed higher resistances to stressful motion stimuli. Modulation of peripheral catecholaminergic function with dexamethasone, or scopolamine plus amphetamine, suggested that altered autonomic nervous system function and nausea following motion sickness testing were not mediated by peripheral catecholamine receptor stimulation. Marked differences were noted in individual responses to drug and systemic responses of epinephrine and norepinephrine. It is possible that responses in epinephrine to motion sickness testing may predict resistance to stressful motion, and represent a peripheral manifestation of some as yet unknown central event of etiologic relevance.

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Correlates of military tank simulator sickness.

Lerman Y, Sadovsky G, Goldberg E, Kedem R, Peritz E, Pines A.

Israel Defence Force, Medical Corps.

A military tank driving simulator is currently widely used as a training aid for tank drivers. The purpose of this study was to investigate the relationship between possible correlates of simulator sickness and the occurrence of sickness and performance test results among simulator drivers. The average number of motion sickness-like symptoms reported after driving the simulator among subjects with a history of susceptibility to motion sickness was 3.4, significantly higher than the average of 1.6 reported among subjects who did not report previous susceptibility to motion sickness (p < 0.05). Subjects driving the simulator while screen image quality was disturbed had a longer reaction time (42.0 s) than when driving the simulator without screen interferences (18.4 s, p = 0.001). Subjects driving the simulator for a short period had the same number of symptoms as did those driving for a longer period, but had better digit symbol test results. There was no statistically significant association between the development of sickness and tank driving experience. Suggested countermeasures are expected to prevent simulator sickness among some of the simulator trainees and to make simulator training more effective.

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Spectral analysis of the electroencephalographic response to motion sickness.

Chelen WE, Kabrisky M, Rogers SK.

Air Force Institute of Technology, Wright-Patterson AFB, Dayton, Ohio.

Ten subjects participated in a laboratory experiment using cross-coupled angular stimulation to induce motion sickness symptoms. A 14-channel montage using subdermal electrodes was employed to record the electroencephalogram during a pre-Coriolis stimulation baseline through to imminent emesis. Spectral analyses of the EEG were performed upon the recorded data and individual band energies were quantified to attempt to characterize the cortical electrical response to motion sickness. Power spectral analysis was performed upon the temporo-frontal signals through the entire period over the delta, theta, and alpha EEG bands. The power in each of these bands was integrated and the baseline periods compared with that during frank sickness. Mean power spectral energy in the delta band during frank sickness increased by a factor of 13.7 over baseline. Mean theta band energy increased by a factor of 2.2. Mean alpha band energy was not significantly different. EEG power spectral levels in the delta and theta bands increased along with the level of motion sickness symptoms. These changes, particularly those in the delta band, suggest that intense low frequency oscillatory stimulation is being diffusely projected about the central nervous system. These EEG changes, similar to those sometimes seen in partial seizures, and the similarity of the symptom/sign complex in the two disorders, provide evidence that the pathophysiology and electrophysiology of motion sickness may be a variant of seizure activity.

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Motion sickness induced by sinusoidal linear acceleration in rats.

Horii A, Takeda N, Morita M, Kubo T, Matsunaga T.

Department of Otolaryngology, Osaka University Medical School, Japan.

The characteristics of linear acceleration to cause motion sickness of rats were examined using pica as a behavioral index of motion sickness. A vestibular sled was used to generate sinusoidal linear acceleration. At 0.4 Hz and with a peak acceleration of 0.15 G, the effectiveness of linear acceleration in inducing motion sickness was X-axis > Y-axis > Z-axis. At 0.4 Hz and along the X-axis, rats suffered from more severe motion sickness with a high peak G load (0.15 G) than with a low one (0.08 G). Along the X-axis and with a peak acceleration of 0.15 G, the severity of motion sickness was not related to frequency (0.4, 0.6 Hz).

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Opioid receptor involvement in the adaptation to motion sickness in Suncus murinus.

Javid FA, Naylor RJ.

The School of Pharmacy, Department of Pharmacology, University of Bradford, UK. fajavid1 bradford.ac.uk

The aim of the present study was to investigate an opioid receptor involvement in the adaptation response to motion sickness in Suncus murinus. Different groups of animals were treated intraperitoneally with either saline, morphine (0.1 and 1.0 mg/kg), naloxone (1.0, 10.0 and 5.0 mg/kg) or a combination of naloxone plus morphine in the absence or 30 min prior to a horizontal motion stimulus of 1 Hz and 40 mm amplitude. For the study of adaptation, different groups received saline on the first trial, and in subsequent trials (every 2 days) they received either saline, naloxone (1.0 and 10.0 mg/kg, i.p.) or morphine (0.1 mg/kg, i.p.) 30 min prior to the motion stimulus. Pretreatment with morphine caused a dose-related reduction in emesis induced by a single challenge to a motion stimulus. Pretreatment with naloxone alone did not induce emesis in its own right nor did it modify emesis induced by a single challenge to a motion stimulus. However, pretreatment with naloxone (5.0 mg/kg, i.p.) revealed an emetic response to morphine (P<.001) (1.0 mg/kg, i.p.) and antagonised the reduction of motion sickness induced by morphine. In animals that received saline or naloxone (1.0 mg/kg), a motion stimulus inducing emesis decreased the responsiveness of animals to a second and subsequent motion stimulus challenge when applied every 2 days for 11 trials. However, the animals receiving naloxone 10.0 mg/kg prior to the second and subsequent challenges showed no significant reduction in the intensity of emesis compared to the first trial. The data are revealing of an emetic potential of morphine when administered in the presence of a naloxone pretreatment. The administration of naloxone is also revealing of an additional inhibitory opioid system whose activation by endogenous opioid(s) may play a role in the adaptation to motion sickness on repeated challenge in S. murinus.

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[Clinical and experimental studies on royal made ping an dan in preventing motion sickness]

[Article in Chinese]

Chen KJ, Li CS, Zhang GX.

Xiyuan Hospital, China Academy of TCM, Beijing.

Royal Made Ping An Dan (PAD) is a royal clandestine prescription of the Qing Dynasty Imperial hospital for emperors, empresses, ministers, imperial maids and eunuchs. Experimental study confirmed; (1) PAD had apparent peripheral effect in inhibiting vomiting and improving mental state (P < 0.05). (2) PAD possessed markedly sedative effect (P < 0.05). (3) PAD was able to strengthen the defence ability of gastric mucosa and decreased its damage induced by chemical irritation. (4) PAD could markedly relieve the spasm of intestinal smooth muscle in vitro. (5) PAD could inhibit the growth of common pathogenic bacteria in intestine and stomach such as B. coli and B. dysenteriae. (6) The study of toxicology suggested that PAD was safe for clinical use. The clinical results showed that PAD possessed the effect in preventing 274 persons on motion sickness. The total effective rate of PAD group was 83.9%, while that of Dramamine group was 60.8%. PAD revealed better effect than that of Dramamine. Therefore, the authors realize that PAD is a better preventive drug for motion sickness.

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