Abstract
Many studies have demonstrated sex and age differences in motion sickness, but the underlying physiological basis is still in controversy. In the present study, we tried to investigate the potential correlates of endocrine and/or neuronal activity with sex and age differences in rats with motion sickness. LiCl-induced nausea symptom was evaluated by conditioned gaping. Motion sickness was assessed by measurement of autonomic responses (i.e., conditioned gaping and defecation responses), motor impairments (i.e., hypoactivity and balance disturbance) after Ferris wheel-like rotation, and blood hormone levels and central Fos protein expression was also observed. We found that rotation-induced conditioned gaping, defecation responses and motor disorders were significantly attenuated in middle-aged animals (13- and 14-month-age) compared with adolescents (1- and 2-month-age) and young-adults (4- and/or 5-month-age). LiCl-induced conditioned gapings were also decreased with age, but was less pronounced than rotation-induced ones. Females showed greater responses in defecation and spontaneous locomotor activity during adolescents and/or young-adult period. Blood adrenocorticotropic hormone and corticosterone significantly increased in 4-month-old males after rotation compared with static controls. No significant effect of rotation was observed in norepinephrine, epinephrine, β-endorphin and arginine-vasopressin levels. The middle-aged animals (13-month-age) also had higher number of rotation-induced Fos-labeled neurons in the spinal vestibular nucleus, the parabrachial nucleus (PBN), the central and medial nucleus of amygdala (CeA and MeA) compared with adolescents (1-month-age) and young-adults (4-month-age) and in the nucleus of solitary tract (NTS) compared with adolescents (1-month-age). Sex difference in rotation-induced Fos-labeling was observed in the PBN, the NTS, the locus ceruleus and the paraventricular hypothalamus nucleus at 4 and/or 13 months of age. These results suggested that the sex and age differences in motion sickness may not correlate with stress hormone responses and habituation. The age-dependent decline in motion sickness susceptibility might be mainly attributed to the neuronal activity changes in vestibulo-autonomic pathways contributing to homeostasis regulation during motion sickness.
Highlights
Motion sickness is a common disorder induced by provocative motion of transports and simulators or by weightlessness and virtual reality (Golding and Gresty, 2015)
The number of Fos labeling (Fos-LI) neurons was counted under a light microscope by a rater who was unaware of the experimental conditions of the rats and the photographs were taken with a digital camera
The present study revealed that both LiCl injection and rotation stimulation significantly induced conditioned gaping in both male and female animals, but no significant sex differences were found when females were not in menstruation phase
Summary
Motion sickness is a common disorder induced by provocative motion of transports and simulators or by weightlessness and virtual reality (Golding and Gresty, 2015). Accumulating evidence indicates that sex and age are two main predictors of motion sickness susceptibility in general populations (Golding, 2006). Evidence-based clinical investigations showed that female gender was a strong risk factor for chemotherapyinduced and postoperative nausea and vomiting (Golding, 2006; Jordan et al, 2014). These observations seem to suggest that there must be anatomical and/or physiological basis underlying high motion sickness susceptibility in females. Whether the age-related decline in motion sickness susceptibility can be attributed to habituation induced by repeated motion exposure during aging is still unclear
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
