The comparison of sensitivity of motion sickness between retinal degeneration fast mice and normal mice

Evaluating proxies for motion sickness in rodent

Motions sickness (MS) occurs when the brain receives conflicting sensory signals from vestibular, visual and proprioceptive systems about a person's ongoing position and/or motion in relation to space. MS is typified by symptoms such as nausea and emesis and implicates complex physiological aspects of sensations and sensorimotor reflexes. Use of animal models has been integral to unraveling the physiological causality of MS. The commonly used rodents (rat and mouse), albeit lacking vomiting reflex, reliably display phenotypic behaviors of pica (eating of non-nutritive substance) and conditioned taste aversion (CTAver) or avoidance (CTAvoi) which utilize neural substrates with pathways that cause gastrointestinal malaise akin to nausea/emesis. As such, rodent pica and CTAver/CTAvoi have been widely used as proxies for nausea/emesis in studies dealing with neural mechanisms of nausea/emesis and MS, as well as for evaluating therapeutics. This review presents the rationale and experimental evidence that support the use of pica and CTAver/CTAvoi as indices for nausea and emesis. Key experimental steps and cautions required when using rodent MS models are also discussed. Finally, future directions are suggested for studying MS with rodent pica and CTAver/CTAvoi models.

A New Vestibular Stimulation Mode for Motion Sickness With Emphatic Analysis of Pica

Motion sickness (MS) was frequently introduced for rodents in research work through passive motion that disturbed vestibular signals in the presence of visual and aleatory, proprioceptive inputs. Inducement of MS in this way causes conflicting signals that activate intermixed neural circuits representing multimodal stimulation. From reductionism, a lab setup to elicit rat MS via vestibular stimulation was configured in the present study for MS study in connection with dissection of the central vestibular component causally underlying MS. The individual animal was blinded to light with a custom-made restrainer, and positioned at an inclination of 30° for otolith organs to receive unusual actions by gravitoinertial vector. Following a 2-h double-axis (earth-vertical) rotation involving angular acceleration/deceleration, a suit of behaviors characterizing the MS was observed to be significantly changed including pica (eating non-nutritive substance like kaolin), conditioned taste avoidance and locomotion (p < 0.05). Notably, for the statistical hypothesis testing, the utility of net increased amount of kaolin consumption as independent variables in data processing was expounded. In addition, Fos-immunostained neurons in vestibular nucleus complex were significantly increased in number, suggesting the rotation-induced MS was closely related to the vestibular activation. In conclusion, our work indicated that the present setup could effectively elicit the MS by disturbing vestibular signals in rat in the context of well-controlled proprioceptive inputs and lack of visual afference.

Phencynonate S-isomer as a eutomer is a novel central anticholinergic drug for anti-motion sickness

To compare and evaluate the differences of stereoselective activity, the binding affinity, metabolism, transport and molecular docking of phencynonate isomers to muscarinic acetylcholine receptor (mAChR) were investigated in this study. The rotation stimulation and locomotor experiments were used to evaluate anti-motion sickness effects. The competitive affinity with [³H]-QNB and molecular docking were used for studying the interactions between the two isomers and mAChR. The stereoselective mechanism of isomers was investigated by incubation with rat liver microsomes, a protein binding assay and membrane permeability assay across a Caco-2 cell monolayer using a chiral column HPLC method. The results indicated that S-isomer was more effective against motion sickness and had not anxiogenic action at therapeutic doses. S-isomer has the higher affinity and activity for mAChR in cerebral cortex and acted as a competitive mAChR antagonist. The stereoselective elimination of S-isomer was primarily affected by CYP1B1 and 17A1 enzymes, resulting in a higher metabolic stability and slower elimination. Phencynonate S isomer, as a eutomer and central anticholinergic chiral drug, is a novel anti-motion sickness drug with higher efficacy and lower central side effect. Our data assisted the development of a novel drug and eventual use of S-isomer in clinical practice.

Optical Illusions and Spatial Disorientation in Aviation Pilots

Optical illusions are involved in the perception of false or erroneous images which might involve disorientation. They occur by a discordance by the peripheral systems about the information captured and generally, resulting in pilots failure to recognize key signals. The aim of this study is to review the state of the art of spatial disorientation and optical illusions in aviation pilots. This kind of disorientation has important practical consequences, because a remarkable percentage of plane accidents are related to pilot's optical illusions. An exhaustive review using pubmed and semantic scholar databases was conducted to find out the most frequent optical illusions in aviation pilots. A total of 45 full text articles published English or Spanish were reviewed. To our knowledge, this is the first study to review exhaustively and describe the main factors involved in spatial disorientation and optical illusions affecting aviation pilots. Mainly, contextual factors: width of landing track lights, nocturnal operations or low visibility, inclination of the landing track, decline of the ground, size of habitual references, low level approach on the water, black hole, sky/terrain confusion, distortion by climatic factors, autokinesis or autocinetics, optional investment illusion, illusions by vection, false horizon, rain on the windshield, misalignment in the approach, vibrations, somatogravic illusion, coriolis illusion and "G" forces. In a lesser extent, human factors and pathologies of the visual systems involved in spatial disorientation and associated optical illusions affecting aviation pilots are also described.

DISCUSSION

Practical implications are further discussed.

The Combination of Scopolamine and Psychostimulants for the Prevention of Severe Motion Sickness

BACKGROUND AND AIMS

Severe motion sickness is a huge obstacle for people conducting precise aviation, marine or emergency service tasks. The combination of scopolamine and d-amphetamine is most effective in preventing severe motion sickness. However, this combination is not included in any present pharmacopoeia due to the abuse liability of d-amphetamine. We wanted to find a combination to replace it for the treatment of severe motion sickness.

METHODS AND RESULTS

We compared the efficacy of scopolamine, diphenhydramine, and granisetron (representing three classes of drugs) with different doses, and found that scopolamine was the most effective one. We also found scopolamine inhibited central nervous system at therapeutic doses and caused anxiety. Then, we combined it with different doses of psychostimulants (d-amphetamine, modafinil, caffeine) to find the best combination for motion sickness. The efficacy of scopolamine with modafinil (1 + 10 mg/kg) was equivalent to that of scopolamine with d-amphetamine (1 + 1 mg/kg); This combination also excited central nervous system and abolished the anxiety caused by scopolamine.

CONCLUSIONS

The optimal dose ratio of scopolamine and modafinil is 1:10. This combination is beneficial for motion sickness and can abolish the side effects of scopolamine. So, it might be a good replacement of scopolamine and d-amphetamine for severe motion sickness.