Molecular classification of the placebo effect in nausea

In this proof-of-concept study, we tested whether placebo effects can be monitored and predicted by plasma proteins. In a randomized controlled design, 90 participants were exposed to a nauseating stimulus on two separate days and were randomly allocated to placebo treatment or no treatment on the second day. Significant placebo effects on nausea, motion sickness, and (in females) gastric activity could be verified. Using label-free tandem mass spectrometry, 74 differentially regulated proteins were identified as correlates of the placebo effect. Gene ontology (GO) enrichment analyses identified acute-phase proteins and microinflammatory proteins to be involved, and the identified GO signatures predicted day-adjusted scores of nausea indices in the placebo group. We also performed GO enrichment analyses of specific plasma proteins predictable by the experimental factors or their interactions and identified 'grooming behavior' as a prominent hit. Finally, Receiver Operator Characteristics (ROC) allowed to identify plasma proteins differentiating placebo responders from non-responders, comprising immunoglobulins and proteins involved in oxidation reduction processes and complement activation. Plasma proteomics is a promising tool to identify molecular correlates and predictors of the placebo effect in humans.

[Anti-motion sickness efficacy of the extracted mixture of Chinese medical herbs and its influence on the blood level of hormones]

OBJECTIVE

To investigate the anti-motion sickness efficacy and influence on the blood level of some hormones of a Chinese prescription composed of 10 herbs such as spina date seed.

METHODS

According to the report by Cramptom and Lucot, SD rats and Beagle dogs were rotated around a horizontal axis, and the rat behavior of pica for Kaolin and the latency to vomit in dog were observed. In addition, guinea pigs were rotated around a vertical axis, and the nystagmus was recorded. Blood levels of corticosterone, adrenocorticotrophic hormone (ACTH), corticotropin releasing hormone (CRH) and arginine vasopressin (AVP) in rats were measured with radioimmunoassay. The influences of the extracted mixture of herbs on these variables were simultaneously investigated.

RESULTS

Compared with control group, oral administration of the extracted mixture of herbs: (1) significantly inhibited the rat behavior of pica for Kaolin and prolonged the latency to vomit in dog dose-dependently; (2) decreased the frequency of nystagmus and mean slow phase speed in rat; (3) reduced the elevation of corticosterone, ACTH, CRH and AVP in rat blood induced by rotatory stimulation; and (4) these effects of the extracted mixture of herbs were almost identical to dimenhydrinate.

CONCLUSION

(1) The extracted mixture of Chinese Medicinal Herbs we used could inhibit motion sickness effectively. (2) This drug could reduce the blood levels of hormones of hypothalamic-pituitary-adrenocortical axis and AVP elevated by provocative rotatory stimulation.

Serum levels of immunoglobulins (IgG, IgA, IgM) in Antarctic summer expeditioners and their relationship with seasickness

The Antarctic continent is full of environmental extremes like isolation, cold, UV exposure, and blizzards etc. The present study was conducted to analyze the effect of ship borne journey and the impact of Antarctic harsh environment on serum immunoglobulin (IgG, IgM, IgA) levels and their relationship with seasickness in Indian expeditioners. It was observed that one month onboard ship journey induced an increase in serum IgA levels and decrease in IgG levels while after being one month off board at the Indian research station Maitri, decreased levels of IgG and increased levels of IgA were found. IgM levels were not altered in comparison to the base line control. Moreover, serum IgG level showed a positive correlation while IgA level showed a negative correlation with seasickness. The stimulation of human peripheral blood mononuclear cells (PBMCs) with serum of expeditioner at different places showed that IgA at lower dose induces the release of pro-inflammatory IL-1β, and IL-6 cytokines from PBMCs while higher dose of IgA decreases proinflammatory cytokine production. The release of anti-inflammatory cytokines TGF-β1 and IL-10 was not significantly altered. Thus, the present study concluded that ship borne journey and Antarctic environment lead to increased serum IgA levels while decreased IgG levels. It also suggests that serum IgA level could be a possible biomarker for environmental stress.

Motion sickness, stress and the endocannabinoid system

Background

A substantial number of individuals are at risk for the development of motion sickness induced nausea and vomiting (N&V) during road, air or sea travel. Motion sickness can be extremely stressful but the neurobiologic mechanisms leading to motion sickness are not clear. The endocannabinoid system (ECS) represents an important neuromodulator of stress and N&V. Inhibitory effects of the ECS on N&V are mediated by endocannabinoid-receptor activation.

Methodology/Principal Findings

We studied the activity of the ECS in human volunteers (n = 21) during parabolic flight maneuvers (PFs). During PFs, microgravity conditions (<10⁻² g) are generated for approximately 22 s which results in a profound kinetic stimulus. Blood endocannabinoids (anandamide and 2-arachidonoylglycerol, 2-AG) were measured from blood samples taken in-flight before start of the parabolic maneuvers, after 10, 20, and 30 parabolas, in-flight after termination of PFs and 24 h later. Volunteers who developed acute motion sickness (n = 7) showed significantly higher stress scores but lower endocannabinoid levels during PFs. After 20 parabolas, blood anandamide levels had dropped significantly in volunteers with motion sickness (from 0.39±0.40 to 0.22±0.25 ng/ml) but increased in participants without the condition (from 0.43±0.23 to 0.60±0.38 ng/ml) resulting in significantly higher anandamide levels in participants without motion sickness (p = 0.02). 2-AG levels in individuals with motion sickness were low and almost unchanged throughout the experiment but showed a robust increase in participants without motion sickness. Cannabinoid-receptor 1 (CB1) but not cannabinoid-receptor 2 (CB2) mRNA expression in leucocytes 4 h after the experiment was significantly lower in volunteers with motion sickness than in participants without N&V.

Conclusions/Significance

These findings demonstrate that stress and motion sickness in humans are associated with impaired endocannabinoid activity. Enhancing ECS signaling may represent an alternative therapeutic strategy for motion sickness in individuals who do not respond to currently available treatments.

Plasma vasopressin, an etiologic factor of motion sickness in rat and human?

Arginine vasopressin (AVP) is considered as an etiologic hormone in motion sickness. However, the possible role of plasma AVP in motion sickness is still controversial. A number of studies have found a gender difference in susceptibility to motion sickness in humans and experimental animals, with female subjects being more susceptible. However, the existence of a gender difference in the AVP response to motion sickness is not known. This study was designed to verify the assumption that plasma vasopressin plays a role in motion sickness. Changes in plasma vasopressin were observed after motion sickness-inducing rotatory stimuli in both sexes in human subjects and rats receiving or not anti-motion-sickness treatments. Plasma vasopressin levels in motion sickness rats exhibited a decrease after rotation in female, but not in male rats. The vasopressin content of the pituitary increased in both sexes. Plasma vasopressin in rats of both sexes tended to increase after a 15-day adaptive training of rotation, but pituitary vasopressin content was not affected under this condition. In contrast, in human subjects, plasma vasopressin levels increased after rotation in all males, but not in females. When anti-motion-sickness drugs (domperidone 10 mg + flunarizine 5 mg) were administered, plasma vasopressin levels were elevated in both females and males. It is concluded that plasma vasopressin increases after motion sickness-induced stimulation provided subjects have become trained to motion sickness. These results do not support an etiologic role of plasma vasopressin in the genesis of motion sickness.

[Image and quantity analysis of prostaglandin in rats' blood plasma and Na(+)-K(+)-ATPase in their cerebellum during the prevention of motion sickness by cinnarizine]

To study the mechanism of cinnarizine in preventing motion sickness, TXB2, 6-Keto-PGF1 alpha in rats' blood plasma and Na(+)-K(+)-ATPase activity in the endothelial cells of their cerebellar capillary were measured and analysed by a radioactive immunity analyser and a computer image system. The results showed that TXB2 and 6-Keto-PGF1 alpha in rats' blood plasma in the cinnarizine preventing group (CPG) decreased remarkably, compared with those in the motion sickness group(MSG) (p < 0.05). The activity of Na(+)-K(+)-ATPase in the endothelial cells of rats' cerebellar capillary in CPG was higher than that in MSG (p < 0.01). The authors suggest that the lower concentration of TXB2 and 6-Keto-PGF1 alpha in rats' blood plasma in CPG is closely related to cinnarizine which prevents Ca2+ from entering into the platelets and into the endothelial cells of blood vessels. The higher activity of Na(+)-K(+)-ATPase in the cerebellum may be caused by cinnarizene which dilates the blood vessels in the brain, increases the blood flow therein, and hinders Ca2+ from getting into the cerebellum cells. These change are believed to be the important mechanism of how cinnarizine prevents motion sickness.

Space sickness and fluid shifts: a hypothesis

In a sample of 64 first-time Space Shuttle crew members, 9 preflight variables related to fluid, electrolyte, and cardiovascular status were previously found to be significantly related to space sickness. The nine variables are serum uric acid, red cell count, environmental temperature at the launch site, serum phosphate, urine osmolality, serum thyroxine, sitting systolic blood pressure, calculated blood volume, and serum chloride. Using discriminant analysis, these preflight variables were used to correctly classify the 64 astronauts according to their space sickness incidence (NOTSICK or SICK) with 80% success, using two methods of pseudo-crossvalidation. Symptoms of motion sickness may be induced on Earth, either with a sufficiently high level of vestibular stimulation or with less vestibular stimulation after reducing the threshold for motion sickness induction. Some of the nine predictor variables support a fluid shift hypothesis of space sickness etiology by which central volume expansion in weightlessness may lower the threshold required for novel vestibular stimulation to cause space sickness. According to this hypothesis, some astronauts suffer a greater central volume expansion than do others, causing them to have greater physiologic responses to fluid shifts, which, in turn, proportionally reduces their threshold for induction of space sickness. The hypothesis is supported by preflight and postflight echocardiographic comparisons of heart volumes in 19 shuttle astronauts. The postflight left ventricular diastolic volume index was decreased by 34 +/- 3% in the astronauts with MODERATE or SEVERE space sickness, but only 9 +/- 5% (P < .05) in the NONE or MILD group, indicating that an exaggerated physiologic adaptation to fluid shifts is associated with space sickness.

Autonomic function and plasma catecholamines following stressful sensory stimuli

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.

beta-Endorphin and arginine vasopressin following stressful sensory stimuli in man

This experimentation partially defines, for the first time, the response of beta-endorphin (ENDO) in man during tests designed to elicit nausea and motion sickness. These responses are similar to those associated with arginine vasopressin (AVP) and adrenocorticotropin (ACTH) to the extent that all hormones rise in response to motion sickness (p < 0.003). Repeated exposure diminished motion-induced release of ENDO (p < 0.005) and AVP (p < 0.004) despite a three-fold increase in resistance to motion stimuli. Higher post-stress levels of AVP (p < 0.04) and ACTH (p < 0.02) were correlated with greater resistance to motion sickness. These data support the hypothesis that release of AVP is a significant link between stressful motion and motion-induced nausea and other autonomic system changes. Further, resistant individuals apparently can tolerate higher peripheral levels of AVP before nausea results. Peripheral release of ENDO and ACTH may follow release of AVP; however, given the extensive and complex functional interactions that exist between AVP and the opiate systems, it is not yet possible to define a clear role for ENDO in the etiology of motion sickness.

Histaminergic response to Coriolis stimulation: implication for transdermal scopolamine therapy of motion sickness

The blood levels of histamine and 5-hydroxytryptamine (5-HT) in 10 subjects, with or without administration of the transdermal therapeutic system of scopolamine (TTS-S), were measured following motion sickness (MS) induced by Coriolis stimulation. Histamine and 5-HT were assayed using the fluorometric method. The results demonstrated that the blood levels of histamine increased significantly following MS and were even higher in the subjects using TTS-S, but we found neither significant changes in the blood levels of 5-HT following MS nor any effect of TTS-S on it. The results suggest that histamine contributes to the development of MS, and scopolamine may exert its anti-MS action by affecting the histaminergic system as well as the acetylcholinergic system; there may not be a definite relation between 5-HT and the development of MS.

Vasopressin and oxytocin responses to illusory self-motion and nausea in man

Vasopressin and oxytocin are nonapeptides secreted from the neurohypophysis; increases in vasopressin are associated with nausea and vomiting in some, but not all, species. Our aim was to determine whether plasma vasopressin and oxytocin levels were altered in healthy volunteers who did or did not develop nausea during vection, an optokinetic stimulus which produces the illusion of self-motion. Vection was produced by rotating a drum with an inner surface of black and white vertical stripes around the seated stationary subject. Gastric myoelectrical activity was recorded continuously throughout the experiment with electrodes positioned on the abdominal surface. Plasma samples were obtained before vection and after drum rotation stopped when nausea and tachygastria were present. Vasopressin and oxytocin were extracted from plasma and quantified by RIA. During vection six subjects reported nausea and developed gastric dysrhythmias; six other subjects had no nausea and remained in normal 3-cpm myoelectrical rhythms. Vasopressin and oxytocin values before vection were similar in each group of subjects. One minute after vection stopped, plasma vasopressin levels were significantly greater (P less than 0.05) in subjects experiencing nausea and tachygastrias (35.4 +/- 26.7 pmol/L) than in those without symptoms (2.7 +/- 0.47 pmol/L). Oxytocin levels were unchanged by either vection or nausea. It is concluded that 1) vasopressin, not oxytocin, neurons in the magnocellular-neurohypophyseal system are activated during vection-induced nausea and gastric dysrhythmias; and 2) illusory self-motion may be used safely to study the neuroendocrine responses to brain-gut interactions and nausea in man.

[Transdermal therapeutic system of scopolamine (TTS-S) in the prevention of sea sickness and its mechanism of action]

The efficacy of transdermal therapeutic system of scopolamine (TTS-S) in the prevention of sea sickness and the extent of its side effects were evaluated in 130 male healthy sailors (volunteers) in a placebo-controlled, double-blind, randomized study. TTS-S or transdermal placebo (TD-P) were placed behind ears 12 hours before departure and removed 72 hours later. It was found that the severity of motion sickness in the TTS-S group was significantly milder than that in the TD-P group. The TTS-S had no statistically significant side effects when compared with the TD-P. The levels of histamine in the blood of 10 subjects, with or without TTS-S, were measured following experimental motion sickness induced by Coriolis test, and the induced optokinetic rotational nystagmus was recorded. The results demonstrated that the level of blood histamine increased after motion sickness, it was higher in the subjects with TTS-S, and there was no significant difference for the optokinetic rotational nystagmus between groups. These findings suggested that histamine contribute to the development of motion sickness and scopolamine may play anti-motion sickness action by blocking the H1-receptor.

Hormonal changes after parabolic flight: implications on the development of motion sickness

Twenty-two different humoral parameters including stress-, gastrointestinal- and volume-regulating hormones were measured before and within 45 min after parabolic flight maneuvers of twenty healthy adult subjects. We compared hormonal data of motion sickness-affected participants with those unaffected. Changes in cortisol and vasoactive intestinal peptide plasma levels were significantly different (p less than 0.002 and p less than 0.004) between the two groups with increasing plasma levels of both hormones during motion sickness but decreasing levels within the control group. Growth hormone and prolactin plasma levels increased by 400% and 115% within the motion sickness-affected group and to a smaller degree (120% and 40% increases, respectively) within the control group, while ACTH levels were almost unchanged within both groups. Pancreatic polypeptide and gastrin plasma levels as well as plasma levels of insulin and C-peptide were significantly decreased within both groups after the parabolic flight. Plasma renin, aldosterone, atrial natriuretic peptide and cyclic GMP levels were unchanged within the control group. Within the motion sickness-affected group, plasma renin and aldosterone levels were decreased and atrial natriuretic peptide levels increased after the flight. Humoral parameters of the thyroid gland were neither changed within the groups nor different between the groups. The present data confirm previous results that increases in plasma levels of certain stress hormones participate in motion sickness. Furthermore, increases in vasoactive intestinal peptide levels participate in motion sickness. These increases could explain some of the gastrointestinal symptoms in motion sickness and might serve as markers for a discrimination between regular stress and motion sickness.

[Circulation and oxygen tension in the brain of the alert rabbit during motion sickness]

Sea sickness in alert rabbits induced an increase in the local blood flow in frontal, occipital and temporal cortex as well as an increase of the total blood flow in the brain. The blood flow increases first in the temporal cortex. The changes occur at an unaltered pO2 level in the brain cortex and hypotensive response. The blood flow increase seems to be due to reflex dilatory effects of the vestibular apparatus on the brain vessels and to intensification of metabolism in result of general activation of cortical structures.

[Content of biogenic amines and their precursors in human blood during head-down tilt and in taking pharmacological agents to prevent the motion sickness syndrome]

The 6-hour exposure to head-down tilt at --15 degrees was accompanied by an increased blood content of adrenaline and noradrenaline, thus indicating the activation of the sympathoadrenal system. The catecholamine concentration was shown to be proportional to the head-down tilt time. The exposure also led to an increase of the content of serotonin and left the content of 5-hydroxytryptophan, tryptophan, histamine and histidine unchanged. After administration of ephedrine and especially, ephedrine in combination with pipolphen the increase in the concentration of catecholamines and serotonin became significantly less pronounced.

Increased secretion of growth hormone, prolactin, antidiuretic hormone, and cortisol induced by the stress of motion sickness

The stress of motion sickness was experimentally provoked by Coriolis effect. Significant and reproducible increases from the basal serum level (delta mean +/- S.E.) of antidiuretic hormone delta - ADH: 48.2 +/- 4.6 pg/ml; p less than 0.0005), of growth hormone (delta - hGH: 10.0 +/- 1.2 ng/ml; p less than 0.0005), of prolactin (delta - hPRL: 186.5 +/- 29.9 muU/ml; p less than 0.0005), and of cortisol (delta - F; 12.3 +/- 0.9 microgram%; p less than 0.0005) were observed, whereas the luteinizing hormone levels did not change significantly. The stimulation of hormone secretion induced by different degrees of motion sickness seems to correlate with the severity of motion sickness. The secretion of antidiuretic hormones is the most sensitive indicator for the stress of motion sickness whereas growth hormone, prolactin, and cortisol responses to the stress of motion sickness are more delayed and less pronounced.

Increased urinary excretion of triiodothyronine (T3) and thyroxine (T4) and decreased serum thyreotropic hormone (TSH) induced by motion sickness

We exposed 35 male subjects to a rotary chair and motion sickness was provoked by Coriolis effect. This stress caused an increased excretion of urinary T3 and T4 and a decrease of TSH levels in serum. The increment in urinary excretion of thyroid hormones may serve as a very useful measure for the quantitation of physical stress. Although no statistically significant change of T3, T4, and TBG levels in serum could be observed by the employed techniques, the hypothesis is favoured that motion sickness probably causes an immeasurably small increase of the free thyroid hormone fraction in serum, thereby increasing urinary excretion of T3 and T4 and, in turn, decreasing TSH secretion. Physical or psychological stress situations involve most of the endocrine systems. Contadictory results have been reported in the literature concerning the relationship between thyroid function and stress.