Table 1.
Stress and nausea during the experiment.
Table 2.
Demographic data.
Figure 1.
Whole blood endocannabinoid concentrations during a parabolic flight experiment in 21 male volunteers.
Panel A compares blood concentrations of the endocannabinoid anandamide between volunteers who developed motion sickness accompanied by severe N&V (n = 7, red lines) and those who did not (n = 14, blue lines). After the 10th parabolic maneuver (T1), anandamide blood concentrations dropped in individuals with motion sickness but increased in volunteers without (Mann-Whitney U Statistic = 14.5, T = 42.5, *p = 0.02). After the 20th maneuver (T2), this difference remained significant (Mann-Whitney U Statistic = 14.0, T = 42.0, *p = 0.01). Panel B shows the same comparison with regard to the endocannabinoid 2-AG. 2-AG values in volunteers with motion sickness remained almost constant and non-reactive but increased in individuals without. *indicates significantly higher 2-AG blood concentrations in individuals without motion sickness after termination of parabolic maneuvers (Mann-Whitney U Statistic = 0.0, T = 85.0, p = 0.04).
Figure 2.
Comparison of leukocyte cannabinoid receptor mRNA between volunteers with and without motion sickness during the parabolic flight experiment.
RNA was prepared from whole blood and subjected to quantitative RT-PCR (triplicate determinations). Data were calculated relative to GAPDH and RPL13A-mRNA using an efficiency-corrected algorithm. *indicates a significant decline in CB1-receptor mRNA (W = −26.0, T+ = 1.0, T- = −27.0, p = 0.03, Wilcoxon Signed Rank Test) in volunteers with motion sickness when compared to 24 h pre-flight values. CB1-receptor mRNA in individuals without motion sickness remained unchanged over time (W = −8.0, T+ = 10.0, T- = −18.0, p = 0.58) as was CB2-receptor expression before and after the experiment. Horizontal black bars in the boxplots indicate median values; upper and lower lines of the boxes show the 5th and 95th percentile.
Figure 3.
Saliva cortisol levels and 2-AG blood concentrations in volunteers with and without motion sickness.
Panel A shows the inverse relationship between blood concentrations of the endocannabinoid 2-AG and saliva cortisol in participants without motion sickness. The increase in 2-AG during the parabolic maneuvers was associated with low saliva cortisol concentrations. *indicates significantly higher 2-AG concentrations in volunteers without motion sickness (s. Figure 2). Panel B illustrates the opposite association between 2-AG concentrations and saliva cortisol in volunteers with motion sickness. These individuals had low blood 2-AG levels and high saliva cortisol values. #indicates significantly higher saliva cortisol concentrations in participants with motion sickness (p<0.01, t-test).