Background:
Previous studies have indicated that solar and artificial ultraviolet (uv) radiation have a positive influence on psychological variables such as mood and emotional state. circulating opioid peptides have been suggested as being important in this effect.
Objectives:
To investigate in a controlled trial the influence of uva radiation on opioid peptide levels.
Methods:
We determined plasma levels of beta-endorphin immunoreactive material (irm) and met-enkephalin in uv-exposed (n = 35) and non-exposed (n = 9) healthy volunteers. on the first day of the study, blood samples were taken from the volunteers (time a). uva irradiation was subsequently administered with an air-conditioned tanning device. during the uv exposures the volunteers wore opaque goggles. twenty minutes after uv exposure, blood samples were collected again (time b). within the following 3 weeks the volunteers had a series of five uv exposures. on the last day of the study (24 h after the sixth uv exposure) blood samples were collected (time c). the cumulative uva doses were 96 j cm-2 for skin type ii and 126 j cm-2 for skin type iii. the controls had no uv exposures. plasma beta-endorphin irm and met-enkephalin levels were determined using radioimmunoassays.
Results:
At all times of blood collection (a, b, c), there were no significant differences in plasma levels of beta-endorphin irm and met-enkephalin between uv-exposed and non-exposed volunteers (p > 0.05).
Conclusions:
Uva irradiation does not significantly elevate plasma levels of beta-endorphin irm and met-enkephalin. therefore we suggest that psychological benefits claimed to occur after uv exposure are unlikely to be mediated by the types of circulating opioid peptides measured in this study.