[Plasma beta-endorphins under the effect of pain stimulus. Preliminary report]

Using a diagnostic kit N.E.N. (USA) the authors investigated beta-endorphin-like immunoreactivity in the plasma of young, healthy subjects. It was found that the level of beta-endorphin determined in this way in 10 subjects ranged from 15 to 120 pgml-1 and showed relatively constant values in two determinations carried out at an interval of one hour. Psychological tests showed that subjects with low beta-endorphin level had a low neuroticism index and extra-version, while in the subjects with high beta-endorphin level the neuroticism index was high and introversion features were more prevalent. After application of a painful stimulus (ischaemic test) the level of beta-endorphin changed in most subjects increasing or decreasing. The comparison of the differences in the levels of beta-endorphin immediately before and after the test for pain tolerance suggests that the higher was this difference the lower was pain tolerance and conversely.