[Individual differences in the sensitivity to the effect of alcohol upon pain].

In this study, the relationship between pain threshold and blood ethanol level, and also the effect of alcohol sensitivity upon the threshold was investigated. Thirty-one healthy subjects, aged 20 to 62 years, were studied. The genotypes at the aldehyde dehydrogenase 2 (ALDH) locus were determined in each subject to evaluate the alcohol sensitivity. The subjects were divided into three groups based on the ALDH2 genotypes, i.e., the ALDH2*1/1 (homozygous active ALDH), the ALDH21/2 (heterozygous inactive ALDH) and the ALDH22/2 (homozygous inactive ALDH). The subjects were given orally 0.4 g.kg-1 and/or 0.8 g.kg-1 of ethanol. Venous blood samples were collected at 30, 60, 120, 180, and 240 min after ethanol intake and blood ethanol and acetaldehyde levels were determined. Prior to the ethanol intake and at each sampling of the blood, the pain thresholds were measured by three stimulating methods, i.e., a mechanical method (algometer), a thermal method (Nakahama's pain meter NYT-5) and a chemical method (potassium iontophoretic meter). In the ALDH21/1 and ALDH21/2 groups, the pain threshold measured by the three methods increased with the elevation of blood ethanol levels, especially the threshold by the mechanical method showed clear rise with blood ethanol level. The subjects who belonged to the ALDH22/*2 group showed a high blood acetaldehyde level and various psychophysical symptoms. The results of the three tests had no relationships with the variation of blood ethanol levels.