The influence of 1,3,7-trimethyl-xanthine (caffeine) on the pain-caused dilation of pupil.
The pupil dilation in man caused by pain was investigated. The pain stimulus was induced electrically. The size of the pupil was measured according to the "flying spot scanning method". The accuracy of measurement was increased by computer-assisted addition of repeated responses as well as by elimination of the, usually not considered constriction due to light compensation over Maxwellian view. The pure psycho-sensory dilation shows no initial contraction. The central stimulant 1,3,7-trimethyl-xanthine (caffeine) does not influence the course and adaption of the pupil reaction by a pain stimulus over the threshold. The pupil reaction correlates with the subjective feeling of pain. This suggests that caffeine does not influence the feeling of pain.
D000328:Adult; D002110:Caffeine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010146:Pain / Q000503:physiopathology*; D011680:Pupil / Q000187:drug effects*; D013997:Time Factors
D002110:Caffeine