Production of cutaneous analgesia by electroacupuncture in horses: variations dependent on sex of subject and locus of stimulation.

Cutaneous pain thresholds to pinprick, pinch, and heat stimuli were quantified during control and electroacupuncture trials in 23 horses. Pain thresholds for 8 areas of the body during control trials (no needles) were statistically compared with pain thresholds measured in the same areas of the same horse when given electroacupuncture treatment. Statistically significant increases of pain threshold were interpreted as induced analgesia and occurred mainly in 5 areas of the trunk, but not in the head or extremities. Analgesic efficacy varied between sexes and among 3 groups of points chosen from Chinese traditional veterinary literature. Analgesia was induced equally well in both castrated males and intact females by the electrostimulation of 5 needles inserted on the gluteal (rump) and lumbar (loins) regions. However, stimulation of 2 needles located only in the gluteal region caused a significant analgesia in females only. In contrast, stimulation of 2 needles located in the thoracic limb was analgesic in males, but infrequently so in females. Therefore, we observed differential analgesia due to an interaction between needle location and sex of subject.