Plasma cortisol and beta-endorphin in horses subjected to electro-acupuncture for cutaneous analgesia.

The research suggests that performing electro-acupuncture on horses led to a rise in plasma levels of beta-endorphin and cortisol, but this increase did not consistently correspond to the degree of pain relief. Also, the rates of respiration and heart were considerably amplified during electro-acupuncture treatment. No measurable factors before or during treatment explained why pain relief differed depending on the gender of the horse and stimulation location.

Research methodology

• The study focused on the impact of electro-acupuncture (EA) on horses, particularly in inducing cutaneous analgesia or relieving skin-related pain.
• During this investigation, a number of factors were observed such as plasma concentrations of beta-endorphin (beta-EP) and cortisol, heart and respiration rates, as well as the packed cell volume and plasma total protein in both intact female horses and castrated male horses.

Key findings

• The research found that EA treatment led to an increase in plasma beta-EP and cortisol levels. Despite this, there was no consistent relationship between the magnitude of these increases and the degree of analgesia induced by EA, suggesting these hormone levels may not directly influence the effectiveness of EA as a pain relief treatment.
• Heart and respiration rates also increased significantly during the EA treatment, which may suggest a physiological stress response to the treatment, or could be an effect of the pain relief itself.
• Female horses exhibited higher packed cell volume and plasma beta-EP levels, and lower plasma total protein than castrated male horses. However, the significance of these differences and how they influence EA efficacy remains unclear.
• No significant differences were found between male and female horses in terms of cortisol levels, heart rate and respiration rate.
• The paper acknowledges that none of the parameters measured in this study could explain the differences in analgesic effect based on the sex of the horse or the location of the stimulation.

Implications and conclusions

• The research provides insight into the physiological changes in horses undergoing EA treatment, but it does not conclusively explain why the analgesic effects of EA vary based on sex or location of stimulation.
• These findings suggest a complex relationship between the biological responses of horses to EA and the overall efficacy of the treatment in managing pain. This suggests further research is needed in this area to fully understand the impact and efficacy of EA treatment in horses.