Cutaneous analgesia, hemodynamic and respiratory effects, and β-endorphin concentration in spinal fluid and plasma of horses after acupuncture and electroacupuncture

Abstract

Objective - To determine cutaneous analgesia, hemodynamic and respiratory effects, and β-endorphin concentration in spinal fluid and plasma of horses after acupuncture and electroacupuncture (EA). Animals - 8 healthy 10- to 20-year-old mares that weighed between 470 and 600 kg. Procedure - Each horse received 2 hours of acupuncture and 2 hours of PAES at acupoints Bladder 18, 23, 25, and 28 on both sides of the vertebral column as well as sham needle placement (control treatment). Each treatment was administered in a random order. At least 7 days elapsed between treatments. Nociceptive cutaneous pain threshold was measured by use of skin twitch reflex latency (STRL) and avoidance to radiant heat (≤ 50°C) in the lumbar area. Skin temperature, cardiovascular and respiratory variables, and β-endorphin concentration in spinal fluid (CSF-EN) and plasma (plasma-EN) were measured. Results - Acupuncture and PAES significantly increased STRL and skin temperature. The CSF-EN was significantly increased from baseline values 30 to 120 minutes after onset of PAES, but it did not change after acupuncture and control treatments. Heart and respiratory rates, rectal temperature, arterial blood pressure, Hct, total solids and bicarbonate concentrations, base excess, plasma-EN, and results of blood gas analyses were not significantly different from baseline values after acupuncture, PAES, and control treatments. Conclusions and Clinical Relevance - Administration of PAES was more effective than acupuncture for activating the spinal cord to release β-endorphins into the CSF of horses. Acupuncture and PAES provided cutaneous analgesia in horses without adverse cardiovascular and respiratory effects.