Effects of nitric oxide inhibition on thermoregulation during exercise in the horse.

The research article explores the role of Nitric Oxide (NO) in thermoregulation (body temperature control) in horses during exercise. Particularly, how inhibiting NO production impacts sweating rate and body temperatures.

Research Methodology

• The study involved five thoroughbred horses which were made to exercise on a high-speed treadmill at varying intensity levels. Variables measured include the horse’s sweating rate and body temperatures (core, rectal, and skin).
• An exercise routine, called a standard exercise test (SET), was set up. It comprised of three canters (runs at a moderate pace), punctuated by periods of walking and trotting. Each horse was made to perform this exercise routine twice in a random sequence.
• After the first canter in the test SET, a compound known as N omega-nitro-L-arginine methyl ester (L-NAME), which inhibits NO synthase (NOS), was infused into the horse’s bloodstream. This action inhibits the production of NO.
• After the second canter, L-Arginine, a component necessary for the production of NO, was injected into the horse, both under normal circumstances (control) and after NO production had been inhibited (test).

Findings

• The findings showed that L-NAME significantly reduced the horse’s sweating rate, measured on the neck and rump, during the second canter. Simultaneously, it substantially increased the core temperature of the horses.
• In the third canter, the sweating rate had risen after injecting L-arginine during the test routine, although it did not return to levels recorded at similar times during the control routine.
• Despite the injection of L-arginine, the horse’s core, rectal, and skin temperatures continued to rise and were remarkably higher than control levels.

Conclusions

• The results from this study substantiate that blocking the production of nitric oxide decreases the sweating rate in horses during physical exercises. This inhibition thereby causes an increase in their body temperatures.
• This research provides valuable insights into the mechanisms of thermoregulation in thoroughbred horses which can be beneficial in areas such as sports physiology and veterinary medicine.