Pain is defined as “a feeling of distress, suffering, or agony caused by stimulation of specialized nerve endings.” The scientific term for the perception of pain is “nociception,” with noci the Latin for “harm or injury.”

Pain and its control are one of the largest topics in medicine. A quick literature search on only one database going back to 1986 yields 58,700 articles pertaining to some aspect of pain (99 of which related specifically to pain in horses). Over the last century, the effort to control pain and suffering in people has been great, but it has only been in the last two decades that a similar effort has been directed toward our animal companions.

In 1987, an entire issue of the Journal of the American Veterinary Medical Association was devoted to animal pain by publishing the Colloquium on Recognition and Alleviation of Animal Pain and Distress. The issue included 40 articles by 32 authors on 23 topics related to the understanding of pain and its alleviation.

In an extremely simplified explanation, pain is first identified by special receptors at nerve endings. Once the signal, be it a sharp nail in the foot or a gas pocket in the colon, is detected by the receptor, the message is sent via nerves to the spinal cord. The spinal cord functions as a relay switch, where signals are potentially modified and sent up the spinal system to the brain. It is in the brain that the pain signals are processed, perceived, and the agony begins. This is oversimplified, but gives enough foundation for us to later discuss mechanisms for “blocking” pain at the receptor, in the spinal cord, and in the brain