There has been a great increase in interest in veterinary acupuncture recently, both by the public and the veterinary medical
community. With this increased awareness, there has been an increase in research and thus a better understanding of the its'
physiologic basis and its clinical applications.
Scientific basis
Acupuncture (AP) may be defined as the stimulation of specific predetermined points on the body to achieve a therapeutic or
homeostatic effect. Acupuncture points are areas on the skin of decreased electrical resistance or increased electrical conductivity
Acupuncture points correspond to four known neural structures. Type I acupoints which makeup 67% of all acupoints, are considered
motor points. The motor point is the point in a muscle which when electrical stimulation is applied, will produce a maximal
contraction with minimal intensity of stimulation . Motor points are located near the point where the nerve enters the muscle.
Type II points are located on the superficial nerves in the sagittal plane on the midline dorsally and ventrally. Type III
acupoints are located at high density foci of superficial nerves and nerve plexi. For instance acupoint GB-34 is located at
the point where the common peroneal nerve divides into the deep and superficial branches. Type IV acupoints are located at
the muscle tendon junctions where the golgi tendon organ is located . Recently, histologic studies have revealed that small
microtubules consisting of free nerve endings, arterioles and venules penetrate through the fascia at acupuncture points.
Based on this histologic evidence they have also been called neurovascular nodes .
Acupuncture has many varied physiologic effects on all systems throughout the body . No one mechanism can explain all the
physiologic effects observed. The traditional chinese medical theories have explained these effects for four thousands years
based upon empirical observations and descriptions of naturally occurring phenomena. The traditional chinese medical theories
include: the five element theory and the theory of eight principles. Scientific research has been able to document many of
these effects. The western medical theories include the gate and multiple gate theories, autonomic theories, humeral mechanisms
as well as the bioelectric theories. The neural non-opiate or gate theory attempts to explain the analgesic effects of acupuncture.
It involves the interaction of inhibitory interneurons on pain transmitting neurons. Recent reviews of the latest research
on the neurophysiologic effects of acupuncture are available.
The neural opiate theory is based on evidence that acupuncture stimulates the release of endogenous opiates, endorphins and
encephalins. This mechanism acts at several levels in the central nervous system to inhibit pain perception in higher centers
and to inhibit pain transmission from the spinal cord via descending inhibition. The hormonal opiate theory involves the interaction
of neurons with the subsequent release of humoral factors from the hypothalamic-pituitary axis. Acupuncture facilitates the
function of the neuroendocrine system and has been found to have effects on ovarian, testicular, thyroid, parathyroid and
pancreatic function . Through its effects on the neuroendocrine system and its homeostatic regulatory functions it has been
found to effect blood pressure, pulse, respiration, gastrointestinal motility, hormone secretion, leukocyte production and
accelerate the healing process .
Many of our somatovisceral reflexes may be explained through the autonomic theories of acupuncture. Cutaneous needle stimulation
is transmitted to the internal viscera through the somatovisceral neuronal synapses in Laminae I & V of the spinal cord.
Essentially, acupuncture stimulates various sensory receptors (pain, thermal, pressure, touch) which stimulates sensory afferent
nerves which transmit the signal through the central nervous system to the hypothalamic-pituitary system. Various neurotransmitters
and neurohormones are then released and have their subsequent effects throughout the body. A detailed description of the physiologic
basis of acupuncture is reviewed by Steiss .
