In evidence-based integrative veterinary medicine, science and testing become the final arbiters of whether modalities are embraced or rejected. While approaches such as medical acupuncture pass this test with flying colors, others, such as surrogate-applied kinesiology and iridology, fail to leave the starting gate.
As the leading choice for neurologic recovery, acupuncture (somatic afferent nerve stimulation) wins again as the most studied and best understood of all complementary and alternative medical techniques.1–10
Neuroanatomically designed needling protocols address neurophysiologic dysfunction peripherally, autonomically and centrally. After a medical acupuncturist identifies the locus of the lesion, she selects stimulation methods shown to repair nerve tissue at the site of damage and facilitate communication throughout the neural network.
Points that target autonomic function promote homeostatic regulation and systemic recovery; their incorporation in acupuncture treatments draws from insights derived from translational research and evidence-based clinical trials.
Exposing the science behind acupuncture facilitates its integration into mainstream medicine and elevates the discussion from metaphors to meaning
ful mechanisms. In the case of neurologic injury, for example, information about how acupuncture affects neural regrowth is steadily mounting. Studies are revealing that a heady multitude of endogenous biological mediators—growth factors, neurotransmitters and cytokines—participate in a sophisticated and complex neurophysiologic dance in response to electroacupuncture.
Ongoing scientific inquiry has thus painted a far more intricate picture than those generated by early scientific explanations about endorphins and pre-scientific metaphors about Qi and blood stagnation.11
Recently, neurotrophins (NTs), a group of proteins that promote or induce the survival, development and function of neurons, have attracted the attention of researchers evaluating the mechanisms of neurorehabilitative acupuncture. NTs such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) account for the bulk of repair and plasticity changes exhibited by neural tissue following neurodegeneration or traumatic injury.12
NGF, the first NT named, supplies essential support for neuronal health in both the peripheral and central nervous systems. Large quantities of NGF reside in vital brain centers such as the hippocampus, cortex and pituitary gland; significant amounts appear in the basal ganglia, thalamus, spinal cord and retina. Beyond its neural repair attributes, NGF also affects the immunologic-hematopoietic system and neuroendocrine balance, implicating its role in body-wide communication consistent with its position as a psychoneuroimmunologic mediator molecule.
Like NGF, BDNF lives in the retina and other central nervous system tissues. Low BDNF activity causes developmental brain defects, dementia, depression and a host of other brain disorders. More newly recognized NTs such as NT-3 and NT4/5 influence the development and maintenance of the enteric nervous system and motor neuron activities, respectively.
Given the near widespread, versatile functions of NTs and the negative ramifications of their depletion, researchers are investigating whether exogenously supplied NGF would help individuals with central or peripheral neurodegeneration, Alzheimer’s disease, peripheral neuropathy and epithelial or vasculopathic abnormalities causing corneal, pressure, or diabetic ulcers.
In contrast, since NGF may be involved in neuropathic pain production and dysautonomia, blockade of NGF has been attempted in some cases. Adverse side effects arising from both approaches, however, have prompted focus to shift to treatment strategies aimed at endogenously modulating (i.e., normalizing) NGF concentrations with interventions such as acupuncture and related techniques.
This is where the safe, relatively non-invasive neuromodulatory capacity of medical acupuncture shines. Evidence is accruing that, in addition to affecting mechanoreceptors, neurotransmission, nitric oxide, inflammation and more, acupuncture evokes changes in NT concentration in the central, peripheral and autonomic nervous systems.
Interest in NTs among acupuncture physiologists began about six years ago when researchers identified a correlation between NGF changes and acupuncture in a rat model for polycystic ovary syndrome. PCOS is a mainly a human endocrine dysfunction worsened by heightened sympathetic tone.13 Through systematic study, links surfaced between NGF and the benefits of electroacupuncture for lowering sympathetic overdrive.
Investigators surmised that EA modulates autonomic nervous system activity at least in part by imparting a peripheral down-regulation of NGF levels in organs, peripheral nerves and the spinal cord, resulting in a long-lasting reduction in sympathetic tone. In addition, EA counteracts the onset of NGF-associated hyperalgesia following chronic NGF administration, improving the likelihood that patients suffering from neuropathic pain will tolerate exogenously-applied NGF in the clinical setting.14
In the central nervous system, low-frequency EA applied to a rat model of human retinitis pigmentosa led to a partial recovery of normal retinal morphology by regulating NGF and BDNF levels or their receptors in retinal cells. EA raised vascular-endothelial growth factor (VEGF) levels, a finding that paralleled improved vascularity in the retina.15
Indeed, neurotrophic proteins may account for producing a much wider array of the psychoneuroimmunologic effects associated with acupuncture than previously recognized. EA stimulation restored BDNF levels in the rat hippocampus after stress.16 High-frequency EA up-regulates BDNF in dopaminergic neurons of the ventral midbrain in a Parkinson’s disease model involving mice.17
Additional studies have explored the effect of EA-induced NT changes for neurologic recovery in conditions such as neuropathic pain, inflammation, spinal cord injury, spinal cord plasticity, and the survival and migration of transplanted stem cells in injured spinal cord.18
By co-administering NTs and EA, clinicians may find that patients recover from a host of neurologic injury and ailments faster and more fully with fewer side effects.
Narda Robinson, DVM, DO, Dipl. ABMA, FAAMA, oversees complementary veterinary education at Colorado State University.
This article first appeared in the August 2010 issue of Veterinary Practice News.
1. Sharifi D, Bakhtiari J, Sarhadi M, et al. Comparative use of electromyography in the evaluation of electroacupuncture and transcutaneous electrical neural stimulation (TENS) effect on regeneration of sciatic nerve in dog. Iranian Journal of Veterinary Surgery. 2007;2(3):14-23.
2. Dorsher PT and McIntosh PM. Acupuncture’s effects in treating the sequelae of acute and chronic spinal cord injuries: a review of allopathic and Traditional Chinese Medicine literature. eCAM. 2009; 1-8; doi:10.1093/ecam/nep010
9. Li W-J, Pan S-Q, Zeng Y-S, et al. Identification of acupuncture-specific proteins in the process of electro-acupuncture after spinal cord injury. Neurosci Res. 2010; doi:10.1016/j.neures.2010.04.012
15. Pagani L, Manni L, and Aloe L. Effects of electroacupuncture on retinal nerve growth factor and brain-derived neurotrophic factor expression in a rat model of retinitis pigmentosa. Brain Res. 2006;1092:198-206.
17. Liang XB, Liu XY, Li FQ, et al. Long-term high-frequency electro-acupuncture stimulation prevents neuronal degeneration and up-regulates BDNF mRNA in the substantia nigra and ventral tegmental area following medial forebrain bundle axotomy. Brain Res Mol Brain Res. 2002;108:51-59.