sábado, 22 de dezembro de 2007

Neurobiological Acupuncture

The effects of Acupuncture are explained by
physiological principles and mechanisms.
Wall P.D., Melzack R.1

Contemporary Medical Acupuncture is a therapeutic method based on technics that provide access the nervous system by means of peripheral neural stimulation and neuromodulation, which produce local, segmental and central responses, promoting a readjustment of neural, cerebral, hormonal, visceral, and immune functions. Stimulation has several targets, including receptors and pathways of different sensory modes related to proprioception and to tactile and temperature senses, motor innervation of muscles, and the main one, the neural net related to pain modulation.

The therapeutic process of Acupuncture promotes analgesia, normalisation of regulation and control of organic functions, immunity modulation, endocrine, autonomic and mental functions, and activation of regenerative processes.

Acupuncture yields biological effects of varied natures which are developed from stimulus applied at diverse structures and different systems subjacent to the acupoints. The signs introduced in these points, privileged sites of access to nervous and circulatory networks, produce changes which are translated into peculiar forms to each type of structure and modes of stimulus.

The nature, the shape, and the function of the majority of acupoints, structured channels which directly conduct to a complex vasculonervous, or which predominately involve the subjacent fascia, explain the scope of their therapeutic actions.

The stimuli applied at those points, which operate as transducers of entrance and exit of information, affect the various structures that share the space of these peripheral "doors" of organism-environment communication. Arteries, veins, lymphatic vessels, nerves of various types, all these elements are sensitive and responsive to slightest differences in their micro-environment.

In the neural segment, the nociceptive system fibres have a highlighted role, but they are not the only ones to be affected by Acupuncture stimulus. The stimulus also puts into action, and sometimes in a decisive way - because of the therapeutic importance of the obtention of the sensation described by the ancient Chinese as Deqi -, the myelinated non-nociceptive fibres, including those related to proprioception, the mechanoceptors, as well as the branches of the motor nerves.

Each type of stimulated structure generates specific responses, and there is also a specificity of action of the different modes of stimulus. These modes include simple needling, manipulations, electric stimulation of diverse modes (wave shape, duration, current intensity and frequency) which determine specific reactions that have been identified and standardised.

The consequences of stimulus on the other structures present in the site of stimulation - blood and lymphatic vessels, and musculo-skeletal structures, including fascias, tendons, aponeuroses and muscles, are still not completely explored. On the other hand, the relationship between these structures and other elements with which they communicate is a hypothesis coherent with the present data of physiology.

The role of the secretion and release of endhotelins originated from vessels walls, and the regional changes promoted by the action on muscular and fascial chains are explicit cases of the contribution of those structures in the treatment of referred pain due to hyperactivity of myofascial trigger points. The connection between acupoints and these peripheral structures with centres of the nervous system which integrate, process, update and generate systemic adaptive organic responses are much more important than we could have predicted 40 years ago.

Memories, stable configurations of neuronal circuitry, and patterns of communication between structures of the nervous system may be modified by the method which, activating a neuronal activity modulator system, exerts effects upon diverse neuro-hormones and neurotransmitters2. These facts have been extensively demonstrated, which provides solid bases for Acupuncture applications on emotional and affective disorders (case of depression), as well as on neurosomatic3 (or psycosomatic) and endocrine disorders.

Acupuncture exerts a physiological re-learning effect4,5, both because it modifies patterns of neuronal connectivity through the activation of peripheral devices of informational entrance which function as commands in an interface with decision centres, and also because it modulates neurotransmitters (like dynorphin) which are essential for long-term potentiation (LTP), basis of the changes involved with memory.

Impulses mainly originated in the limbic system, which integrates high level structures like the cerebral cortex with lowest ones, up to the peripheral terminations, affect all functions of regulation and control exerted by the central nervous system. It has been also suggested that the repeated activation of physiological systems of pain inhibition would train the organism to continue with this activity, maintaining pain relief for a long time, in a similar way to the training methods of the altered autonomic functions6.

1 . MELZACK R., WALL P.D., Textbook of Pain. 3ed., Churchill Livingstone, UK, 1994

2. MAYER D.J., Biological mechanisms of acupuncture. Prog Brain Res, 122: 457-77, 2000

3 . YUNUS M.B. Towards a model of pathopysiology of fibromyalgia: aberrant central pain mechanism with peripheral modulation. J Rheumatol, 19:846-850, 1992

4. BENSOUSSAN A. Does Acupuncture therapy resemble a process of physiological learning? Am J Acupun 22(2):137-44, 1994

5. LEE T.N. Academy of Pain Research, San Francisco, CA, Thalamic Neuron Theory: theoretical basis for the role played by the central nervous system (CNS) in the causes and cures of all diseases. Med-Hypotheses, 43(5):285-302, Nov 1994

6 . KLIDE A.M. An hypothesis for the prolonged effect of Acupuncture. Acupun & Eletrotherap Res Intl Journal 14:141-7, 1989

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