* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Mechanism of relation among heart meridian, referred cardiac pain
Survey
Document related concepts
Neural coding wikipedia , lookup
Electromyography wikipedia , lookup
Neural engineering wikipedia , lookup
Central pattern generator wikipedia , lookup
Development of the nervous system wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Neuroanatomy wikipedia , lookup
Synaptic gating wikipedia , lookup
Transcranial direct-current stimulation wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Optogenetics wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Neuroregeneration wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Evoked potential wikipedia , lookup
Transcript
Vol. 45 No. 5 SCIENCE IN CHINA (Series C) October 2002 Mechanism of relation among heart meridian, referred cardiac pain and heart RONG Peijing () & ZHU Bing ( ) Institute of Acupuncture-Moxibustion, CATCM, Beijing 100700, China Correspondence should be addressed to Zhu Bing (email: [email protected]) Received March 27, 2001 Abstract It has been demonstrated that an important clinical phenomenon often associated with visceral diseases is the referred pain to somatic structures, especially to the body area of homo-segmental innervation. It is interesting that the somatic foci of cardiac referred pain were often and mainly distributed along the heart meridian (HM), whereas the acupoints of HM have been applied to treat cardiac disease since ancient times. The purpose of this study was to investigate the neural relationship between the cardiac referred pain and the heart meridian. Fluorescent triple-labeling was injected into the pericardium, some acupoints of HM and lung meridian (LM, for control). The responses of the left cardiac sympathetic nerve and of the EMG in left HM and LM were electrophysiologically studied, when the electrical stimuli were applied to the acupoints of left HM and to the left cardiac sympathetic nerve. More double-labeled neurons in HM-heart, not in LM-heart, were observed in the ipsilateral dorsal root ganglia of the spinal segments C8-T3. Electric stimulation of the acupoints of left HM was able to elicit more responses of left cardiac sympathetic nerve than that of the LM-acupoints. Electric stimulation of the left cardiac sympathetic nerve resulted in stronger activities of EMG-response in the acupoints of left HM than in LM-acupoints. We conclude that double-labeling study has provided direct evidence for the existence of dichotomizing afferent fibers that supply both the pericardium and HM. Electrophysiological results show that HM is more closely related functionally to heart. These findings provide a possible morphological and physiological explanation for the referred cardiac pain and HM-heart interrelation. Keywords: dichotomization of DRG, heart, heart meridian, somato-visceral connection. Chinese ancient physicians and philosophers put forward the meridian doctrine of the traditional Chinese medicine, based on extensive clinical phenomena and therapeutic regularity. It is composed of 14 lines distributed in limbs and trunk. The relationship between meridians (soma) and zang-fu organs (viscera) is a key content of the meridian doctrine, which comprises the morpho-functional unit of somatic-visceral connections. The heart meridian (HM), one of the 14 meridians, is distributed along the medial part of the hand and brachium from first finger to the axilla. All the nine acupoints in HM can be used for treating coronary heart disease. Surprisingly, the somatic foci of referred cardiac pain are identical with the course of HM. We suggest that they have common biological bases. From the physiological viewpoint, one basis for convergence of visceral and somatic sensory information onto central neurons may be by way of the shared primary afferent fibers, and another basis of viscero-somatic convergence would be at the level of neurons in the central nervous sys- No. 5 HEART MERIDIAN & REFERRED CARDIAC PAIN 539 tem that are activated independently by visceral and somatic primary afferent fibers[1]. The latter mechanism would be most consistent with the “convergence-projection theory” of referred pain. Visceral pain is usually referred to a somatic area innervated by the homo-segments of spinal cord that receive the input from the originating viscus[2]. The connection between meridians and zangfu organs is also the basis of convergence of visceral and somatic afferent onto central neurons in the same spinal cord segments. Meridian-zangfu and somato-visceral connections might be the common realization in different times and in different scientific background. In the present study, we investigated the morphological and neurophysiological mechanisms of referred cardiac pain, heart and meridian-heart interrelation. A preliminary report of this work has appeared in an abstract form[3]. 1 Methods Experiments were performed on Sprague-Dawley rats weighing 200300 g anesthetized with urethane. Fluorescent dyes (Sigma), Bisbenzimide (Bb), Propidium Iodide (PI) and Fast Blue (FB) were composed in a saturated solution. In the morphological experiments, following anesthetization a longitudinal incision, about 3 cm in length, was made in the rostral portion of the ventral abdominal wall exposing the central tendon of the diaphragm. The position of the pericardial sac was located by identifying the base of the heart, which could be visualized through this thin central tendon. The pericardial sac was injected transdiaphragmatically with 15 µL of Bb and the site was then sealed with paraffin wax, which set as the needle was withdrawn to prevent leakage of the dye from the injection site. The incision was sutured and local antibiotics were used routinely. PI and FB were respectively microinjected into three HM acupoints (HT 1-3) on the medial side of the left brachium and three lung meridian (LM, for control) acupoints (LU 1, 3, 4) on the lateral side of the left brachium (each acupoint for 5 µL, about 24 mm in depth). It was noted that the points injected both in HM and LM should be located in the identical height anatomically. The injection sites were sealed with paraffin wax as the needle was withdrawn and the animal again allowed recovering. After an appropriate survival of 24 h, the rat was anesthetized and perfused transcardially with 4% sodium citrated saline until the perfusate was clear, which was followed by 4% paraformaldehyde in phosphate buffer (0.1 mol/L, pH 7.4). The left dorsal root ganglia (DRG) of the spinal segments cervical 6 (C6) to thoracic 4 (T4) were removed and immersed in a 4 solution of 15% sucrose in phosphate buffer. Sections (30 µm) were made by a cryostat at −20. The sections were then viewed using a Nikon-E600 microscope with a fluorescence vertical illuminator producing ultraviolet light of 365 nm excitation wavelength. Photomicrographs were made utilizing the same microscope. In the electrophysiological experiments, following surgery (tracheotomy) under anesthetics of 10% urethane (1 g/kg, ip), the animals were artificially ventilated through a tracheal cannula; the rate and volume of ventilation were adjusted to maintain a normal acid:base equilibrium as assessed with a capnometer. Heart rate was monitored continuously and core temperature was 540 SCIENCE IN CHINA (Series C) Vol. 45 maintained at 37 ± 1.0 by means of a homeothermic blanket system. Following anesthetization a longitudinal incision, about 2 cm in length, was made in the anterior cervical wall for exposing and isolating the left cardiac branch of sympathetic post-ganglionic fibers for stimulating or recording with a bipolar electrode. For electric stimulation and recording electromyography (EMG) responses of acupoints, a pair of noninsulated needle electrodes were inserted s.c. in HT3 and HT 7 acupoints, about 35 mm in depthon the medial side of the left brachium, and another pair of electrodes were inserted in LU5 and LU9 acupoints on the lateral side of the left brachium. The electric stimulus consisted of a volley of 25 rectangular pulses of 0.1 ms duration and was delivered every 30 s from a constant current stimulator. The stimulus intensity was initially adjusted to 1 mA and gradually increased to 10 mA. Such stimulation procedure might evoke stable cardiac sympathetic nerve and EMG responses. The cardiac sympathetic nerve responses and the EMG responses were fed to a storage oscilloscope to allow monitoring the experiments, and to a computerized system (Power-Lab system) for on-line digitization of data. The individual responses were plotted either against time to allow the study of their temporal evolution or against stimulus strength to build recruitment curves. For each sequence, numerical data concerning the effects of electro-acupuncture stimuli and cardiac sympathetic nerve stimuli were expressed as spike numbers. Global mean results were performed analysis of variance and were always presented as means ± SE. Paired t test and linear regression analysis were used for studying the significance of variations; a P value below was considered being significant. 2 Results Neurons labeled with fluorescent dyes were observed in the left DRG (C6-T4) of 11 rats and were mainly moderate (1530 µm) and small (<15 µm) cells. The fluorescence characteristics of the different tracers briefly described that, when the preparations were viewed under light of 365 nm wavelength, Bb containing neurons possessed a blue-green fluorescing nucleus while the cytoplasm was unstained or fluoresced only slightly; PI and Fb stained the cytoplasm orange-red and blue, respectively. Single-labeled neurons in HM and LM injection were 31.94% and 26.40%, and restricted mainly to C6-T1 and C6-8 segments, respectively; the neurons labeled following heart injection were 26.83% and the majority of single-labeled neurons was mainly restricted to segments T1-2 in the range of C6-T4 distributions. Fig. 1 shows the mean numbers of double-labeled neurons within the C6- T4 ganglia of 11 rats in 3 groups. HM-heart and LM-heart injection double-labeled neurons were 6.81% and 3.97% and mainly in C8-T3 and C7-8 segments, respectively; HM-heart double-labeled neurons were much more in comparison with the control LM-heart injection (P < 0.05). Only a few double-labeled neurons were observed in HM-LM injection (2.77%) and triple-labeled cells in HM-LM-heart injection were 1.28%. The distinction of Fb and Bb double-labeled neurons (HM-heart injection) is shown in plate I-3, in which the blue-green fluorescing nucleus and light-blue fluorescing cytoplasm can be clearly viewed; in plate I-4, the Fb and PI double-labeled neuron (LM-heart injection) of fluorescing the blue-green nucleus and orange-red No. 5 HEART MERIDIAN & REFERRED CARDIAC PAIN 541 cytoplasm can be distinguished. Plate I-1 is PI labeled neurons injected into the LM acupoint and plate I-2 is Bb labeled neurons injected in heart. 2.1 Left sympathetic responses induced by ipsilateral HM and LM acupoints stimuli 2.1.1 General characteristics of the sympathetic activities. In the majority of condition, the cardiac sympathetic nerve did not present spontaneous activity at the beginning of the testing sequences and a proportion developed residual activity; this activity consisted of irregular discharges of low magnitude. The cardiac sympathetic nerve responded to electric stimulation applied percutaneously to ipsilateral HM acupoints and two reflex components could be evoked in supramaximal electrical stimulation. Early and late reflex potentials had a latency about 20ü40 and 100ü Fig. 1. Distributions of double-labeled neurons in every dorsal root ganglia. , HM-heart; , LM-heart; , HM-LM. 150 ms, respectively. In the viewpoint of Sato, these responses were induced by the afferent myelinated (A) fibers and unmyelinated (C) fibers activations[4]. 2.1.2 Different thresholds of cardiac sympathetic nerve responses to stimulation applied to HM and LM acupoints. The cardiac sympathetic nerve gave the responses to electroacupuncture applied to ipsilateral HM acupoints with a mean threshold of (2.92 ± 0.38) mA; while same responses were elicited with a mean threshold of (4.92 ± 0.54) mA in LM acupoints stimulation, and the difference was highly significant (P < 0.05, n = 18). Fig. 2. Stimulations in HM-(left) and LM-(right) acupoints elicited ipsilateral cardiac sympathetic nerve responses. Stimulation of HM acupoints elicited larger sympathetic nerve responses in 2- to 8-mA range than that of LM acupoints. 2.1.3 Different magnitudes of cardiac sympathetic nerve responses to stimulation applied to HM and LM acupoints. All of the cardiac sympathetic nerve responses were elicited by HM and LM acupoints stimuli. This is illustrated by an individual example in fig. 2. It can be seen that the magnitudes of the responses of the cardiac sympathetic nerve were directly related to the stimulation applied to HM and LM acupoints at 28 mA. These findings are corroborated by the cumulative results presented in table 1, showing that both HM and LM acupoint stimulations monotonically increased the cardiac sympathetic nerve discharges in response to the application of electrical stimuli at 2 542 SCIENCE IN CHINA (Series C) Vol. 45 8 mA. 4-mA HM acupoint stimulation induced 11.62 ± 2.30 spikes in the sympathetic nerve, while the same stimulation of LM acupoints only produced 7.15±2.07 spikes. It is interesting to note that stimulation of HM acupoints elicited larger sympathetic nerve responses in 2- to 8-mA range than that of LM acupoints, and the difference was highly significant (P 0.050.02, n = 13). Table 1 Comparison of cardiac sympathetic nerve responses induced by stimulations in ipsilateral HM- and LM-acupoints HM-acupoints LM-acupoints 2.2 2 mA 4.231.49 1.540.87 4 mA 11.622.30 7.152.07 6 mA 18.623.23 12.082.51 8 mA 20.852.99 14.072.61 Left cardiac sympathetic nerve stimuli induced acupoints EMG responses in HM and LM 2.2.1 General characteristics of the EMG activities. When the needle electrode was inserted into the muscle, it evoked violent and irregular discharges of action potentials, only with a brief lasting of about 500 m and small amplitude. Electric stimulation of the cardiac sympathetic nerve elicited an EMG reflex multiphasic response in the ipsi-lateral HM and LM acupoints with 20 80 ms latencies for duration of 100200 ms; while these responses occasionally maintained 1 s duration in the condition of supra-maximal stimulation. 2.2.2 Different thresholds of EMG reflex responses of HM and LM acupoints induced by stimulation of cardiac sympathetic nerve. The left cardiac sympathetic nerve stimulation elicited EMG reflex response in the ipsilateral HM acupoints with a mean threshold of (1.75 ± 0.22) mA, while same responses elicited in LM acupoints required the stimulation with a mean threshold of (3.25 ± 0.41) mA. This difference was highly significant (P < 0.02, n = 12). 2.2.3 Different magnitudes of EMG reflex responses both at HM and LM acupoints elicited by ipsilateral cardiac sympathetic nerve stimulation. Electric stimulation of the cardiac sympathetic nerve elicited EMG reflex responses both at HM and LM acupoints in simultaneous application of a Double-Amplifier-Power-Lab system. The magnitudes of the responses of EMG were directly related to the stimulation applied to cardiac sympathetic nerve in 26 mA range, Fig. 3. Left cardiac sympathetic nerve stimulations in different strength induced EMG responses at both HM- and LM-acupoints. Cardiac sympathetic nerve stimulations elicited larger EMG responses at HM acupoints in 26 mA range. and the responses increased as stimulus strength increased. These findings are corroborated by the cumulative results presented in fig. 3, showing that the cardiac sympathetic nerve stimulations monotonically increased EMG discharges in response to the application of electrical stimuli in 26 mA range. 4-mA sympathetic nerve stimulation induced 11.17 ± No. 5 HEART MERIDIAN & REFERRED CARDIAC PAIN 543 1.96 action potentials at HM acupoints, while same stimulation produced only 4.67 ± 1.26 action potentials at LM acupoints. It is interesting to note that the cardiac sympathetic nerve stimulations elicited larger EMG responses at HM acupoints in 26 mA range than those at LM acupoints. This difference was highly significant (P 0.010.05, n = 12). 3 Discussion Single-, double- and triple-labeled neurons were observed in C6-T4 DRG following injection of fluorescent tracers into the pericardium and left medial (heart meridian) or lateral (lung meridian) brachium. Our results clearly indicate that more dichotomizing fibers that supply both the pericardium and the medial brachium exist and a closer relation between heart meridian and heart is observed. Dichotomizing afferents fibers have been proposed as a possible explanation for referred pain [1]. Cardiac pain is frequently referred to the medial but not the lateral aspect of the left brachium, and the referred region is identical with the route of the heart meridian, which suggests the existence of a similar mechanism between heart meridian and cardiac activity. A number of different mechanisms have been suggested in order to explain the somatic localization of the sensory experience evoked from viscera. All these models take into account the clinical observation that visceral pain is usually referred to a somatic area innervated by the same spinal segments that receive the input from the originating viscus[2]. Therefore, all the neurophysiological interpretation of visceral pain is based on viscero-somatic integration, that is, the convergence of inputs from viscera and from somatic structures onto sensory neurons whose activation leads to the experience of somatic pain [2]. The simplest form of viscero-somatic convergence occurs in primary afferent fibers with multiple peripheral branches that innervate sensory receptors in skin, muscle and viscera. Electrophysiological and double-labeling studies have provided direct evidence for the existence of dichotomizing peripheral afferents that supply both visceral and somatic structures. Bahr et al.[5] have reported that such dichotomizing primary afferent neurons constitute 18% of the total number of cells in the DRG of the cat. But in the rat, Dawson et al.[6] demonstrated that, by means of intraneural injection of tracers, the frequency of pre-spinal somato-visceral convergence averaged 2%. Alles and Dom[7] have observed dichotomizing afferent fibers in ipsi-lateral DRG neurons of spinal cord segments C8, T1 and T2, when two tracers were respectively injected into the pericardium and the brachium. This finding provides a possible morphological explanation for referred cardiac pain. We would therefore like to propose the dichotomizing pericardial and heart meridian in the medial brachium afferent as an alternative anatomical base for explanation of both the referred cardiac pain and heart meridian-heart. Acupuncture treatment of coronary heart disease is a common therapy, and one of its main actions is to relieve angina pectoris. Acupuncture or somatic physical and chemical stimulations are able to produce satisfactory analgesia, especially in the condition of these stimuli application at homo-segmental level with relative visceral organ. Selze and Spenser[8] reported that the somatic stimulations could strongly inhibit afferent activities of viscera. It produced an inhibition of transmission by depolarization of the afferent terminals and is involved in pre-synaptic 544 SCIENCE IN CHINA (Series C) inhibition. Several groups[9 ü11] Vol. 45 have clearly observed that the visceral afferent activities in some neurons of dorsal horn in the spinal cord can be strongly depressed by homo-segmental somatic stimuli. Our pervious results have already confirmed that the nociceptive reflex and painful sensation were inhibited by the electroacupuncture applied at the homotopic acupoint in the strength less than pain threshold[12]. In general viewpoint, the bases of meridians-viscera connection are involved in somato-sympathetic reflex, and acupuncture at HM-acupoints is able to treat some cardiac diseases. We observed that, in the present study, electric stimulation of left HM-acupoints evoked greater reflex responses of the ipsi-lateral cardiac sympathetic nerve than the same stimulation applied to the LM-acupoints. Left cardiac sympathetic activity was especially able to strengthen the myocardial function and to produce the coronary vasodilatation in muscular vasoconstriction[13]. These reflex responses elicited by the stimulation applied to HM-acupoints are helpful to the treatment of coronary heart disease. Sato[14], on the basis of reviewing the majority data, has indicated that somatic afferent nerve stimulation can regulate various visceral functions by reflex responses and the effects of somatic afferent stimulation are dependent upon the particular organs and on the spinal afferent segments. These responses include both generalization (e.g. in cerebral cortical blood flow, heart rate, and adrenal medullary hormonal secretion and splenic immune function) and strong segmental organization. The responses of sympathetic and parasympathetic efferent nerves to the somatovisceral reflexes depend on the individual organ, the segmental site being stimulated and the nature or intensity of the stimulation. Somato-sympathetic reflexes are strongly segmental in the spinalized animal preparation. The result, that electric stimulation of the left cardiac sympathetic nerve resulted in strong activities of EMG-response in the acupoints of left HM than in the acupoints of left LM, indicates that somato-sympathetic reflexes have clearly the characteristic of segmental distribution[15]. The various studies[16 ü19] tend to suggest that the myotonic band appears along some meridians or along longitudinal muscles in the condition of visceral pathologies, which is in the homo-segmental innervation with the somatic structures. Acknowledgements This work was supported by the Climbing Program of Chinese Committee of Sciences and State Administration of Traditional Chinese Medicine. References 1. Cervero, F., Tattersall, J. E. H., Somatic and visceral sensory integration in the thoracic spinal cord, Prog. Brain Res., 1986, 2. Foreman, R. D., Blair, R. W., Ammons, W. S., Neural mechanisms of cardiac pain, Prog. Brain Res., 1986, 67: 227243. 3. 4. Rong, P. J., Zhu, B., Research on the mechanism of relation between cardiac referred pain and heart meridian, Chinese J. Neuroscience, 2001, 17(suppl.): 269. Sato, A., Sato, Y., Schmidt, R. F., Modulation of somatocardiac sympathetic reflexes mediated by opioid receptors at the 5. Bahr, R., Blumberg, H., Jänig, W., Do dichotomizing afferent fibres exists which supply visceral organs as well as somatic 67: 189205. spinal and brainstem level, Exp. Brain Res., 1995, 105: 16. structures? A contribution to the problem of referred pain, Neurosci. Lett., 1981, 24: 2528. No. 5 HEART MERIDIAN & REFERRED CARDIAC PAIN 545 6. Dawson, N. J., Schmid, H., Pierau, Fr. -K., Pre-spinal convergence between thoracic and visceral nerves of the rat, Neuro- 7. Alles, A., Dom, R. M., Peripheral sensory nerve fibers that dichotomize to supply the brachium and the pericardium in the 8. Selzer, M. E., Spenser, W. A., Convergence and reciprocal inhibition of visceral and cutaneous afferents in the spinal cord, 9. Pomeranz, B., Wall, P. D., Weber, W. V., Cord cells responding to fine myelinated afferents from viscera, muscle and skin, 10. Gokin, A. P., Kostyuk, P. G., Preobrazhensky, N. N., Neuronal mechanisms of interactions of high-threshold visceral and 11. Foreman, R. D., Hancock, M. B., Willis, W. D., Responses of spinothalamic tract cells in the thoracic spinal cord of the 12. Zhu, B., Xu, W. D., Acupuncture stimulation-induced analgesia: it involved in segmental and systemic controls, Fifth IBRO World Congress of Neuroscience, Jerusalem: JU Press, 1999, 45. 13. Wang, Z. D., Xu, Y. H., Physiology of Autonomic Nervous System (in Chinese), Beijing: Science Press, 1994, 154177. 14. Sato, A., Neural mechanisms of autonomic responses elicited by somatic sensory stimulation, Neurosci. Behav. Physiol., 15. Zhu, B., Scientific Foundations of Acupuncture-Moxibustion (in Chinese), Qingdao: Qingdao Publishing House, 1998, 16. Giamberardino, M. A., Vecchiet, L., Visceral pain, referred hyperalgesia and outcome: new concepts, Eur. J. Anaethesiol., 17. Morrison, J. F., Sato, A., Sato, Y. et al., The influence of afferent inputs from skin and viscera on the activity of the blad- 18. Tola, M. A., Gutierrez, J. M., Llamazares, O. et al., Muscular spasms associated with a reflex sympathetic dystrophy, Rev. 19. Grassi, C., Passatore, M., Spontaneous sympathetic command to skeletal muscles: functional implications, Func. Neurol., sci. Lett., 1992, 138: 149152. rat: a possible morphological explanation for referred pain? Brain Res., 1985, 342: 382385. Fed. Proc., 1967, 26: 433446. J. Physiol., 1968, 199: 511532. somatic afferent influences in spinal cord and medulla, J. Physiol. (Paris), 1977, 73: 319333. monkey to cutaneous and visceral inputs, Pain, 1981, 11: 149162. 1997, 21: 610621. 446450. 1995, 12(suppl. 10): 6166. der and skeletal muscle surrounding the urethra in the rat, Neurosci. Res., 1995, 23: 195205. Neurol., 1986, 134: 12781280. 1990, 5: 227232. 546 SCIENCE IN CHINA (Series C) RONG Peijing et al.: Heart meridian & referred cardiac pain Vol. 45 Plate I Photomicrograph of DRG double-labeled neurons. 1, PI single labeled neurons injected into the LM acupoint; 2, Bb single labeled cells injected in heart; 3, HM-heart Fb and Bb double-labeled neurons viewed the blue-green fluorescing nucleus and light-blue fluorescing cytoplasm; 4, LM-heart Fb and PI double-labeled neurons viewed the blue-green fluorescing nucleus and orange-red fluorescing cytoplasm.