Comparison perception of singular transcranial magnetic stimuli by subjectively electrosensitive subjects and general population controls

Transcranial magnetic stimulation of the dorsolateral prefrontal cortex by single pulses of varying field intensities was used to measure thresholds of individual perception and motor response in three groups of subjects: subjectively electrosensitive people, general population controls with a high burden of complaints related to electromagnetic field (EMF) exposure in the literature (highest decile in complaint burden), and general population controls with a low burden of complaints (lowest decile in complaint burden). The major study endpoint was the ability of the subjects to differentiate between real magnetic stimulation and a sham condition. There were no significant differences between groups in the thresholds, neither of detecting the real magnetic stimulus nor in motor response. But the three groups differed significantly in differentiating between stimulation and sham condition, with the subjectively electrosensitive people having the lowest ability to differentiate and the control group with high level of EMF-related complaints having the best ability to differentiate. Differences between groups were mostly due to false alarm reactions in the sham condition reported by subjectively electrosensitives (SES). We found no objective correlate of the self perception of being "electrosensitive." Overall, our experiment does not support the hypothesis that subjectively electrosensitive patients suffer from a physiological hypersensitivity to EMFs or stimuli. Further research should focus on disposing factors explaining the unspecific sensory hyperresponsiveness of subjectively electrosensitive subjects.     

Human head exposure to a 37 Hz electromagnetic field: effects on blood pressure, somatosensory perception, and related parameters

Previous studies have shown that exposure to an electromagnetic field (EMF) of 37 Hz at a flux density of 80 microT peak enhances nociceptive sensitivity in mice. Here we examined the effects on pain sensitivity and some indexes of cardiovascular regulation mechanisms in humans by measuring electrical cutaneous thresholds, arterial blood pressure, heart rate and its variability, and stress hormones. Pain and tolerance thresholds remained unchanged after sham exposure but significantly decreased after electromagnetic exposure. Systolic blood pressure was significantly higher during electromagnetic exposure and heart rate significantly decreased, both during sham and electromagnetic exposure, while the high frequency (150-400 mHz) component of heart rate variability, which is an index of parasympathetic activity, increased as expected during sham exposure but remained unchanged during electromagnetic exposure. Cortisol significantly decreased during sham exposure only. These results show that exposure to an EMF of 37 Hz also alters pain sensitivity in humans and suggest that these effects may be associated with abnormalities in cardiovascular regulation.     

Effects of Acupuncture on Sensory Perception: A Systematic Review and Meta-Analysis

Background

The effect of acupuncture on sensory perception has never been systematically reviewed; although, studies on acupuncture mechanisms are frequently based on the idea that changes in sensory thresholds reflect its effect on the nervous system.

Methods

Pubmed, EMBASE and Scopus were screened for studies investigating the effect of acupuncture on thermal or mechanical detection or pain thresholds in humans published in English or German. A meta-analysis of high quality studies was performed.

Results

Out of 3007 identified articles 85 were included. Sixty five studies showed that acupuncture affects at least one sensory threshold. Most studies assessed the pressure pain threshold of which 80% reported an increase after acupuncture. Significant short- and long-term effects on the pressure pain threshold in pain patients were revealed by two meta-analyses including four and two high quality studies, respectively. In over 60% of studies, acupuncture reduced sensitivity to noxious thermal stimuli, but measuring methods might influence results. Few but consistent data indicate that acupuncture reduces pin-prick like pain but not mechanical detection. Results on thermal detection are heterogeneous. Sensory threshold changes were equally frequent reported after manual acupuncture as after electroacupuncture. Among 48 sham-controlled studies, 25 showed stronger effects on sensory thresholds through verum than through sham acupuncture, but in 9 studies significant threshold changes were also observed after sham acupuncture. Overall, there is a lack of high quality acupuncture studies applying comprehensive assessments of sensory perception.

Conclusions

Our findings indicate that acupuncture affects sensory perception. Results are most compelling for the pressure pain threshold, especially in pain conditions associated with tenderness. Sham acupuncture can also cause such effects. Future studies should incorporate comprehensive, standardized assessments of sensory profiles in order to fully characterize its effect on sensory perception and to explore the predictive value of sensory profiles for the effectiveness of acupuncture.     

Threshold of pain in chronic magnetic field- (50 Hz, 17.9 microT) exposed rats: effect of sucrose ingestion

Both magnetic field (MF) exposure and sucrose ingestion produce opioid mediated analgesia, independently. This article addresses the query whether or not sucrose ingestion potentiates the analgesia of MF exposure. The pain threshold, as reflected by withdrawal of tail (thresholds of tail flick, TF), vocalization during stimulus (VD), and vocalization after stimulus (VA) were determined in 7 sessions at 0, 5, 10, 15, 30, 45, and 60 min, respectively (control rats). After an interval of 24 h the rats were provided with sucrose solution and were allowed to ingest it for 10 min. The pain thresholds were determined (Control sucrose-fed rats). The rats then received exposure to magnetic field (50 Hz, 17.9 microT) for 7 d (8 h/d) (MF-exposed rats) and the effect of sucrose ingestion was repeated (MF-Sucrose-fed rats). The basal threshold of pain did not vary in between the control and MF-exposed rats. Pain threshold during sessions II-VII did not vary in control rats but it increased in MF rats. Moreover, the pain thresholds were elevated in MF rats as compared to control rats. Sucrose-ingestion elevated the threshold of TF in controls but not in MF-exposed rats; while the thresholds of VA and VD were elevated more in control than MF rats. The results suggest that the MF exposure (50 Hz, 17.9 microT, 8 h/d) for 7 d did not affect the basal thresholds of pain, increased stress induced analgesia, and attenuated the sucrose ingestion-induced analgesia.     

Tolerance to morphine-induced analgesia in mice: Magnetic fields function as environmental specific cues and reduce tolerance development

Mice receiving daily injection of morphine (10 mg/kg) developed tolerance to morphine-induced analgesia, such that after 5–7 days of treatment their thermal response (paw licking) latencies in the hot plate test were indistinguishable from those of control animals. Exposure to a rotating magnetic field for thirty minutes before the daily morphine administrations significantly reduced the development of tolerance. These magnetic exposure also significantly increased over 7–10 days the basal nociceptive thresholds and paw licking response latencies of saline treated mice. Control and sham exposed mice that were fully tolerant to the analgesic effects of morphine failed to show any tolerance to morphine-induced analgesia when exposed to the magnetic stimuli prior to injection. Likewise, the partial tolerance to morphine shown by mice exposed to the rotating magnetic field pre-injection environmental cues was eliminated when control or sham pre-injection cues lacking the magnetic stimuli were provided. In all cases tolerance to morphine-induced analgesia was evident in the subsequent re-test with the original cues. These results indicate that magnetic field exposure can reduce the development of tolerance to the analgesic effects of morphine. They also show that magnetic stimuli function as significant environmental cues for the development of tolerance to morphine-induced analgesia. This suggests that magnetic stimuli affect both the associative (classical conditioning) and non-associative (physiological, pharmacological) mechanisms involved in the development of opiate tolerance.     

1．06μm激光致皮肤痛觉效应的研究

目的：研究1．06μm激光所致人手背皮肤的痛觉效应。方法：以输出波长为1．06μm的脉冲Nd：YAG激光照射人手背皮肤,记录每次刺激激光的能量以及受试者的反应。采用加权概率单位算法计算诱发痛觉概率为50％时对应的激光剂量ED50,即为痛觉阈值。改变光斑大小和脉冲宽度,测定三种不同刺激条件下的痛觉阈值,并探索温度对激光所致痛觉效应的影响。结果：当皮肤温度约为30℃,分别使用光斑直径1．20mm、脉冲宽度85μs,光斑直径1．20mm、脉冲宽度20ns和光斑直径2．56mm、脉冲宽度20ns的激光刺激时,痛觉阈值分别为394mJ／mm^2、36．4mJ／mm^2和8．92mJ／mm^2。在第一种刺激条件下,当皮肤温度为25℃时,剂量为383mJ／mm^2的激光诱发痛觉的概率为16．7％;当皮肤温度为39℃时,剂量为361mJ／mm^2的激光诱发痛觉的概率为56．7％。结论：1．06“m激光所致痛觉的阈值随脉冲宽度的减小、光斑面积的增大和皮肤表面温度的增加而减小。     

Otilonium bromide enhances sensory thresholds of volume and pressure in patients with irritable bowel syndrome.

Visceral hyperalgesia has been suggested to play a role in the development of symptoms presented by irritable bowel syndrome patients. Otilonium bromide was developed to block smooth muscle Ca release to control cramping pain of these patients. Aims: to determine whether otilonium bromide can influence sensory thresholds of patients suffering from irritable bowel syndrome. METHODS: 15 patients with Rome-II positive IBS were tested by Synectics Visceral Stimulator Barostat using rapid phasic distension (870 ml/min). The sensory threshold for first sensation, stool, pain and maximum tolerable volume and pressure were measured. All of the parameters were tested before and 1 week after the initiation of otilonium bromide (Spasmomen, Berlin Chemie, 3x40 mg) therapy. RESULTS: The perceptual thresholds for first sensation, stool, pain and maximum tolerable distention were, 8.8+/-1.7 Hgmm, 19.2+/-2.1 Hgmm, 26.3+/-2.8 Hgmm, 28.7+/-2.8 Hgmm for pressure, 90+/-21 ml, 145+/-28 ml, 208+/-25 ml, 213+/-28 ml for volume, before treatment, respectively. Otilonium bromide treatment did not influence the thresholds for first sensation and stool, 7.4+/-1.4 Hgmm, 20.7+/-4.6 Hgmm and 83+/-21 ml, 178+/-35.8 ml, respectively. The pressure threshold of pain was significantly higher 1 week after treatment (26.3+/-2.8 Hgmm vs. 29.1+/-5.5 Hgmm, P<0.05), but the volume threshold of this sensation remained unchanged (208+/-25 ml vs. 234+/-39 ml, not significant). The pressure (28.7+/-2.8 Hgmm vs. 38.1+/-3.4 Hgmm, P<0.05) and volume (213+/-28 ml vs. 278+/-27 ml, P<0.05) thresholds for maximum tolerable volume were increased by 7 days otilonium bromide treatment. CONCLUSION: These data suggest that otilonium bromide enhances sensory thresholds to recto-sigmoideal distention.     

苦参注射液联合普瑞巴林对脊神经结扎大鼠疼痛的影响

目的:探讨苦参注射液与普瑞巴林合用的镇痛效果,为临床用药提供实验依据。方法:通过结扎L5脊神经建立大鼠神经病理性疼痛模型。按照痛阈值将模型成功大鼠随机分为3组,分别为肌肉注射苦参注射液、口服普瑞巴林、苦参注射液和普瑞巴林联合用药。采用Von Frey纤维丝测定机械痛阈值,热板法测定热痛阈值,比较3组大鼠的机械痛阈值和热痛阈值的差异。结果:苦参注射液组大鼠机械痛镇痛效果第7天出现,热痛镇痛效果第21天出现,大鼠机械痛阈值和热痛阈值显著升高。口服普瑞巴林组大鼠机械痛阈值和热痛阈值在30分钟内显著升高,但机械痛阈值在给药第8天时下降到给药前水平,热痛阈值给药第5天时下降到给药前水平。联合使用苦参注射液和普瑞巴林,大鼠机械痛阈值和热痛阈值于给药后第1天显著升高,镇痛效果一直维持至实验结束(第28天)。结论:苦参注射液镇痛起效慢,不易产生耐受性。普瑞巴林镇痛起效快,但容易产生耐受。二者联合使用既可短时间内起到镇痛效果,并且不易产生耐受。     

Theoretical limits on the threshold for the response of long cells to weak extremely low frequency electric fields due to ionic and molecular flux rectification.

Understanding exposure thresholds for the response of biological systems to extremely low frequency (ELF) electric and magnetic fields is a fundamental problem of long-standing interest. We consider a two-state model for voltage-gated channels in the membrane of an isolated elongated cell (Lcell = 1 mm; rcell = 25 micron) and use a previously described process of ionic and molecular flux rectification to set lower bounds for a threshold exposure. A key assumption is that it is the ability of weak physical fields to alter biochemistry that is limiting, not the ability of a small number of molecules to alter biological systems. Moreover, molecular shot noise, not thermal voltage noise, is the basis of threshold estimates. Models with and without stochastic resonance are used, with a long exposure time, texp = 10(4) s. We also determined the dependence of the threshold on the basal transport rate. By considering both spherical and elongated cells, we find that the lowest bound for the threshold is Emin approximately 9 x 10(-3) V m-1 (9 x 10(-5) V cm-1). Using a conservative value for the loop radius rloop = 0.3 m for induced current, the corresponding lower bound in the human body for a magnetic field exposure is Bmin approximately 6 x 10(-4) T (6 G). Unless large, organized, and electrically amplifying multicellular systems such as the ampullae of Lorenzini of elasmobranch fish are involved, these results strongly suggest that the biophysical mechanism of voltage-gated macromolecules in the membranes of cells can be ruled out as a basis of possible effects of weak ELF electric and magnetic fields in humans.     

Skin potential and EMG changes induced by cutaneous electrical stimulation. II. Subjects with reflex sympathetic dystrophies.

In a group of patients suffering from reflex sympathetic dystrophies, the skin potential and EMG responses induced by electrical stimuli applied to the skin were recorded in the four limbs in order to study somato-sympathetic and somato-motor reflexes. In most patients, the amplitude, delay and shape of the cutaneous responses as well as the pattern of the EMG responses were different from those observed in normal subjects. In particular, it was possible to correlate the pattern of the cutaneous and muscular responses with the severity of the disease. The cutaneous sensory thresholds to electrical stimuli (tactile, tingling and pain threshold) showed different values in the dystrophic and in the contralateral limb. In all patients, a block of the sympathetic chain ipsilateral to the dystrophic limb was performed with local anesthetics. 1 h after the block, the cutaneous responses disappeared not only in the blocked limb but also in the contralateral limb. 48 h after the block, muscular and cutaneous responses as well as sensory thresholds showed a pattern similar to that observed in normal subjects. These findings show that the sympathetic block provides a resetting of the sensory thresholds and reflexes.     

Stimulus features relevant to the perception of sharpness and mechanically evoked cutaneous pain

Mechanical probes of various sizes and shapes were used to determine thresholds for the perception of pressure, sharpness, and pain on the human finger. As force increased, perception changed from dull pressure to sharp pressure to sharp pain. With the smallest probe (0.01 mm2), sharpness threshold was very close to pressure threshold. As probe size increased, sharpness and pain threshold expressed in terms of force) increased in proportion to probe circumference (not probe area), whereas pressure threshold increased relatively little. Pain and sharpness thresholds also increased as probe angle became obtuse. There was a statistically significant increase in both thresholds with a probe angle change of 15 degrees. Thus, both size and shape are necessary to describe a mechanical stimulus adequately, and pressure (force/area) is not a sufficient metric for pain studies. Thresholds varied at different skin sites on the finger. The dorsal surface had lower thresholds than the volar surface, but the difference between the two areas was not always statistically significant. The compliance of the skin (e.g., the amount of indentation produced by a given force) exhibited no relation to sharpness or pain threshold, whether considered within subjects at various skin sites, or across subjects at the same skin site. Comparison of the perceptual thresholds with the thresholds for nociceptors determined in electrophysiological studies indicates that the sensation of nonpainful sharpness is likely to be mediated by nociceptors. Furthermore, considerably more than threshold activation of nociceptors is necessary for normal pain perception.     

Extremely low frequency magnetic field exposure modulates the diurnal rhythm of the pain threshold in mice

The aim of this study was to determine whether exposure to extremely low frequency magnetic field (ELF-MF) affects the normal diurnal rhythm of the pain threshold in mice. Pain thresholds were evaluated in mice using the hot plate test. A significant increase of pain threshold during night was observed compared to that during day. This rhythm was attenuated by both constant exposure to light (LL) and constant exposure to darkness (DD) for 5 days. Under DD exposure, the diurnal rhythm in pain threshold was restored when mice were exposed to ELF-MF (60 Hz, 1.5 mT for 12 h daily, from 08:00 to 20:00 h) for 5 days. The diurnal rhythm was not reversed under dark with reversed ELF-MF cycle (exposure to 1.5 mT from 20:00 to 08:00 h, next day) for 5 days, although pain threshold in the ELF-MF exposed period of night was slightly decreased. The diurnal rhythm of melatonin analgesic effect related to pain threshold was also observed under DD by the exposure of ELF-MF for 5 days, but not for 5 nights. The present results suggest that ELF-MF may participate in the diurnal rhythm of pain threshold by acting on the system that is associated with environmental light-dark cycle.     

Tolerance responses to herbivory: implications for future management strategies in potato

Tolerance is a plant response to herbivory that allows plants to sustain defoliation without any fitness consequences. In agriculture, the maximum amount of defoliation that crops can experience without yield loss is defined as the damage threshold. Damage thresholds can be used to develop tolerance‐based management strategies, which would offer guidelines for farmers for when pest control should be enacted to minimise pesticide use while maintaining yield. Damage thresholds for many varieties of potatoes, Solanum tuberosum, have been documented, but not consolidated into a general framework. We aggregated data from published studies and quantified the effects of variety, maturity group, life stage and defoliation mechanisms on damage thresholds to inform a tolerance‐based management strategy for potato. Late maturing varieties did not have different damage thresholds than early maturing varieties. Damage thresholds were greater than 60% defoliation at emergence and post‐bloom and less than 40% defoliation pre‐bloom and during bloom. If the stems were damaged, emergence and post‐bloom damage thresholds were reduced from 60% defoliation without stem damage to 35% and 52% defoliation with stem damage. Likewise, the damage thresholds during bloom were reduced to 20% defoliation when stems were damaged. We propose using action thresholds based on defoliation as a baseline to develop a tolerance‐based management strategy for potatoes.     

Skin potential and EMG changes induced by cutaneous electrical stimulation. I. Normal man in arousing and non-arousing environment.

Skin potential and EMG responses induced in normal man by electrical stimuli applied to the skin were recorded in the four limbs in order to study somato-sympathetic and somato-motor reflexes. Different patterns of responses were observed in different conditions: alarm, habituation, sensitization and arousal. During alarm, sensitization and arousal, the responses were present in the four limbs; during habituation, the responses were only present in the stimulated and in the contralateral limb. Three sensory thresholds to cutaneous electrical stimulation were identified in habituated subjects: tactile, tingling and pain. Cutaneous and EMG responses appeared at tingling threshold. A relationship between skin potential level and skin potential response was observed.     

Systemic Inflammation Decreases Pain Threshold in Humans In Vivo

Background

Hyperalgesia is a well recognized hallmark of disease. Pro-inflammatory cytokines have been suggested to be mainly responsible, but human data are scarce. Changes in pain threshold during systemic inflammation evoked by human endotoxemia, were evaluated with three quantitative sensory testing methods.

Methods and Results

Pressure pain thresholds, electrical pain thresholds and tolerance to the cold pressor test were measured before and 2 hours after the intravenous administration of 2 ng/kg purified E. coli endotoxin in 27 healthy volunteers. Another 20 subjects not exposed to endotoxemia served as controls. Endotoxemia led to a rise in body temperature and inflammatory symptom scores and a rise in plasma TNF-α, IL-6, IL-10 and IL-1RA. During endotoxemia, pressure pain thresholds and electrical pain thresholds were reduced with 20±4 % and 13±3 %, respectively. In controls only a minor decrease in pressure pain thresholds (7±3 %) and no change in electrical pain thresholds occurred. Endotoxin-treated subjects experienced more pain during the cold pressor test, and fewer subjects were able to complete the cold pressor test measurement, while in controls the cold pressor test results were not altered. Peak levels and area under curves of each individual cytokine did not correlate to a change in pain threshold measured by one of the applied quantitative sensory testing techniques.

Conclusions and Significance

In conclusion, this study shows that systemic inflammation elicited by the administration of endotoxin to humans, results in lowering of the pain threshold measured by 3 quantitative sensory testing techniques. The current work provides additional evidence that systemic inflammation is accompanied by changes in pain perception.     

Thresholds for 60 Hz magnetic field stimulation of peripheral nerves in human subjects

The goal of the research reported here is to narrow the range of uncertainty about peripheral nerve stimulation (PNS) thresholds associated with whole body magnetic field exposures at 50/60 Hz. This involved combining PNS thresholds measured in human subjects exposed to pulsed magnetic gradient fields with calculations of electric fields induced in detailed anatomical models of the body by that same exposure system. PNS thresholds at power frequencies (50/60 Hz) can be predicted from these data due to the wide range of pulse durations (70 mus to 1 ms), the length of the pulse trains (several tens of ms), and the exposure of a large part of the body to the magnetic field. These data together with the calculations of the rheobase electric field exceeded in 1% (E(1%)) of two anatomical body models, lead to a median PNS detection threshold of 47.9 +/- 4.4 mT for a uniform 60 Hz magnetic field exposure coronal to the body. The threshold for the most sensitive 1% of the population is about 27.8 mT. These values are lower than PNS thresholds produced by magnetic fields with sagittal and vertical orientations or nonuniform exposures.     

A Novel Magnetic Stimulator Increases Experimental Pain Tolerance in Healthy Volunteers - A Double-Blind Sham-Controlled Crossover Study

The ‘complex neural pulse’^TM (CNP) is a neuromodulation protocol employing weak pulsed electromagnetic fields (PEMF). A pioneering paper reported an analgesic effect in healthy humans after 30 minutes of CNP-stimulation using three nested whole head coils. We aimed to devise and validate a stimulator with a novel design entailing a multitude of small coils at known anatomical positions on a head cap, to improve applicability. The main hypothesis was that CNP delivery with this novel device would also increase heat pain thresholds. Twenty healthy volunteers were enrolled in this double-blind, sham-controlled, crossover study. Thirty minutes of PEMF (CNP) or sham was applied to the head. After one week the other treatment was given. Before and after each treatment, primary and secondary outcomes were measured. Primary outcome was heat pain threshold (HPT) measured with thermal quantitative sensory testing. Other outcomes were warmth detection threshold, and aspects of cognition, emotion and motor performance. As hypothesized heat pain threshold was significantly increased after the PEMF stimulation. All other outcomes were unaltered by the PEMF but there was a trend level reduction of cognitive performance after PEMF stimulation as measured by the digit-symbol substitution task. Results from this pilot study suggest that our device is able to stimulate the brain and to modulate its function. This is in agreement with previous studies that used similar magnetic field strengths to stimulate the brain. Specifically, pain control may be achieved with PEMF and for this analgesic effect, coil design does not appear to play a dominant role. In addition, the flexible configuration with small coils on a head cap improves clinical applicability.

Trial Registration

Dutch Cochrane Centre NTR1093     

Chronic exposure of primates to 60-Hz electric and magnetic fields: III. Neurophysiologic effects

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.     

Quantification of gender specific thermal sensory and pain threshold before and after laser needle stimulation]

Quantitative thermal sensory and pain threshold testing (QST) was performed in 29 adult healthy volunteers (mean age 24.2 +/- 2.7 years; range: 18-29 years; 20 females, 9 males) using the Thermal Sensory Analyser TSA-II (Medoc Advanced Medical Systems, Ramat Yishai, Israel, and Minneapolis, Minnesota, USA) before and after laser needle acupuncture and placebo stimulation, respectively. Significant (p < or = 0,001; t-test) gender-specific differences were seen on cold pain threshold analysis. No significant changes in parameters of thermal sensory and pain thresholds were found before and after laser needle or placebo stimulation at acupuncture points for acute pain. However, a trend towards change in the median value of cold pain sensation after laser needle stimulation (p = 0.479; paired t-test; n.s.) was seen within the group of healthy females. The influence of stimulation of acupuncture points for chronic pain on the various parameters needs to be clarified in future studies.     

躯体感觉Ⅱ区皮层内微刺激对猕猴回避性操作式条件反射和针刺镇痛的影响

在七只清醒、可以活动的猕猴上观察了皮层内刺激 S_Ⅱ区对外周痛阈和针刺镇痛的影响,其结果如下:(1)在73次皮层内刺激的实验中有72次引起对侧相应皮肤感受野的痛阈变化,其中54次痛阈明显升高。痛阈升高的效应在停止刺激后常持续0.5—3min。较浅层的刺激,痛阈升高比较明显;不同刺激强度引起的痛阈升高的程度也不相同。(2)一般皮层内刺激 S_Ⅱ区也可导致同侧相应皮肤感受野痛阈升高,但不如对侧痛阈升高明显。(3)皮层内刺激 S_Ⅱ区时,非感受野痛阈几乎没有任何改变。(4)S_Ⅱ区皮层内刺激可增强针刺镇痛效应。