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At least 163 records · Page 9Linked to original sources

Age-associated change in pain threshold measured by transcutaneous neuronal electrical stimulation.

The measurement of cutaneous pain threshold using the Neuromod Selectra Model 7750 Transcutaneous Neuronal Electrical Stimulator is described. Pain threshold, measured in 520 healthy volunteers aged 5-105 years, increased with age. Consistent values were obtained in 22 healthy volunteers on three successive days. Pain threshold may be rapidly measured by this method which is potentially of value in the assessment of patients with neurological deficits.

Adolescent↗

Argon laser induced cutaneous sensory and pain thresholds in post-herpetic neuralgia. Quantitative modulation by topical capsaicin.

Sensory and pain thresholds to cutaneous argon laser stimulation were determined in patients with post-herpetic neuralgia before and during treatment with topical capsaicin. Before treatment both thresholds were significantly elevated on the affected side compared to the contralateral normal area. After one week of capsaicin treatment both thresholds were significantly increased compared to the pre-treatment values, and the subjective pain relief, measured on a visual analogue scale (VAS) was 24%. More than 10% decrease in VAS pain score was obtained by 62.5% of the patients. Laser stimulations at levels at which the sensory and pain thresholds are reached were initially described as burning or stinging with pain projecting outside the stimulated area. This allodynia to laser stimulations changed during capsaicin treatment towards normal sensory and pain perception qualities. Both sensory and pain thresholds and the subjective pain score evaluated on a visual analogue scale were attenuated during the capsaicin treatment, suggesting a significant role of the cutaneous sensory and pain receptors in postherpetic neuralgia.

Administration, Topical↗

Influence of muscle pain tolerance on muscle pain threshold in experimental tooth clenching in man.

Ten adults and ten children exercised maximal voluntary tooth clenching until pains appeared in the jaw muscles, i.e. the muscle pain threshold of tooth clenching was determined. Subsequently, the subjects were instructed to exercise tooth clenching until they were forced to stop because of intolerable pains and exhaustion of the contracting muscles, i.e. the muscle pain tolerance of tooth clenching was recorded, and during these bouts of clenching the pain tolerance of tooth clenching was recorded, and during these bouts of clenching the pain threshold was also determined. In adults, determination of the pain tolerance decreased the pain threshold by 19%, and in children it either decreased the pain threshold by 20% or increased it by 56%. It is proposed to introduce the muscle pain tolerance of tooth clenching as an adjunct in the clinical examination of cases of facial pains presumed to originate from the jaw muscles, but the test should be interpreted with caution.

Adolescent↗

[The effect of extradural injection of capsaicin on pain threshold and electroacupuncture analgesia of rat].

The present paper is designed to investigate the variation of pain threshold and electroacupuncture analgesia of rat, and to observe the immunohistochemical changes in spinal ganglion and dorsal horn of lumber and sacral segment of spinal cord after extradural administration of capsaicin (100 micrograms/rat). It was found: 1. Obvious decrease of pain threshold 60 mins after injection of capsaicin, and the pain threshold restored nearly to the level of pre-treatment at 90 mins of post-treatment of capsaicin. 2. Apparent elevation of pain threshold on 1st-15th day after injection of capsaicin. 3. The efficiency of electroacupuncture analgesia 7th day after injection of capsaicin was obviously weaker than that of pre-treatment of drug and that of solvents treatment in the animals of control group. 4. The SP-LI, ENK-LI and FRAP were all weakened in dorsal horn of spinal cord 1h after capsaicin treatment. However, on the 7th day, with the exception of decrease of SP-LI and FRAP, the ENK-LI in dorsal horn was strengthened and the activity of FRAP in spinal ganglionic cells of B type disappeared. The foregoing results indicated that the metabolism and function of C fibers of primary afferent especially the SP containing nerve and those of ENK-containing neurons could be influenced by the extradural injection of capsaicin. And the primary afferent C fiber (including the SP containing nerve) may play important roles in the input of the informations of pain, and needling, as well as in the acupuncture analgesia.

Acupuncture Analgesia↗

Increase in muscular pain threshold following low frequency-high intensity peripheral conditioning stimulation in humans.

The effects of low frequency-high intensity transcutaneous and intramuscular electrical nerve stimulation (TENS and IENS, respectively) on ipsilateral muscular pain threshold were studied in healthy volunteers. The combined effects of TENS (or IENS) and vibration as well as the effects of TENS applied to contralateral regions were also investigated. Muscular pain threshold was evaluated by the subjects' verbal reports in response to electrical stimulation (wire electrodes) of the vastus medialis muscle and by the appearance of blink response (startle reaction) without habituation. TENS was generally applied to the skin overlying the same muscle, and in some instances to the skin overlying the contralateral vastus medialis or triceps muscle. IENS was performed through the same electrodes used for inducing muscular pain. Vibration was applied to the tendon of ipsilateral quadriceps femoris muscle. TENS consistently induced marked and long-lasting elevations of ipsilateral muscular pain threshold. Comparable results were obtained by IENS. TENS and vibration performed simultaneously induced increases in muscular pain threshold, which were greater than those obtained with each individual conditioning stimulation. TENS proved to be capable of enhancing muscular pain threshold even when applied to contralateral regions; however, these effects were smaller and of shorter duration. The results provide evidence that low frequency-high intensity TENS (or IENS) are effective in raising muscular pain threshold and support the hypothesis that this type of stimulation brings supraspinal control systems into action through the activation of group III afferent fibres.

Adult↗

Extracephalic tenderness and pressure pain threshold in children with headache.

BACKGROUND: Sensitisation of the pain detection system has been suggested to be involved in the pathogenesis of recurrent headache. In adults, increased sensitivity to pain has been found in patients with chronic tension type headache. Children with migraine or with unspecific headache report non-headache pains and interictal pericranial muscular tenderness more often than headache-free children. OBJECTIVE: To study if children with different types of headache report non-headache pain more often than children with no headache and if extracephalic muscular tenderness is different in children with headache in comparison to headache-free children. To find out if interval to the headache episode has influence on the extracranial muscular tenderness. DESIGN: A population-based sample of 13-year-old children with migraine (n=48), episodic tension type headache (61) or no headache (59) were interviewed for the occurrence and characteristics of headache and fulfilled a questionnaire on non-headache pain. A structured manual palpation test on muscular tenderness and a pain threshold measurement were done on seven cephalic and three extracephalic points. RESULTS: Children with migraine reported other pains, especially stomach pain and limb pain more often than children with episodic tension type or no headache. There were no significant differences in the extracephalic muscular tenderness or in the pressure pain thresholds between the three groups. CONCLUSIONS: Children with migraine experience more non-headache pains than children with episodic tension type headache and with no headache. However, neither children with migraine nor children with episodic tension type headache show increased interictal extracephalic muscular sensitivity for palpation.

Abdominal Pain↗

Response of C fibre nociceptors in the anaesthetized monkey to heat stimuli: correlation with pain threshold in humans.

1. Ramped heat stimuli were used to compare the effects of rate of temperature change on the responses of monkey nociceptors and on heat pain threshold in human subjects. Recordings were made from twenty-five cutaneous C fibre mechano-heat nociceptors (CMHs) innervating the hairy skin in the anaesthetized monkey. Heat pain thresholds were determined on the volar forearm of eight human subjects using a converging staircase technique. 2. The heat pain threshold decreased as stimulus ramp rate increased. In contrast, the CMH heat threshold, defined as the surface temperature at which the first action potential occurred, increased as stimulus ramp rate increased. Thus, the properties of the heat stimulus that dictate heat pain threshold are different from the properties of the heat stimulus that govern the initiation of a response in nociceptors. 3. Peak discharge frequency of CMHs during the heat ramp increased with stimulus ramp rate. Heat pain threshold was correlated with achievement of a minimum discharge rate in nociceptors (0.5 Hz), rather than with the threshold for action potential initiation.

Action Potentials↗

Exercise lowers pain threshold in chronic fatigue syndrome.

Post-exertional muscle pain is an important reason for disability in patients who are diagnosed to have Chronic Fatigue Syndrome (CFS). We compared changes in pain threshold in five CFS patients with five age and sex matched controls following graded exercise. Pain thresholds, measured in the skin web between thumb and index finger, increased in control subjects with exercise while it decreased in the CFS subjects. Increased perception of pain and/or fatigue after exercise may be indicative of a dysfunction of the central anti-nociceptive mechanism in CFS patients.

Adult↗

Effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold.

This study compared the effects of unilateral and bilateral auricular transcutaneous electrical nerve stimulation on cutaneous pain threshold. Auricular acupuncture points were stimulated with low frequency, high intensity TENS for 45 seconds. Sixty healthy, adult subjects were assigned randomly to one of two treatment groups or to a control group. The two treatment groups received low frequency, high intensity TENS either unilaterally or bilaterally. The control group did not receive auricular stimulation. Experimental pain threshold at the left wrist was determined with a painful stimulus before and after auricular stimulation. Both unilateral and bilateral auricular stimulation groups exhibited a significant increase (p less than .05) in experimental pain threshold, but the control group did not. The mean change values between the unilateral and bilateral stimulation groups were not statistically different. These results suggest that both unilateral and bilateral auricular TENS can increase pain threshold.

Adult↗

Increase of the heat pain threshold during and after high-frequency transcutaneous peripheral nerve stimulation in a group of normal subjects.

AIM: Transcutaneous electrical nerve stimulation (TENS) is used worldwide for pain relief, but its mechanisms of action are not completely understood. High frequency transcutaneous peripheral nerve stimulation (HF-TPNS) is a term describing a type of TENS where a peripheral nerve is stimulated transcutaneously. The aim of the investigation was to verify the hypothesis that HF-TPNS increases the heat pain threshold in the skin territory of the stimulated nerve, during and after stimulation. METHODS: Eighteen volunteers (8 men, 10 women) participated in 2 sessions conducted on different days. In each session their heat pain thresholds were measured in basal conditions and after 5, 10, 15, 25, 40, 70 min. In one session, HF-TPNS was delivered for 10 min immediately after basal evaluation (HF-TPNS session). In the other session the heat pain thresholds only were measured (control session). The superficial radial nerve was stimulated at the wrist (frequency of 100 Hz, pulse duration of 0.1 ms). The heat pain threshold was studied using a contact thermode (surface of 12.5 cm(2)) placed in the cutaneous area of the stimulated nerve at the site where the paresthesia evoked by electrical stimulation could be felt. RESULTS: HF-TPNS significantly increased the heat pain threshold both during and after stimulation. CONCLUSION: This study confirms that HF-TPNS induces an important hypoalgesic effect. The prolonged duration of poststimulation hypoalgesia (60 min) indicates that continuous stimulation is probably unnecessary. Further studies are needed to test the hypothesis that intermittent HF-TPNS is able to maintain its hypoalgesic effectiveness over time.

Adult↗

Effects of calcitonin injected into various brain areas on pain threshold and Ca2+ in rats.

AIM: To study the effects of calcitonin (Cal) injected into different brain areas on pain threshold. METHODS: The analgesic effects of Cal were investigated in rats by the tail-flick test. RESULTS: Cal injected into lateral cerebral ventricle (LCV) or periaqueductal gray (PAG) increased obviously the pain threshold to 49 +/- 22% or to 68 +/- 12% (P < 0.01), respectively. When PAG was blocked with lidocaine, the analgesic effect of Cal injected into LCV was lowered 41 +/- 9%. Cal injected into habenula (Hab) decreased the pain threshold to -30 +/- 5% (P < 0.01). CONCLUSION: Cal in different rat brain areas induced different effects on pain responses: analgesia or hyperalgesia, and showed that PAG played an important role in the analgesic effect induced by Cal, and the changing of pain threshold was mediated by the Ca2+ in brain.

Analgesics, Non-Narcotic↗

The effects of delta wave sleep interruption on pain thresholds and fibromyalgia-like symptoms in healthy subjects; correlations with insulin-like growth factor I.

OBJECTIVE: To assess the effects of delta wave sleep interruption (DWSI) on pain thresholds and fibromyalgia-like symptoms. To examine the potential correlations between DWSI and serum insulin-like growth factor 1 (IGF-1). METHODS: Thirteen healthy volunteers were subjected to 3 consecutive nights of DWSI (Group 1). Pain thresholds were measured by dolorimetry and symptoms by visual analog scale. Six subjects not undergoing DWSI served as dolorimetry and symptom controls (Group 2). Serum IGF-1 was measured by competitive binding radioimmunoassay before and after DWSI. RESULTS: No significant differences in pain thresholds as a function of condition (baseline, DWSI, recovery) or overnight change were detected between or within groups (p>0.05). Morning mean dolorimeter scores were lower than evening scores in both groups during all 3 conditions, and were lower in Group 1 than in Group 2 during DWSI. Group 1 subjects had higher composite symptom scores during DWSI (p< or =0.005), attributed largely to increases in fatigue. Serum levels of IGF-1 from Group 1 subjects showed no significant change after DWSI (p>0.05). CONCLUSION: In our study subjects, 3 nights of DWSI caused no significant lowering of pain thresholds compared with a control group. Subjects appeared to have lower pain thresholds in the mornings, and DWSI appeared to augment this effect. Symptoms were more apparent during DWSI, but were primarily related to fatigue. IGF-1 was not altered by 3 nights of DWSI. The low levels of IGF-1 seen in patients with fibromyalgia syndrome may result from chronic rather than acute DWSI, or may be dependent on factors other than disturbances of delta wave sleep.

Adolescent↗

Effect of intracerebroventricular injection of somatostatin or GABA on pain threshold and contents of GABA or somatostatin in rat brain.

AIM: To study the interactive influence of somatostatin (Som) and GABA in the brain and its relation to the pain modulation. METHOD: Using radioimmunoassay, amino acid analyzer and measurement of pain threshold. RESULTS: Som 10 micrograms i.c.v. increased the pain threshold (from 4.2 +/- 0.2 to 7.0 +/- 1.1 s) of the rat, but reduced the content of GABA from 2.3 +/- 0.3 to 1.6 +/- 0.4 mumol g-1 in hippocampus and from 2.4 +/- 0.4 to 1.5 +/- 0.2 mmol kg-1 in brain stem. After depletion of the Som in brain by i.c.v. cysteamine (Cys, 600 micrograms), the content of GABA in hippocampus and brain stem was also reduced without modification of the pain threshold. GABA 1500 micrograms i.c.v. had no effect on the pain threshold, however, caused a decrease of Som content from 55 +/- 4 to 37 +/- 5 ng g-1 in hippocampus and from 84 +/- 4 to 55 +/- 6 ng g-1 in brain stem, which was blocked by bicuculline (10 micrograms). After reduced of the GABA content in brain by subcutaneous injection of isoniazid (300 mg kg-1), Som content of the hippocampus and rain stem was markedly elevated. CONCLUSION: Som and GABA inhibited each other, unrelated to their pain modulation.

Animals↗

[Effect of monoamine neurotransmitters, enkephalin and morphine on substance P contents of several brain regions and pain threshold in rats].

The present work was carried out to observe the effect of intra-cerebroventricular (icv) injection of monoamine neurotransmitters, enkephalin and morphine on immunoreactive substance P(Ir-SP) contents in hypothalamus, striatum, hippocampus and pain threshold. The results were as follows: (1) After icv or intra-DR (dorsal raphe nucleus) injection of 5-HTP, the content of Ir-SP in hypothalamus significantly decreased and pain threshold markedly increased; After depletion of the 5-HT content in brain by pCPA or destruction of DR, the contents of Ir-SP were remarkably elevated in three brain regions by the former and in hypothalamus, striatum by the later. (2) The Ir-SP levels in the three brain regions and the pain threshold were not affected by the icv injection of NE, however, icv injection of DA caused a increase of Ir-SP concentration in striatum which was reversed by the DA receptor antagonist haloperidol, but without any change of the pain threshold. 7th day after icv injection of 6-OHDA, the content of Ir-SP in striatum significantly reduced. (3) Icv injection of met-enkephalin (MEK) or morphine could increase the Ir-SP levels in hypothalamus, striatum and the pain threshold, and above-mentioned effect of morphine could be prevented by the opioid receptor antagonist naloxone. Icv injection of leu-enkephalin (LEK) had no effects both on Ir-SP contents in three brain regions and the pain threshold.

Animals↗

Effect of high-frequency vibration on experimental pain threshold in young women when applied to areas of different size.

The purpose of this study was to compare the effects of high-frequency vibration when applied to two areas of different size. Subjects were 30 right-handed Caucasian women, aged 19-38 years, with a negative history of upper extremity dysfunction. The experimental cutaneous pain threshold was determined by stimulating the skin over the pisiform bone on the palmar surface of the hand. Pain threshold measurements were taken before, during, and 2 and 5 min after vibration. Group A received vibration to an area 12.5 cm2 on the ulnar aspect of the palm of the hand 1 cm distal to the pisiform bone. Group B received vibration to an area 25 cm2, also on the ulnar aspect of the palm of the hand. Results of the mixed design analysis of variance performed on the mean pain thresholds indicate that there was no significant main effect for group (size of area vibrated), p greater than 0.05, or interaction effect between group by trial (size of area vibrated and time of pain threshold measurement), p greater than 0.05. There was a significant main effect for trial (time of pain threshold measurement), p less than 0.001. Pain threshold values were greatest for both groups during the period of vibration.

Adult↗

Electroacupuncture increases ipsilaterally tooth pain threshold in man.

The effect of electroacupuncture stimulation applied to a unilateral Ho-ku point on the human tooth pain thresholds was studied by electrically stimulating bilateral canines. In six of ten subjects tested, the tooth pain threshold was elevated ipsilaterally but was unchanged contralaterally during and after the electroacupuncture. In the remaining four, neither the ipsilateral nor the contralateral canine showed any change in the pain threshold by the electroacupuncture. The ipsilateral increase of the tooth pain threshold may be explained by a mechanism by which electroacupuncture stimulation of one Ho-ku point causes various pain suppression centers to release ipsilaterally endogenous opioids.

Acupuncture Therapy↗

The effects of stimulus area and adaptation temperature on warm and heat pain thresholds in man.

The effect of stimulus area and adaptation temperature on warm and heat pain threshold were studied in healthy human subjects using a contact thermal stimulator. The stimulus area was varied in the range of 1.3 to 11.8 cm. Both the warm and heat pain thresholds decreased with increasing stimulus surface. Heat pain and warm thresholds were equally affected by the stimulus surface. The adapting temperature was varied in the range 25-35 degrees C, and warm thresholds were elevated with increasing adaptation temperature. The change of heat pain thresholds with increasing adapting temperature was not significant. Thus, there are both differences and similarities concerning how the different stimulus conditions affect heat pain and warm thresholds.

Adaptation, Physiological↗