Pain
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Several studies of experimental and acute clinical pain have indicated reactive effects of self-assessment on pain intensity and tolerance. A recent study of chronic pain patients (vonBaeyer 1994), however, failed to show these effects. The present investigation sought to determine whether reactive effects can be produced in chronic pain patients by an intensive self-assessment protocol. ⋯ Using repeated measures analysis of the daily means, no significant effects of time were found for any measures. Reactive effects that result in an average change in pain levels over time, therefore, do not appear to be produced by intensive self-assessment in a naturalistic context. Results are discussed in terms of cognitive and behavioral theories of pain reactivity.
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Migraine is a common and debilitating condition. Its treatment has received considerable attention in recent times with the introduction into clinical use of the serotonin (5HT)1B/D-like agonist sumatriptan. It is known from human studies that the intracranial blood vessels and dura mater are important pain-sensitive structures since mechanical or electrical stimulation of these vessels, such as the superior sagittal sinus, causes pain. ⋯ These effects were dose-dependent and were significantly different from the effect of vehicle (P < 0.05). These data demonstrate that systemically administered zolmitriptan can inhibit evoked trigeminovascular activity within the trigeminal nucleus. This inhibition of trigeminal activity may play a role in the anti-migraine actions of this compound and offers the prospect of a third pathophysiologically consistent target site for anti-migraine drug effects.
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Inflammation of the temporomandibular joint (TMJ) region evokes pain and hyperalgesia as well as causing persistent changes in the response properties of central trigeminal neurons. To determine if excitatory amino acids have a role in TMJ-induced responses, extracellular concentrations were measured in microdialysate samples from probes positioned in the spinal trigeminal nucleus (Vsp) near the transition region between subnucleus interpolaris and subnucleus caudalis (Vi/Vc) in chloralose-anesthetized rats. Injection of the selective small fiber excitant, mustard oil (20 microliters, 20% solution), into the ipsilateral TMJ region caused a transient (by 10 min) increase in glutamate (from 0.48 +/- 0.16 to 1.94 +/- 0.78 microM, P < 0.005) and aspartate (from 0.29 +/- 0.11 to 1.78 +/- 0.82 microM, P < 0.025) among sites located at the ventrolateral pole of the Vi/Vc transition region (n = 6). ⋯ Addition of high potassium (150 mM) to the perfusate solution caused increases in glutamate and aspartate regardless of probe location. The transient and selective release of glutamate and aspartate within the Vi/Vc transition after acute irritation of the TMJ region is consistent with a proposed role for excitatory amino acids in mediating noxious sensory input from deep orofacial structures. Together with previous reports of c-fos expression, these results suggest that neurons within the ventrolateral portion of the Vi/Vc transition may serve as a relay site for the integration of sensory or reflex responses to acute inflammation of the TMJ region.
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Randomized Controlled Trial Clinical Trial
Lack of effect of transcutaneous electrical nerve stimulation upon experimentally induced delayed onset muscle soreness in humans.
The aim of the current study, for which ethical approval was obtained, was to assess the hypoalgesic efficacy of transcutaneous electrical nerve stimulation (TENS) upon acute stage (72 h) experimentally induced delayed onset muscle soreness (DOMS). TENS naive subjects (n = 48; 24 male and 24 female) were recruited, screened for relevant pathology and randomly allocated to one of four experimental groups: control, placebo, low TENS (200 microseconds; 4 Hz) or high TENS group (200 microseconds; 110 Hz). DOMS was induced in a standardised fashion in the non-dominant elbow flexors of all subjects by repeated eccentric exercise. ⋯ Measurements were taken before and after treatment under controlled double blinded conditions. Analysis of results using repeated measures analysis of variance (ANOVA) and post hoc tests showed some inconsistent isolated effects of high TENS (110 Hz) compared to the other conditions upon resting angle and flexion scores; no significant effects were found for any of the other variables. These results provide no convincing evidence for any measurable hypoalgesic effects of TENS upon DOMS-associated pain at the stimulation parameters used here.
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To examine the pathophysiological mechanisms of vascular disturbances and to assess the role of the sympathetic nervous system, 12 patients with reflex sympathetic dystrophy (RSD) of the hand were studied using laser Doppler flowmetry. Cutaneous blood flow, skin resistance and skin temperature were measured at the affected and contralateral hands. Sympathetic vasoconstrictor reflexes were induced bilaterally by deep inspiration. ⋯ Therefore, they have to be interpreted with care when defining reliable diagnostic criteria. (2) Vascular disturbances in RSD are not due to constant overactivity of sympathetic vasoconstrictor neurons. Changes in vascular sensitivity to cold temperature and circulating catecholamines may be responsible for vascular abnormalities. Alternatively, RSD may be associated with an abnormal (side different) reflex pattern of sympathetic vasoconstrictor neurons due to thermoregulatory and emotional stimuli generated in the central nervous system. (3) After sympathectomy, denervation supersensitivity of blood vessels and intense vasomotion may be associated with recurrence of pain in some patients.