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At least 307 records · Page 17Linked to original sources
PubMed1989

Threshold tracking for assessment of long-term adaptation and sensitization in pain perception.

To assess temporal variations in the perception of "phasic" heat pain stimuli a psychophysical tracking procedure was developed that enables repeated assessment of the pain threshold at short intervals. This "double-tracking" procedure produces two tracking curves simultaneously, one that approaches the pain threshold gradually from above, the other from below. The threshold for phasic heat pain was measured in 80 tracking trials with stimuli at temperatures near the pain threshold. Concurrently, the threshold for "tonic" heat pain was determined after every 20 tracking trials with a stimulus adjustment procedure. Eleven healthy subjects (age: 26.4 yr. +/- 6.0) participated in 2 sessions each. Phasic stimulation near the pain threshold did not produce any trends in either of the two threshold measures. Hence there was no long-term adaptation or sensitization. However, there were random variations (random walks) in the tracking curves, which we interpret as resulting from a stochastic relationship between stimulus and sensation. In agreement with other reports, discrimination seemed to be better at painful than at nonpainful temperatures.

Adaptation, Physiological↗
PubMedDate not supplied

Psychosocial influences on pain perceptions in cancer.

This article provides an overview of the literature on the psychological and social factors that may affect a patient's perception and expression of pain. The author examines the experiences of people with cancer pain and looks at a range of factors, such as age and culture, that affect how patients perceive and describe their pain.

Adaptation, Psychological↗
PubMed1998

Cannabinoid transmission and pain perception.

The use of cannabis for the management of a wide range of painful disorders has been well documented in case reports throughout history. However, clinical evaluations of cannabis and its psychoactive constituent THC have not led to a consensus regarding their analgesic effectiveness. On the other hand, THC and its synthetic derivatives have been shown to be effective in most animal models of pain. These antinociceptive effects are mediated through cannabinoid receptors in the brain that in turn appear to interact with noradrenergic and kappa opioid systems in the spinal cord to modulate the perception of painful stimuli. The endogenous ligand, anandamide, is also an effective antinociceptive agent. The extent to which the endogenous cannabinoid system is involved in the modulation of pain is currently unknown.

Analgesics↗
PubMedDate not supplied

The dynamics of pain perception in conditions of purposive activity.

Pain threshold sensitivity determination and recording of somatosensory evoked potentials in response to electrical skin stimulation were used to study the dynamics of pain sensitivity in medical students in mid-semester before blood donor and examination procedures and in the post-procedure period during performance of an editing test. Increases in pain sensitivity thresholds were seen in all subjects during the examination period and on performance of the editing test. Differences in changes in evoked potential amplitudes were found, depending on the individual-typological characteristics of the nervous system and the quality of motivationally determined states. Subjects with different individual-typological characteristics had different subjective pain sensation dynamics in test conditions.

Adolescent↗
PubMed1980

Altered pain perception in hypertensive humans.

Sensory and pain thresholds to electrical stimulation of tooth pulps were measured in normotensive and essential hypertensive unmedicated human subjects. In both adult and young subjects there was a significant correlation between blood pressure and pain sensitivity: hypertensives had a higher threshold for sensation of pain in the tooth-pulp test than normotensive controls. An interrelationship between blood pressure and pain regulation is suggested.

Adolescent↗
PubMed1986

Pain perception decrement produced through repeated stimulation.

Pain responses (pain detection and pain discomfort) to electrical dental stimulation were studied in 16 normal subjects. The repetition of the dental stimuli induced a significant and long-lasting (60 min) decrease in pain sensitivity at both sensory levels (after 60 min of repetitive stimulation, 79% increase in pain detection, P less than 0.0001, 45% increase in pain discomfort, P less than 0.0004). The sensory response decrement through repeated elicitation was not influenced by naloxone administration (1.2 mg i.m.). This study clearly demonstrates the induction of pain sensory decrease through repetitive stimulation which differs from peripheral sensory receptor adaptation, from the inhibitory gating mechanism or from diffuse inhibitory controls activation; its unresponsiveness to naloxone suggests that this phenomenon is not opioid-dependent. A technique has been standardized which will enable the systematic study of pain decrease under sustained nociceptive stimulation in chronic pain patients.

Double-Blind Method↗
PubMed1994

Objective evaluation of pain perception in patients with schizophrenia.

The pain thresholds of patients with schizophrenia often seem to differ from those of healthy subjects. In the present study we assessed the pain thresholds of ten patients with schizophrenia, and of ten controls, by measuring the leg flexion nociceptive reflex threshold: the stimulation threshold at which this reflex is triggered, is known to be correlated with the pain threshold. Our conclusion is that, in most cases, the increase in pain threshold is the result of 'attitude' and not of alterations in brain function.

Adult↗
PubMed1982

[Neurophysiological mechanisms of pain perception].

Information on noxious stimuli is perceived in the periphery by free nerve endings and conveyed to the spinal cord by A delta and C-fibres. They mostly terminate within the substantia gelatinosa (SG) of the dorsal horn. Within this structure, transmission of pain information is modified by serotoninergic and enkephalinergic mechanisms. Neurones from the deeper layers of the dorsal horn relay pain information via the ventrolateral tract to the brain stem reticular formation and thalamic nuclei. From there, pathways to the somatosensory cortex, basal ganglia, and limbic structures were described, which probably mediate conscious perception, subconscious motor reactions and emotional colouring of pain perception, respectively. For the efferent control of pain transmission, the periaqueductal gray matter (PGM) is the central structure. Electrical stimulation of PGM can relieve patients at least temporarily from states of chronic pain. PGM is connected to the midbrain raphe nuclei, from where serotoninergic fibres descend to the spinal cord to modify pain transmission in neurones within SG. Enkephalin is present in the terminals of SG interneurones and reduces pain transmission by acting on opiate receptors on the terminals of nociceptive primary afferents and probably also postsynaptic sites. Analgesia produced by natural or electrical stimulation of other cutaneous afferents and by acupuncture is believed to be mediated by these enkephalin-containing interneurones within SG of the dorsal horn.

Analgesia↗
PubMed1995

Sensory information can decrease cold-induced pain perception.

Specific terms are often used to describe the pain athletes typically experience during cold treatments. It is not clear whether providing athletes with such descriptive sensory information will decrease their perceived pain during treatments. The purpose of this study was to determine if subjects' perceptions of cold-induced pain could be influenced by the type of information provided before treatment, such as "pain will be cursing" or "pain will be flickering." Ninety Division I intercollegiate athletes were randomly assigned to one of five groups: traditional terms (cold, burning, aching, numbness), high-level terms (freezing, crushing, pounding, heavy), moderate-level terms (cold, gnawing, pulsing, aching), or low-level terms (cool, pinching, flickering, dull) from the McGill Pain Questionnaire, or no terms at all (control). The four groups that received a set of terms were told that those terms described the sensations they would feel during cold immersion of the ankle. Pain was measured with the McGill Pain Questionnaire every 3 minutes during a 21-minute immersion (1 degrees C) of the foot and ankle. Sensory, affective, evaluative, and miscellaneous pain measures were derived. The control group experienced greater sensory and affective pain than did any of the other groups and experienced greater evaluative pain than did the groups receiving low-level or traditional terms. We conclude that providing athletes with some type of sensory information to describe their cold-pain experience will decrease their perceived pain during cold immersion, although it does not seem to matter what terms are used.

Journal Article↗
PubMed1999

Effects of distraction on pain perception: magneto- and electro-encephalographic studies.

After a painful CO2 laser stimulation to the skin, the magnetoencephalography (MEG) response (164 ms in average peak latency) was not affected by distraction, but the sequential electroencephalography (EEG) responses (240-340 ms), probably generated by a summation of activities in multiple areas, were markedly affected. We suspect that the MEG response, whose dipole is estimated in the bilateral second somatosensory cortex (SII) and insula, reflects the primary activities of pain in humans.

Adult↗
PubMed1992

Site and mechanism of pain perception with oesophageal balloon distension and intravenous edrophonium in patients with oesophageal chest pain.

Ten healthy volunteers and 13 patients with oesophageal motility disorders whose primary presenting complaint was chest pain were studied by distending an intraoesophageal balloon in 1 ml steps to the point of a sensation of discomfort. The net balloon pressure (intra-balloon pressure when inflated within the oesophagus minus the pressure recorded at the same volume outside the patient) was measured at each volume increment and the distension volume at the perception of discomfort was noted. The measurements were repeated after intravenous injection of edrophonium (80 micrograms/kg) and again after 1.2 mg intravenous atropine. Oesophageal wall compliance was similar in patients and controls, and the two groups showed a similar effect of decreased compliance with edrophonium and increased compliance after atropine. There were no significant differences between patients and controls of distending volume at perception of discomfort. Edrophonium, however, resulted in a significant reduction in distension threshold for pain (p less than 0.03) in patients. A similar though non-significant trend was seen in controls. In both controls and patients, distension volume for pain production after atropine was significantly (p less than 0.01) higher than after edrophonium. From these results and other published data, we suggest that the pain receptor for noxious stretch and after edrophonium challenge is likely to be an 'in series' mechanoreceptor located in oesophageal longitudinal muscle.

Adult↗
PubMed1999

Central modulation of pain perception.

The information presented in this article provides a basis for individual variability in the sensation of pain and the behavioral correlates associated with pain. The knowledge of pain-inhibitory and pain-facilitating pathways linked to cognitive, emotional, and stress-response systems leads to a greater understanding of the complexities of the experience of pain. Appreciation of the influence of these higher centers should lead to improvements in the clinical management of pain.

Brain↗