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Biomedical subjects

R Dubner

Publications and source records attributed to R Dubner.

At least 127 records · Page 7Linked to original sources
PubMed1982

Fentanyl reduces the intensity of painful tooth pulp sensations: controlling for detection of active drugs.

This study assessed whether experimentally determined narcotic analgesia in human subjects represents a pharmacologic effect or a psychological effect of detecting the administration of an active medication. Forty dental patients used a verbal descriptor procedure to assess both the intensity and unpleasantness of sensations produced by electrical stimulation of intact teeth. Stimuli were rated before and after an intravenous injection og 0.11 mg/kg of diazepam, to produce detectable side effects in all patients, followed by a double-blind intravenous injection of either 0.66 microgram/kg of fentanyl or saline placebo. The results were similar to previous findings in which diazepam was not administered: only intensity responses were reduced after fentanyl administration and only unpleasantness responses were reduced after placebo administration. These results suggest that the reduction in pain intensity following fentanyl administration represents an analgesic effect and not an artifact of detecting the administration of an active medication. They also suggest that diazepam at this dose does not alter pain sensations produced by electrical tooth pulp stimulation.

Adolescent↗
PubMed1981

Spinal cord layer I neurons with axon collaterals that generate local arbors.

The morphology an location of physiologically characterized neurons in layer I of the spinal cord dorsal horn were revealed by the intracellular deposition of horseradish peroxidase (HRP). This material showed that the axons of some layer I neurons issue varicosity-bearing collaterals that generate arbors that overlap the neurons' dendritic territories in layer I.

Animals↗
PubMed1980

Physiology and morphology of substantia gelatinosa neurons intracellularly stained with horseradish peroxidase.

Neurons in Rexed's layer II were physiologically characterized with natural and electrical stimuli applied to their cutaneous receptive fields. The neurons were then intracellularly stained with horseradish peroxidase. Three general patterns of physiological responses were found. Nociceptive specific neurons did not respond to gentle mechanical stimulation. Most responded exclusively to tissue-damaging stimuli. Some also responded to moderately heavy pressure, but these responded to noxious stimuli with an increased discharge frequency. Wide dynamic range neurons responded to both gentle mechanical stimulation and to tissue-damaging stimulation. Low-threshold mechanoreceptive neurons responded only to gentle mechanical stimulation. Some of the low-threshold mechanoreceptive neurons were innervated by primary afferents with unmyelinated axons. Excepting those low-threshold mechanoreceptive neurons with input from unmyelinated afferents, the patterns of primary afferents innervation of layer II neurons were similar to the patterns of innervation that have been found for neurons in layers I and IV-V. All but 2 of the 22 neurons that we found were recognized as being of two general morphological types. Stalked cells had their perikarya situated along the superficial border of layer II. Most of their dendrites traveled ventrally while spreading out rostrocaudally. This gave their dendritic arbors a fan-like shape. Stalked cell axons arborized largely in layer I. Islet cell perikarya were found throughout layer II. Most of their dendrites traveled rostrocaudally. Their dendritic arbors were shaped like cylinders with their long axes parallel to the long axis of the spinal cord. Islet cell axons arborized in the immediate vicinity of their dendritic territories, within layer II. Stalked cells and those islet cells whose dendritic arbors were largely contained within the superficial one-third of layer II (layer IIa) were either nociceptive specific or wide dynamic range neurons. The islet cells whose dendritic arbors were largely within the deeper two-thirds of layer II (layer IIb) were all low-threshold mechanoreceptive neurons. These observations suggest that layers IIa and IIb have different functional roles and that stalked cells and islet cells are separate and distinct components of the neural circuitry of the superficial dorsal horn.

Animals↗
PubMed1979

Narcotic analgesia: fentanyl reduces the intensity but not the unpleasantness of painful tooth pulp sensations.

Forty subjects rated the magnitude of painful electrical stimulation of tooth pulp before and after the intravenous administration of either fentanyl, a short-acting narcotic, or a saline placebo. The responses were choices of verbal descriptors from randomized lists of either sensory intensity (that is, weak, mild, intense) or unpleasantness (annoying, unpleasant, distressing) descriptors. The fentanyl significantly reduced the sensory intensity without reducing the unpleasantness of the tooth pulp stimuli, indicating that the mechanisms of narcotic analgesia may include a significant attenuation in pain sensation in addition to effects on pain reaction. These results stress the importance of using multiple measures of pain.

Dental Pulp↗
PubMed1978

The pilo-Ruffini complex: a non-sinus hair and associated slowly-adapting mechanoreceptor in primate facial skin.

A spray-type of nerve ending identified as a Ruffini corpuscle closely associated with a non-sinus hair has been defined in terms of its histologic, ultrastructural and physiologic parameters. The hair and its associated mechanoreceptor, termed a pilo-Ruffini complex, responds as a slowly adapting (SA) mechanoreceptor, whereas most non-sinus hair-associated mechanoreceptors are rapidly adapting. Morphologically, the terminal nerve fibers branch repeatedly within a unique connective tissue matrix, and the neurite and associated connective tissue matrix forms a collar around the hair follicle. This receptor, on the basis of its organization, is interpreted as corresponding to the corpuscle or end organ of Ruffini.

Adaptation, Physiological↗
PubMed1978

New methods of pain measurement and their application to pain control.

Recent pain research advances show promise in their application to the relief of acute and chronic clinical dental pain. Regional electroanalgesia, or transcutaneous electrical stimulation, has been used successfully in the treatment of pain associated with peripheral nerve injuries. Electrical stimulation of teeth also may prove useful as a pain control technique during operative dentistry procedures. Another exciting research finding is the discovery of endogenous or natural pain-suppressing pathways in the brain. There are recent demonstrations that natural-occurring opiate-like compounds and receptors exist in the brain. The elucidation of stimuli and behavioral responses which will activate these specific descending pain control pathways may lead to exciting new methods of pain relief. Thus, both regional electroanalgesia and the discovery of endogenous pain-suppressing pathways offer the possibility of the future expanded use of non-pharmacological pain control techniques. The proper evaluation of new pain control techniques requires the development of better methods of measuring and assessing the multidimensional aspects of the pain experience. Category scales which scale the suprathreshold range of pain from threshold to tolerance levels can be used with both experimental and clinical pain. Sensory Decision Theory has been applied to the analysis of categorical pain responses. This method distinguishes between sensitivity to stimulus intensity and response bias, or the patient's willingness to report a given intensity as painful. Another promising method for scaling pain is the use of ratio-scaling methods with verbal pain descriptors. Verbal descriptors of pain may provide the best method of scaling different dimensions of the pain experience. Reliable and objective descriptor scales have been developed which separate pain along two dimensions: sensory intensity and affect, or unpleasantness. By using cross-modality matching procedures, specific numerical values can be calculated for each verbal descriptor. These scales have been used to measure the intensity and unpleasantness associated with tooth pulp evoked experimental and clinical pain, and should be extremely useful in the evaluation of acute and chronic dental pain. They will be important experimental and clinical adjuncts in determining the efficacy of non-pharmacological pain control methods such as regional electroanalgesia, biofeedback, relaxation-suggestion and hypnosis.

Dental Pulp↗