David Ottoson

Pain alleviation by vibratory stimulation

&NA; In the present study 366 patients suffering acute or chronic musculoskeletal pain of different origin were given vibratory stimulation for the pain. Many of the patients had previously had treatments of various kinds without satisfactory relief. The effect of vibratory stimulation was assessed during and after stimulation using a graphic rating scale. Sixty‐nine per cent of the patients reported a reduction of pain during vibratory stimulation. The best pain reducing site was found to be either the area of pain, the affected muscle or tendon, the antagonistic muscle or a trigger point outside the painful area. In most patients the best pain reducing effect was obtained when the vibratory stimulation was applied with moderate pressure. To obtain a maximal duration of pain relief the stimulation had to be applied for about 25–45 min.

Vibratory stimulation for the relief of pain of dental origin

Abstract The present paper describes the effect of vibratory stimulation on pain of dental origin in 36 patients. The patients were from a clinic for dental surgery and all had suffered pain from pulpal inflammation, apical periodontitis or postoperative pain following extraction of an impacted wisdom tooth for more than 2 days. Vibration at 100 Hz was applied to various points in the facial region or the skull. All the patients except three experienced an effective reduction of the intensity of the pain. In the patients who experienced pain reduction there was usually a best point at which vibration had a greater pain alleviating effect than at other points. At some points the stimulation added to the pain. In 16 patients the stimulation caused a reduction in pain intensity of 75–100%; out of these 12 patients reported a complete relief of pain.

The permeability of the transducer membrane of the crayfish stretch receptor to calcium and other divalent cations.

Abstract The generator potential of the crayfish stretch receptor is produced by the movement of cations through a channel which is opened by stretch. Physiologically, Na + is the main ion moving through the channel; the channel is sufficiently large to admit arginine. The permeability to divalent cations has been measured in solutions in which all of the Na + was replaced by these ions. Ca 2+ , Mg 2+ , Sr 2+ and Ba 2+ were able to move through the channel, as shown by the membrane potential responses to stretch in solutions in which these ions were predominant. Ca 2+ (13.5 min) was found to be necessary in the Ba 2+ and Mg 2+ solutions to maintain membrane integrity; however, in the Sr 2+ solution Ca 2+ was not required. The results of voltage clamp studies showed the resting conductance to decrease in the divalent cation solutions. The reversal potential for the stretch induced current, measured with voltage clamp, was shifted in the negative direction by Ca 2+ , Sr 2+ and Mg 2+ . Two estimates of the value of the ratio of the permeability of Ca 2+ to that of Na + , calculated using the Goldman-Hodgkin-Katz equation, and either the change in reversal potential or the stretch induced current were 1.4 and 0.3 respectively.

Studies on the role of calcium in adaptation of the crustacean stretch receptor. Effects of intracellular injection of calcium, EGTA and TEA

The effects of intracellular pressure injection of Ca2+, EGTA and TEA on the receptor potential of the crayfish stretch receptor were studied. Injection of Ca2+ caused both the transient phase and the static phase of the receptor response to diminish in amplitude, the decrease being greater for the static phase. This phase was almost abolished after a few minutes of injection. Injection of EGTA caused a decrease in the amplitude of the transient phase and an increase of the static phase. These changes progressed during the injection and finally the receptor potential became almost square. After injection of TEA the static phase increased and approached the height of the transient phase making the response almost square. The results provide evidence for the important role of intracellular Ca2+ for the adaptation of the receptor. It is suggested that the adaptive decline of the receptor potential is due to an outward potassium current which is controlled by the intracellular concentration of Ca2+.

Effects of intracellular TEA injection on early adaptation of crustacean stretch receptor

The effects of intracellular injection of TEA on the stretch-induced response of the slowly adapting stretch receptor of the crayfish have been examined to determine the contribution of an outward potassium current to the early adaptation of the neuron. Intracellular recording techniques including potential clamp measurements of membrane currents have been used. Injection of small amounts of TEA caused a pronounced depolarization of the neuron. In the early stage of depolarization there was a marked increase of the static phase of the response while the dynamic phase remained unchanged. When the resting membrane potential was kept constant by current injection both the dynamic phase and the static phase increased. However, the increase of the static phase was more pronounced than that of the dynamic phase and as a result the early phase of adaptation was almost abolished. Following TEA injection the reversal potential for both the dynamic phase and the static phase of the receptor current became somewhat more positive. TEA injection also reduced the outward current induced by a depolarizing potential step. The present results provide additional support for the hypothesis that the early phase of adaptation of the crustacean stretch receptor is attributed mainly to an outward potassium current.

Ionic dependence of early adaptation in the crustacean stretch receptor

In the present study we have examined the effects of changes in potassium and calcium concentration on the early adaptation of the slowly adapting stretch receptor of the crayfish using intracellular recordings including the potential clamp technique. This was because previous studies had suggested that the early adaptative decline of the receptor potential may be attributed mainly to ionic mechanisms involved in the transducer process. During prolonged exposure to K-free saline the cell depolarized; the early adaptive fall of the receptor potential was reduced and finally the response became almost rectangular. These effects developed more rapidly if the concentration of Ca was reduced in the K-free saline. It was shown by injection of current that the effects were not potential dependent. Removal of Ca reduced the amplitude of both the dynamic and static phase of the receptor potential. Isotonic Ca-saline suppressed the static phase of the receptor potential and prolonged exposure completely abolished the response. Potential clamp experiments demonstrated that in the Ca-free saline the passive membrane conductance increased; the static phase of the receptor current increased while the peak current decreased somewhat. In the K-free and Ca-free saline both phases of the receptor current increased. The present results support earlier findings that the major part of the early adaptive fall of the receptor potential is caused by an outward K+ current. Ca2+ modifies the adaptive fall and the static phase, most likely by activation of a Ca2+-dependent K+ current and/or by inactivation of the Na+ current.

Ultrastructural and Electrophysiological Changes in the Olfactory Epithelium following Exposure to Organic Solvents

The present study describes some effects on frog olfactory mucosa following acute exposure to styrene and toluene, two organic solvents. The olfactory summed receptor potential (EOG) was recorded in order to monitor the functional effect. The olfactory epithelium was examined with transmission electron microscopy, using both thin section and freeze-fracture technique. The ultrastructural changes in the olfactory epithelium following exposure to the solvents were mainly of two types: (1) an increased secretion from the sustentacular cells, (2) membrane fusion of the cilia, sometimes with a loosening of the ciliary membrane. The tight junctional complex between the receptor and sustentacular cells at the epithelial surface remained intact. The EOG amplitude generally showed some degree of reduction following exposure, with a gradual recovery towards pre-exposure values.

Pain Treatment by Transcutaneous Electrical Nerve Stimulation (TENS)

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Transcutaneous Electrical Nerve Stimulation

The first modern stimulator for TENS of peripheral nerves for the management of pain was originally developed as a screening device to determine the potential usefulness of surgical implantation of electrodes for the stimulation of the dorsal column of the spinal cord. In these screening tests it became apparent that peripheral stimulation in itself provided excellent pain relief in some patients, and very soon this technique came into widespread use.

Adaptive Properties of Crayfish Stretch Receptor Neurons

It is a common property of many types of receptors that the response to a constant stimulus declines to a more or less steady level which is maintained for the duration of the period of stimulation. Very little is known about the mechanisms underlying this decline. For slowly adapting mechanoreceptors like the muscle spindle adaptation has generally been ascribed to the specific structural properties of the intrafusal fibres by which the stimulus is transmitted to the sensory nerve endings. As was first shown by Katz in 1961 the intrafusal muscle fibres of the frog muscle spindle are almost devoid of myofilaments in the central equatorial region of the spindle. The central zone is therefore probably more elastic than the polar zones of the fibres. This particular arrangement has been assumed to explain the adaptation of the spindle during maintained stretch (cf. Matthews, 1964). Recent observations suggest, however, that only a minor part of the initial adaptive fall of the spindle response can be attributed to mechanical factors, the major part being linked to permeability changes of the transducer membrane during activity (Husmark and Ottoson, 1971 a, 1971 b). These observations raise the question whether or not similar mechanisms may govern the adaptation of other types of slowly adapting mechanoreceptors. The crayfish stretch receptor appeared to offer an ideal preparation for testing this hypothesis. As shown by Florey and Florey (1955) there are two structurally different types of sensory cells in the crayfish (Fig. 1).