This study focuses on the influence of trait anxiety and mood variables on changes in tooth pain threshold following two similar methods of somatic afferent stimulation, one familiar (manual acupuncture) and one unfamiliar (low-frequency transcutaneous electrical nerve stimulation [low-TENS]). Twenty-one acupuncture responders, treated for long-lasting orofacial muscular pain but naive to low-TENS, were selected for the study. In an experimental session, acupuncture and low-TENS were randomly given during two periods separated by a rest interval. Tooth pain thresholds (PT) were measured before and after stimulation with a computerized electrical pulp tester. Trait anxiety and depression were assessed with psychometric forms before the experimental session in all patients, whereas momentary mood was assessed in 10 randomly selected patients with visual analogue scales during and after the two types of stimulation. Following acupuncture, the group average PT increased significantly, whereas no significant change was observed following low-TENS. Higher scores on trait anxiety correlated significantly with a low PT increase following low-TENS, and higher ratings of stress correlated significantly with a low PT increase following acupuncture. This indicates that the magnitude of analgesia induced by these methods may be modified by psychologic factors like anxiety and stress.

The purposes of the present study were to describe physical and psychological characteristics of 55 chronic pain patients with predominantly nociceptive neck and shoulder complaints, and to explore relationships between physical assessment methods, self-reported pain and psychological distress. The physical measures included cervical and shoulder mobility and muscle tenderness. The Pain Severity and Interference subscales from the Multidimensional Pain Inventory (MPI), Becks Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI-Y), and a pain drawing assessed self-reports of pain and psychological distress. The number of tender points (TP score) correlated significantly with pain severity, (p < 0.01) Interference (p < 0.05), pain drawing score (p < 0.05), BDI (p < 0.05) and state anxiety (p < 0.05). No significant correlation was seen between TP score and age, pain duration or trait anxiety. The results suggest that there are relationships between observers' ratings of muscle tenderness (TP score) and self-reports of pain severity, interference of pain and psychological distress in patients with chronic cervico-brachial pain.

Changes in skin temperature and haemodynamics were studied during experimentally administered electro-acupuncture before and after a 4-week period of electro-acupuncture (EA) treatments. Subjective pain intensity was evaluated using a pain questionnaire. Twelve patients with long-lasting nociceptive pain were included. Before clinical treatment, skin temperature tended to decrease after 30 minutes' stimulation. In contrast, a significant increase was seen after the clinical treatment. No significant changes were seen for blood pressure, heart rate or pain intensity before and after the clinical treatment. The data indicate that an increased skin vasoconstrictor sympathetic activity may be responsible for the decreased skin temperature during the electro-acupuncture in the initial test sessions, whereas an inhibition of skin sympathetic activity and/or a release of vasodilatory substances may be responsible for the increase in temperature after completed clinical treatment. Despite a small number of subjects and correction for multiple inference, the difference in temperature effects before and up to 3 months after acupuncture treatment was significant.

In order to assess whether electro-acupuncture (EA) can reduce a high uterine artery blood flow impedance, 10 infertile but otherwise healthy women with a pulsatility index (PI) >=3.0 in the uterine arteries were treated with EA in a prospective, non-randomized study. Before inclusion in the study and throughout the entire study period, the women were down-regulated with a gonadotrophin-releasing hormone analogue (GnRHa) in order to exclude any fluctuating endogenous hormone effects on the PI. The baseline PI was measured when the serum oestradiol was <=0.1 nmol/l, and thereafter the women were given EA eight times, twice a week for 4 weeks. The PI was measured again closely after the eighth EA treatment, and once more 10-14 days after the EA period. Skin temperature on the forehead (STFH) and in the lumbrosacral area (STLS) was measured during the first, fifth and eighth EA treatments. Compared to the mean baseline PI, the mean PI was significantly reduced both shortly after the eighth EA treatment (P < 0.0001) and 10-14 days after the EA period (P < 0.0001). STFH increased significantly during the EA treatments. It is suggested that both of these effects are due to a central inhibition of the sympathetic activity.

The present study was performed on 20 patients randomly selected from a large group with noise-induced tinnitus in order to investigate the effect of acupuncture on their tinnitus. The patients were divided into two groups. One group first received classical Chinese needle acupuncture for 5 weeks, and the other was given a placebo procedure; after a 2-week interval, the procedures were reversed. A single-blind cross-over design was used. Acupuncture was given by a Chinese otolaryngologist around the ear as well as at distal points on the extremities. Placebo consisted of mock electrical stimulation via surface electrodes connected to a Chinese electro-acupuncture stimulator which delivered a weak sound and a light flash at a frequency of 2 Hz but no current to the surface electrodes. The effect was evaluated by the use of visual analogue scales. No significant difference between acupuncture and placebo was found in annoyance, awareness or loudness of the tinnitus. Many patients indicated a preference for acupuncture due to unspecific effects such as improved sleep, decreased muscle tension and improved blood circulation. It is concluded that acupuncture has no specific alleviating effect on noise-induced tinnitus.

The present study investigates the relationships between clinical pain relief, physiological and psychological parameters. Out of 50 patients with long-lasting musculoskeletal neck- and shoulder-pain treated with transcutaneous electrical nerve stimulation (TENS), 21 were selected and classified as responders (n = 13) or non-responders (n = 8). Tooth pain thresholds (PT) were measured before and after an experimental TENS treatment and the relative change in PT following the stimulation was calculated. Three psychometric self-inventories were administered: Zung Depression Scale, Spielberger's Trait Anxiety Scale and the Multidimensional Health Locus of Control Scale. Responders (R) and non-responders (NR) differed significantly from each other in the PT measurements as well as on the psychometric scales. NR exhibited higher levels of anxiety and depression, a more pronounced powerful other orientation and no change or a decrease in PT following TENS compared to R. These findings indicate relationships and interactions between physiological and psychological factors in patients with long-lasting pain.

The non-myelinated axons in peripheral nerves were originally reported in 1838 by Remak, although their detailed description had to await the introduction of the electron microscope. Most of them are dorsal root afferent, but some enter the spinal cord via the ventral roots. Their functional characteristics, and particularly the role in pain attracted attention in the 1930′s. The introduction in 1956 of single unit C-fibre recording yielded exact information needed for a satisfactory analysis of the receptor characteristics. A broad survey is made of C-fibre afferents in the viscera, skin and deeper somatic tissues. The action of these C-fibres in the central nervous system, principally in the dorsal horn of the spinal cord is briefly reviewed.

Non-myelinated C-fibre responses during sympathetic trunk stimulation were studied in rabbit common peroneal nerve 2 weeks after the nerve had been subjected to compression at 400 mmHg for 30 min. Our previous studies have demonstrated that during sympathetic trunk stimulation the compound action potential of uninjured somatic C-fibres is characterized by a reduced amplitude and an increased latency. In the present study, nerve compression changed the C-fibre response to sympathetic stimulation. Three out of eight nerves reacted to nerve compression by increased C-fibre compound action potential amplitude in response to sympathetic stimulation. In three other rabbits with compressed nerves the C-fibre action potential amplitude was unchanged, and in the remaining two rabbits the action potential amplitude was decreased during sympathetic stimulation. The action potential latency increased in all tested compressed C-fibres. The phenomenon of increased C-fibre amplitude during sympathetic activation has not been observed in uninjured nerves. As in uninjured nerves, noradrenaline infusion produced an increased C-fibre action potential amplitude and latency in six animals. Sympathetic stimulation did not affect the A-fibre response. These results indicate that sympathetic activity influences the conduction properties in C-fibres of somatic origin and that the response can be changed after a nerve injury. The findings may be of importance for the understanding of pain aggravation in different types of nerve injuries during increased sympathetic activity.

Single afferent unmyelinated fibres were dissected from the otherwise intact sural nerve in anesthetized rabbits. The sympathetic trunk could be stimulated via electrodes implanted through the abdomen. The response in single C fibres was elicited by electrical stimulation in the cutaneous innervation area of the fibre. Sympathetic stimulation (8 Hz, 1 ms pulses, 5 mA for 60 s) increased the latency in all tested C fibres (2.0% +/- 0.8%, mean +/- SD, n = 17). In 48% of the units the amplitude of the action potential decreased (26.4% +/- 12.3%) during sympathetic stimulation. Infusion of noradrenaline (5 micrograms min-1) increased (7.7% +/- 4.1%) the latency in all units and increased (36.9% +/- 29.8%) the amplitude of 25% of the units. The effects of sympathetic stimulation and noradrenaline infusion were blocked by pre-treatment with phentolamine (3 mg kg-1 i.v.). The results suggest that catecholamines change the membrane properties of unmyelinated fibres.

Unmyelinated C-fibre responses to electrical stimulation were recorded in common peroneal, sural and tibial nerves of rabbits. Three distinct C elevations, here called C1, C2 and C3, were recorded. C2 is probably of somatic origin because it was depressed due to collision by peripheral stimulation of cutaneous receptors. The conduction velocity of C3 corresponded to that of sympathetic post-ganglionic fibres. During sympathetic trunk stimulation the A-fibre responses were not significantly changed while C responses, especially C2, were reduced in amplitude and slightly delayed. The C-fibre responses were also influenced by intra-arterial infusion of noradrenaline. In most cases, the latency of the response was increased. The effect of sympathetic stimulation was completely blocked by hexamethonium, and partly blocked by phentolamine, an adrenergic alpha-receptor blocking agent which also blocked the effect of noradrenaline. The findings suggest that there are adrenergic receptors distributed along unmyelinated somatic afferent fibres. Sympathetic activity may release noradrenaline in the peripheral nerve, resulting in changed conductive properties in unmyelinated fibres transmitting sensory information.

Compound action potentials of both myelinated (A) and non‐myelinated (C) fibres in the common peroneal nerve of rabbits were studied during and after acute, graded compression of the nerve at 200 or 400 mmHg applied for 2 h or during ischaemia created by nitrogen inhalation or aortic occlusion. Compression of the nerve at 200 mmHg blocked the Ai component (large myelinated fibres) after about 23 min, while compression at 400 mmHg shortened this time to 11 min. The A2 component (thinner myelinated fibres) had a lower conduction velocity and a higher resistance to compression. There was just a slight decrease in conduction velocity of the nonmyelinated fibres when the nerves were compressed at 200 mmHg for 2 h. However, compression at 400 mmHg for 2 h induced a marked deterioration of amplitude and conduction velocity of the C‐fibres. There was an incomplete restitution of function of A‐ and C‐fibres during 2 h of recovery. The thinner myelinated fibres were more susceptible to deprivation of oxygen than the thicker ones, while non‐myelinated fibres differed in response according to method of ischaemia induction. It is concluded that non‐myelinated fibres are very resistant to compression and a very high pressure (> 400 mmHg) is needed to affect these fibres.

Functional development of the visual system in normal and protein deprived rats. V. Specific cortical response and repetitive stimulation in adult rats. Acta Physiol Scand130, 705–711. Received 29 December 1986, accepted 16 March 1987. ISSN 0001–6771. Departments of Physiology and Pathology, University of Göteborg, Sweden.Recent studies on the specific visual system have indicated that early induced protein deprivation results in an impaired transmission from cell to cell in the cortex. To further investigate cortical mechanisms the response to repetitive light flashes and to electrical stimulation of the optic tract (OT) and the dorsal lateral geniculate nucleus (dLGN) were examined. The first potential of the surface visual evoked response (VER) and the monosynaptic response to OT and dLGN stimulation showed similar sensitivity to repetitive stimulation in C and PD rats. In PD rats later activity was significantly more sensitive to repetitive stimulation than in controls. By using paired stimuli with a short inter‐stimulus interval, similar inhibitory mechanisms in PD and C rats were demonstrated. The results support the view that protein deprivation results in impaired cortical synaptic activation. The results are discussed in relation to previously described impairment at the cortical level in malnourished animals.

It was recently shown that an increase in latency of the cortical visual evoked response (VER) seen in young malnourished animals persists in adult rats given a low protein diet. In the present paper the VER latencies of the specific visual pathway were measured in order to establish the level at which the latency increase occurs in protein-deprived rats. The VER in the dorsal lateral geniculate nucleus (dLGN) showed no significant differences to onset or peak latencies between control (C) and the protein-deprived (PD) rats. The dLGN activity was higher in C rats than in PD rats. Late components differed in median values between the two groups, but the individual variations were large. Generally, the VER of the dLGN in PD rats was more stereotype compared with the C rats. Intracortical VER at a depth of 0.4-0.5 mm showed a small negative component of short onset latency in both C and PD rats. This component preceded the onset of the initial positivity recorded from the cortical surface by 1-2 ms in C rats and by 3-6 ms in PD rats. Following electrical stimulation of the dLGN, no differences in onset latency of the first cortical activity (monosynaptic response) were recorded between C and PD rats, whereas later activity was significantly delayed in PD compared with C rats. The laminar potential pattern was less distinct in PD compared with C rats, and the late components of the evoked response from deep cortical layers were markedly attenuated or lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Previous studies have shown that muscle exercise and low frequency transcutaneous nerve stimulation (TNS) give rise to an analgesic effect in humans and animals. Endorphin has been proposed to mediate this analgesia. In this investigation, the effect of muscle exercise and low frequency TNS, on dental pain thresholds was studied and the possible involvement of endorphinergic mechanisms was investigated using naloxone as an antagonist. Dental pain thresholds were measured in 11 volunteers following leg or arm exercise and after low frequency TNS of the hands or face. After exercise (20 min) or stimulation (30 min) either 0.8 mg naloxone (2 ml) or saline (2 ml) was injected i.v. in a double-blind fashion. Pain thresholds were measured repetitively before and after exercise or stimulation. Both leg and arm exercise increased pain threshold. Stimulation of the hands also increased pain threshold, but less than arm exercise. A marked increase in pain threshold was seen after face stimulation. These changes in pain threshold were unaffected following injections of either naloxone or saline, except for an early and short-lasting reduction when naloxone was injected following arm exercise. The increases in pain threshold following muscle exercise and after low frequency TNS, showed similarities suggesting that a common mechanism might be involved. The pain threshold increase after arm exercise could only be partially mediated by endorphinergic mechanisms.

Morphological studies have indicated that proximal nerve ends of transected rat sciatic nerves regenerating into preformed mesothelial chambers show a different organization as compared to neuromas developed in contact with a muscle fascia. We have studied the physiological properties of nerve fibres arising from these types of preparations with reference to ongoing activity, response to mechanical stimulation and noradrenaline sensitivity. The study included also fibres arising from ligated and encapsulated neuromas. Fibres with ongoing activity arising from the neuroma could be found from neuromas in contact with a muscle fascia and also from ligated and encapsulated neuromas. This ongoing activity was enhanced by mechanical stimulation and i.v. infusion of noradrenaline. In contrast, fibres arising from proximal nerve ends in mesothelial chambers did not show ongoing activity. These silent fibres responded dynamically to light mechanical stimulation. Noradrenaline did not induce ongoing activity in these fibres.

Gastric motor responses, recorded as volume changes of an intragastric balloon, were induced by the close i.a. administration of bradykinin (0.75-4 micrograms) in chloralose-anaesthetized cats. The animals were vagotomized and the adrenals were ligated at the outset of the experiments. Prior to autonomic blocking agents bradykinin elicited relaxatory or biphasic motor responses. Following nicotinic ganglionic receptor blockade bradykinin caused predominantly gastric contractions. Such excitatory responses were antagonized by 80-100% by atropine, suggesting a dominant neurogenic component. An hypothesis is put forward that the observed gastric contractions result from a bradykinin-induced activation of an axon reflex arrangement confined to thin sensory nerve fibres which, by substance P release from intramural collaterals, excite postganglionic cholinergic motor neurones.

The importance of the temperature of the dentine was studied in teeth prepared for electrical stimulation. During experiments with the mouth open, the temperature of teeth covered by cement was normal. The digastric EMG and the brainstem — evoked response following electrical stimulation of the tooth pulp as well as the threshold for eliciting a jaw-opening response remained constant throughout prolonged experiments. However, heat produced by the cement used to fixate the tooth electrodes could have damaged the tooth if the dentine temperature had exceeded 45°C. A careful preparation of the tooth pulp by repeated application of thin layers of cement allowed an adequate preparation without damage to tooth pulp afferents.

There is evidence that the cerebral cortex is involved in the perception of pain but no specific area appears to be the ‘pain centre’. Limited knowledge exists on the cortical processing of the noxious input. The nociceptors are most likely to activate at least two different systems with different characteristics. One has a bilateral cortical projection, no apparent topographical pattern, low synaptic security and excites cells in large areas. This system may give rise to the widespread increase in blood flow and the widely distributed surface potentials recorded in man following a painful stimulus. Noxious stimuli also excite a system with contralateral topographical projection, high synaptic security and termination in lamina IV. This system produces EPSP-IPSP sequences in cells in a restricted cortical area. Pronounced inhibition of cells in lamina IV and more superficial layers is induced by activity in low threshold afferents. Thus, similarly as at the segmental spinal level, the nociceptive input to cortical cells is processed and integrated with the activity in other afferent systems.