Articular Nerve Research Articles

Innervation patterns of the inferior glenohumeral ligament: Anatomical and biomechanical relevance

Although the Inferior Glenohumeral Ligament (IGHL) has a well known mechanical and proprioceptive relevance in shoulder stability, the interrelation of the ligament's anatomical disposition/innervation has not actually been described previously. The purpose of the study was to determine the IGHL innervation patterns and relate them to dislocation. Forty-five embalmed and 16 fresh-frozen human cadaveric shoulders were studied. Masson's Trichrome staining detailed the intraligamentous nerve fiber arrangements. The effect on the articular nerves of an anteroinferior dislocation of the shoulder joint and the position of 60 degrees abduction and 45 degrees external rotation was studied dynamically. The axillary nerve provided IGHL innervation in 95.08% of the cases. We saw two distinct innervation patterns originating from the axillary nerve. In Type 1, one or two collaterals diverged later from the main trunk to enter the ligament. Type 2 showed innervation to the ligament provided by the posterior branch for three to four neural branches. In both cases, these branches enter the ligament near the glenoid rim and at the 7 o'clock position (right shoulder). The radial nerve (Type 3 innervation pattern) provided IGHL innervation in 3.28% of the cases. Microscopic analysis revealed wavy intraligamentous neural branches. The articular branches relaxed and separated from the capsule at the apprehension position and stayed intact after dislocation. These results showed a special predisposition to avoid possible denervation and suggested that the neural arch probably remains unaffected after most dislocations. Knowledge of the neural anatomy of the shoulder will clearly help in avoiding its injury in surgical procedures.

Compression nerveuse par pseudo-kyste mucoïde : à propos de 23 cas: Arguments en faveur de l’origine articulaire

Purpose of the study Mucoid pseudocysts are infrequent benign tumors which can develop on all peripheral nerves near joints. The origin of these cysts remains to be determined. We searched for arguments favoring an articular origin which would have an impact on management and risk of recurrence. Materials and methods Twenty-three patients (21 men and 2 women, mean age 38 years, age range 13-56 years) presented mucoid pseudocysts and were followed for a mean six years. The mucoid pseudocyst was located on the common fibular nerve at the neck of the fibula in 16 patients, on the tibial nerve at the knee in one, on the median nerve in one, on the ulnar nerve in one, and on the suprascapular nerve in two. Pain was local in 18 patients and irradiated to the concerned nerve territory in 20. Motor deficit was the inaugural feature in 17 patients. EMG was performed in all patients, ultrasound exploration in 15, computed tomography in 7 and magnetic resonance imaging in 10. All patients included in this series underwent surgery: pathological diagnosis of mucoid intra-neural pseudocyst was established in all. Systematic search for communication with the neighboring joint was performed in all cases. Results An articular communication was found in 17 patients. Mean time to recovery of muscle force (scored 5) and/or normal sensitivity was seven months in 17 patients. One patient did not achieve full recovery. Three patients experienced recurrence and required tibiofibular arthrodesis. Discussion Three theories have been proposed (cystic degeneration of schwannoma, degeneration of nerve sheath connective tissue, and an articular origin). The articular theory appears to be the most probable. The presence of an articular pedicle in 60% of the patients, the anatomic juxtaposition between the nerves involved and neighboring joints, and occasional migration along the articular nerve as well as the cyst's mucoid content argue in favor of the articular theory. The notion of recurrence after complete minute excision is also in favor of an articular pathogenic mechanism. The diagnosis of mucoid cyst should be retained as a possibility in patients with rapidly progressive signs of nerve compression near a joint. It is important to search for articular communication before and during the surgical excision in order to limit the risk of recurrence.

Differential modulation of primary afferent depolarization of segmental and ascending intraspinal collaterals of single muscle afferents in the cat spinal cord.

We examined primary afferent depolarization (PAD) in the anesthetized cat elicited in 109 pairs of intraspinal collaterals of single group I afferents from the gastrocnemius nerve, one of the pair ending in the L3 segment, around the Clarke's column nuclei, and the other in the L6 segment within the intermediate zone. Tests for refractoriness were made to assess whether the responses produced by intraspinal stimulation in the L3 and L6 segments were due to activation of collaterals of the same afferent fiber. PAD in each collateral was estimated by independent computer-controlled measurement of the intraspinal current required to maintain a constant probability of antidromic firing. In most fibers, stimulation of the ipsilateral posterior biceps and semitendinosus (PBSt) nerve with trains of pulses maximal for group I afferents had a qualitatively similar effect but produced a larger PAD in the L6 than in the L3 collaterals. Stimulation of cutaneous nerves (sural and superficial peroneus) with single pulses and of the posterior articular nerve, the ipsilateral reticular formation, nucleus raphe magnus and contralateral motor cortex with trains of pulses often had qualitatively different effects. They could produce PAD and/or facilitate the PBSt-induced PAD in one collateral, and produce PAH and/or inhibit the PAD in the other collateral. These patterns could be changed in a differential manner by sensory or supraspinal conditioning stimulation. In summary, the present investigation suggests that the segmental and ascending collaterals of individual afferents are not fixed routes for information transmission, but parts of dynamic systems in which information transmitted to segmental reflex pathways and to Clarke's column neurons by common sources can be decoupled by sensory and descending inputs and funneled to specific targets according to the motor tasks to be performed.

Effects of different molecular weight elastoviscous hyaluronan solutions on articular nociceptive afferents

To compare 3 different hyaluronan (HA) preparations used as therapeutic agents for osteoarthritis pain in humans in order to establish the degree to which a single application affects the sensitivity of nociceptors in both the normal and the acutely inflamed rat joint. In anesthetized rats, single-unit recordings were performed from the medial articular nerve of the right knee joint under normal conditions and during an acute experimental arthritis. Fifty fine afferent units (conduction velocities 0.8-15.3 meters/second) responded to passive movements of the knee joint. They were exposed to a torque meter-controlled, standardized stimulus protocol consisting of innocuous and noxious inward and outward rotations of the joint. This stimulus protocol of 50 seconds' duration was repeated every 5 minutes for 2-3 hours. Three commercially available HA preparations and a buffer solution, the solvent of these preparations, were injected intraarticularly after discharges resulting from 6 stimulus protocols were averaged and used as controls. Both in normal and in inflamed joints, the injection of Hyalgan did not reduce nerve impulse frequency of the evoked discharges. The injections of Orthovisc had no effect in normal joints, but produced a transient frequency reduction of the evoked discharge in inflamed joints. Synvisc significantly reduced (by an average of 50%) the impulse discharge in both normal and inflamed joints 50 minutes after injection, and this level of impulse discharge continued until the end of the recording period (120-130 minutes after injection). The buffer, which had elastoviscous properties substantially different from those of Hyalgan, Orthovisc, and Synvisc, had no such effect. We conclude that the elastoviscous properties of HA solutions are determining factors in reducing pain-eliciting nerve activity both in normal and in inflamed rat joints.

Involvement of sympathetic efferents but not capsaicin-sensitive afferents in nociceptin-mediated dual control of rat synovial blood flow.

This study set out to examine the vasomotor effects of the opioid-like peptide nociceptin on knee joint capsular blood flow in urethane-anaesthetized rats. Topical application of nociceptin (10(-15)-10(-8) mol) caused a progressive fall in joint perfusion that was significantly inhibited by the specific nociceptin receptor antagonist [Phe(1)-(CH(2)-NH)-Gly(2)] Nociceptin(1-13)-NH(2) as well as the nonspecific opioid antagonist naloxone. To test whether this constrictor response was sympathetically mediated, we administered nociceptin in animals treated with guanethidine to produce sympathetic blockade or in the presence of the alpha-adrenoceptor antagonist phentolamine. Both guanethidine treatment and phentolamine coadministration attenuated the constrictor response to nociceptin. Inhibition of nociceptin-mediated vasoconstriction revealed a supplementary hyperemic response that persisted in animals whose knee joints were treated with 1% capsaicin to destroy the articular unmyelinated nerve supply. These results show that, in the rat knee, peripheral administration of nociceptin primarily causes a sympathetically mediated vasoconstriction. In addition, high-dose nociceptin produces a vasodilatatory response that is likely due to the direct action of nociceptin on vascular smooth muscle and not by a neurogenic mechanism.

Reflex from the ankle ligaments of the feline

It was found that two to three articular branches of the tibial nerve innervate the medial ligament of the feline ankle. No innervation was found to the laterial ligament. Supramaximal electrical stimulation of the articular nerves was found to elicit electromyographic (EMG) activity in the intrinsic muscles of the foot. EMG activity was not found in any of the calf muscles which cross the ankle. The average time delay from stimulus to EMG activity was 3.8 ms, indicating that a fast, bisynaptic reflex is active, probably for purposes of preventing or correcting foot eversion to maintain joint stability.

Cortical projection of the rat knee joint innervation and its processing in the somatosensory areas SI and SII.

In recent years the rat knee joint has become an important model for the study of nociception of deep tissues. In contrast to the cortical processing of superficial pain, the knowledge about the processing of deep pain evoked by noxious stimuli in tissues such as tendons, bone, and joint is sparse. To obtain a basis for further functional studies, the projections of the knee joint in the cerebral cortex were determined. Cortical surface potentials evoked by electrical stimulation of the posterior articular nerve were recorded by a platinum ball electrode. Evoked activity was found in the primary somatosensory area SI in an area of about 3 x 3 mm on the contralateral side. Its center was located about 3 mm caudal to the bregma and about 3 mm lateral to the superior sagittal sinus. A small projection in SII was found on the lateral side of the cortex about 6 mm lateral from SI. This area had a size of about 1 x 1 mm, and the amplitudes of the potentials were smaller but had similar latencies to those in SI. An additional projection with small potentials and longer latencies was observed in SI on the ipsilateral side. Cooling of the contralateral SI revealed deprivation of the ipsilateral evoked potentials in SI whereas the potentials in SII remained unchanged. These data indicate that information from the knee joint is processed in parallel in SI and SII on the contralateral side and that there is an additional serial processing in SI on the ipsilateral side.

Sensitisation of group III articular afferents to mechanical stimuli by substance P.

To examine the excitatory and sensitising effects of substance P (SP) on articular afferents in normal and acutely inflamed cat knee joints. In anesthetised cats recordings were made from 15 group III (conduction velocity 2.5-20 m/s) and 25 group IV afferent units (conduction velocity < 2.5 m/s) of the medial articular nerve of normal and acutely inflamed knee joints. SP (10 and 100 microg) was administered close-arterially. SP at doses of 10 microg and 100 microg activated less than 50% of both group III and group IV units. The proportion of SP-positive units was significantly higher in inflamed (10 of 21) than in normal joints (2 of 18). SP induced activity in initially silent units or increased ongoing activity after latencies varying from 2 s to 5 min. The SP-evoked activity had an irregular pattern, a variable duration, and was not related to the dose injected. Bolus injections of SP (100 microg) sensitised group III articular afferents but not group IV units to noxious movements of the joint, regardless whether the units were from normal or acutely inflamed joints. The responses to innocuous movements were not influenced by SP. Group III units, initially not activated by any movement, displayed vigorous discharges to noxious movements after close-arterial SP. In 3 group III units tested, the SP-induced augmentation of responses to noxious movements was not mimicked by close-arterial injection of histamine (3.3 microg). It is concluded that SP contributes to the sensitisation of a subpopulation of high-threshold articular afferents. Thus this neuronal mediator released peripherally in response to an injury or acute inflammation causes considerable changes in the mechanosensitivity of this subpopulation of nociceptive joint afferents.

Composition of the medial and posterior articular nerves of the mouse knee joint

The number and the distribution of fiber size in the medial (MAN) and posterior (PAN) articular nerves of the mouse knee joint were studied by electron microscopy. The MAN contained 75 - 28 nerve fibers consisting of 63 - 24 unmyelinated and 12 - 6 myelinated fibers. The PAN was composed of 195 - 50 nerve fibers, namely 129 - 28 unmyelinated and 66 - 24 myelinated fibers. A skewed unimodal distribution of the unmyelinated nerve fiber diameters was seen in both nerves ranging from 0.1 to 1.2 w m with a maximum between 0.3 and 0.6 w m. The myelinated nerve fibers in the MAN ranged from 1 to 8 w m with a peak between 2 and 5 w m. In the PAN, their diameters ranged from 1 to 12 w m with a clearly visible peak at 4-5 w m and a plateau at 8-9 w m that may represent a second maximum. These data show that the knee joint innervation of the mouse is comparable to those of the cat and rat concerning the types of nerve fibers and the composition of the two nerves. However, in relation to the much smaller area of tissue to be innervated the total number of primary afferents is considerable smaller in the mouse.

Normal and pathological adaptations of articular cartilage to joint loading.

Joints are functional units that transmit mechanical loads between contacting bones during normal daily or specialized activities, e.g., sports. All components of the joint, i.e. articular cartilage, bone, muscles, ligaments/tendons and nerves, participate in load transmission. Failure in any of these components can cause joint malfunction, which, in turn, may lead to accumulation of damage in other joint components. Mechanical forces have great influence on the synthesis and rate of turnover of articular cartilage molecules, such as proteoglycans (PGs). Regular cyclic loading of the joint enhances PG synthesis and makes cartilage stiff. On the other hand, loading appears to have less evident effects on the articular cartilage collagen fibril network. Continuous compression of the cartilage diminishes PG synthesis and causes damage of the tissue through necrosis. The prevailing view is that osteoarthrosis (OA) starts from the cartilage surface through PG depletion and fibrillation of the superficial collagen network. It has also been suggested that the initial structural changes take place in the subchondral bone, especially when the joint is exposed to an impact type of loading. This in turn would create an altered stress pattern on joint surfaces, which leads to structural damage and mechanical failure of articular cartilage. The importance of the neuromuscular system to the initiation and progression of OA is still poorly understood. Many surgical extra- and intra-articular procedures have been used for the treatment of OA. Although some of the new methods, such as autologous chondrocyte transplantation and mosaicplasty, have given good clinical results, it is reasonable to emphasize that the methods still are experimental and more controlled studies are needed.

Alteration in α‐ and β‐Adrenoceptor Profile of Rabbit Knee Joint Blood Vessels due to Acute Inflammation

Experiments were performed to investigate the nature of - and -adrenoceptors in blood vessels supplying the posterior capsule of the acutely inflamed rabbit knee joint, and results were compared to findings from previous experiments on the normal joint, to assess any alteration which may occur in the adrenoceptor profile due to the inflammation process. Electrical stimulation of the posterior articular nerve resulted in vasoconstriction which was reversed to vasodilatation by phentolamine and yohimbine. The dose-response curves to close intra-arterial injection of -adrenoceptor agonists showed a rank-order potency of: adrenaline = phenylephrine = clonidine. The adrenaline dose-response curve was shifted to the right by administration of antagonists with a rank-order potency of: phentolamine = yohimbine = prazosin. At this stage of the experiments there was an equal response of 1- and 2-adrenoceptors in blood vessels of the acutely inflamed rabbit knee joint. In another group of animals the neurally mediated vasodilatation, which appeared after administration of phentolamine, was completely blocked by propranolol, and was reduced by about 50 % by atenolol. The dose-response curves to close intra-arterial injection of -adrenoceptor agonists showed a rank-order potency of: isoprenaline > salbutamol = dobutamine. The isoprenaline dose-response curve was shifted to the right by administration of antagonists with a rank-order potency of: propranolol > atenolol. These experiments also showed an almost equal response of 1- and 2-adrenoceptors in blood vessels of the acutely inflamed rabbit knee joint. Overall, compared to previous experiments on the normal joint in which 2- and 1-adrenoceptor responses predominated, acute inflammation resulted in a shift from 2- towards 1- and from 1- towards 2-adrenoceptor responses.

Innervation of the metacarpophalangeal and interphalangeal joints: a microanatomic and histologic study of the nerve endings.

Six pairs of fresh human cadaver hands were dissected under the surgical microscope at x28 to x32 and selectively silver stained. In addition, 18 proximal interphalangeal and metacarpophalangeal joints of fresh cadaver hands were processed with protein gene product 9.5 for measurement and analysis of nerve endings in those joints. The results demonstrated that the proximal interphalangeal joints are innervated by 2 palmar articular nerves (mean diameter, 0.21-0.53 mm). Each metacarpophalangeal joint of the second through fifth fingers is predominantly supplied by 1 palmar articular nerve (mean diameter, 0.41-0.59 mm), which comes from the deep branches of the ulnar nerve, as well as by 2 dorsal articular nerves (mean diameter, 0.11-0.24 mm). The metacarpophalangeal joint of the thumb also had 2 dorsal articular nerves (mean diameter, 0.18-0.24 mm) and 2 palmar joint nerves (mean diameter, 0.29-0.31 mm). The mean densities of the type IV free nerve endings and the mean numbers of the encapsulated endings in the palmar capsules were consistently much greater than in the dorsal or lateral capsules. The majority of encapsulated endings were pacinian corpuscles. The anatomic and histologic information may help the surgeon avoid damaging these small joint nerves during operative procedures and to reconstruct or de-innervate them if necessary. (J Hand Surg 2000; 25A:128-133.

The role of type 1 metabotropic glutamate receptors in the generation of dorsal root reflexes induced by acute arthritis or the spinal infusion of 4-aminopyridine in the anesthetized rat

Antidromically propagated action potentials can be recorded in the proximal end of the severed medial articular nerve (MAN) on mechanical stimulation of an inflamed knee in rats and are referred to as dorsal root reflex (DRR) activity. The absence of DRR activity in normal rats suggests that the activity could be the result of hyperexcitability of spinal neurons induced by inflammation. In this study, the role of spinal type 1 metabotropic glutamate (mGlu1) receptors in the generation of DRR activity in the MAN during acute knee inflammation was investigated. Four hours after an injection of a mixture of kaolin and carrageenan (k/c) into a knee joint, DRR activity could be evoked in the ipsilateral MAN by mechanical stimulation of the inflamed limb. Spinal application of a selective mGllu1) receptor antagonist, [RS]-1-Aminoindan-1,5-dicarboxylic acid/UPF 523 (AIDA), or a potent, but less specific mGlu1 receptor antagonist, LY393053, both depressed the DRR activity significantly. AIDA and LY39053 had no effect on recordings in the MAN from noninflamed control animals. However, spinal administration of AIDA did suppress DRR activity generated by infusion of 4-aminopyridine (4-AP), a K+ channel blocker, into the dorsal horn of noninflamed animals. These observations suggest that (mGlu1) receptors support the generation of DRR activity in the MAN following sensitization of spinal cord neurons.

Neurogenic origin of articular hyperemia in early degenerative joint disease.

It has been speculated that joint instability resulting from anterior cruciate ligament (ACL) rupture could be exacerbated by changes in vasomotor activity in the remaining supporting structures. In this study, the effect of ACL transection on medial collateral ligament (MCL) basal perfusion and its responsiveness to calcitonin gene-related peptide (CGRP) and sympathetic adrenergic influences was examined. Using urethan-anesthetized rabbits, we tested the effects of CGRP and its antagonist CGRP-(8-37) by topical application of these agents to the exposed knee while sympathetic influences were tested by electrically stimulating the saphenous nerve. It was found that MCL basal perfusion was elevated in ACL-sectioned joints; however, this effect was abrogated by prior resection of the articular nerve supply. At the doses tested, the normal vasodilator response to CGRP was abolished in ACL-sectioned joints, whereas the response to CGRP-(8-37) was attenuated. Even under the influence of increased constrictor tone, MCL and capsule blood vessels still showed substantially reduced responses to exogenous CGRP administration. By contrast, nerve-mediated constrictor responses were mostly unaffected by joint instability. This study suggests that posttraumatic knee joint hyperemia is neurogenically mediated, possibly by increased secretion of CGRP.

Anterior cruciate ligament reconstruction affects proprioception in the cat's knee.

To study the cat's knee after anterior cruciate ligament reconstruction, we compared its neural and muscular activity with that in the normal and the unstable knee. We recorded the electric activity in the articular nerves (posterior -PAN and medial -MAN) and periarticular muscles (quadriceps and hamstring) while performing passive flexion, extension, external and internal rotation, and also anterior translation of the tibia at 30 degrees and 90 degrees of flexion. The same series of maneuvers was performed in the same knees after surgical section of the anterior cruciate ligament and then after anterior cruciate reconstruction. The electric activity recorded in the reconstructed knee was compared to that in the same knee before surgery and in the same unstable knee after anterior cruciate section. We observed that the reconstructed knee, compared to the injured knee, showed a decrease in articular nerves and quadriceps activity while it regained stability. This decrease converged to the recordings in the normal knee. However, differences in MAN, PAN and hamstring activity were still present in the reconstructed knee. This suggests that, although anterior cruciate reconstruction seems beneficial for restoring articular nerve and periarticular muscle activities to a certain degree, proprioception in the reconstructed knee does not match that in the normal knee.

Sensory afferent properties of immobilised or inflamed rat knees during continuous passive movement

We studied the sensory afferent properties of normal, immobilised and inflamed rat knees by recording the activity of the medial articular nerve (MAN). When the knee was inflamed by kaolin-carrageenan or immobilised for six weeks, MAN activity significantly increased during rest and continuous passive motion (CPM). The maximal discharge rate tended to increase depending on the angular velocity of the CPM. When the knees were then rested for one hour before again starting CPM, activity was further increased at the initial CPM cycle, the ‘post-rest effect’. Analysis of the conduction velocity showed that 94% and 66% of spike units on the recorded discharge of the immobilised and inflamed knees, respectively, belonged to fine nerve fibres. Our findings show that the sensory receptors in the knee are sensitised in a similar manner by immobilisation and by inflammation, suggesting a relationship to pain. The post-rest effect may be related to a characteristic symptom of osteoarthritis called ‘starting pain’.

Sensory afferent properties of immobilised or inflamed rat knees during continuous passive movement

We studied the sensory afferent properties of normal, immobilised and inflamed rat knees by recording the activity of the medial articular nerve (MAN). When the knee was inflamed by kaolin-carrageenan or immobilised for six weeks, MAN activity significantly increased during rest and continuous passive motion (CPM). The maximal discharge rate tended to increase depending on the angular velocity of the CPM. When the knees were then rested for one hour before again starting CPM, activity was further increased at the initial CPM cycle, the 'post-rest effect'. Analysis of the conduction velocity showed that 94% and 66% of spike units on the recorded discharge of the immobilised and inflamed knees, respectively, belonged to fine nerve fibres. Our findings show that the sensory receptors in the knee are sensitised in a similar manner by immobilisation and by inflammation, suggesting a relationship to pain. The post-rest effect may be related to a characteristic symptom of osteoarthritis called 'starting pain'.

P2X receptor-mediated excitation of nociceptive afferents in the normal and arthritic rat knee joint.

1. We tested the hypothesis that functional P2X receptors are present on peripheral terminals of primary afferent articular nociceptors in the rat knee joint. Neural activity was recorded extracellularly from the medial articular nerve innervating the knee joint in rats anaesthetized with pentobarbitone. 2. The selective P2X receptor agonist, alphabeta methylene ATP (alphabetameATP), and the endogenous ligand, ATP, caused a rapid short-lasting excitation of a sub-population of C and Adelta nociceptive afferent nerves innervating normal knee joints when injected intra-arterially or intra-articularly, and this effect was antagonized by the non-selective P2 receptor antagonist PPADS. 3. Induction of a chronic (14-21 days) unilateral inflammatory arthritis of the knee joint using locally injected Freund's adjuvant neither increased or decreased responsiveness of joint nociceptors to alphabetameATP or ATP. 4. Our results support the hypothesis that alphabetameATP-sensitive P2X receptors are expressed on peripheral nociceptive afferents in the rat knee joint suggesting that they may be involved in the initiation of nociception and pain.

Surgical results after soft system stabilization of the lumbar spine in degenerative disc disease--long-term results.

After having reported preliminary results of soft system stabilization according to Graf in a series of 27 patients with degenerative disc disease of the lumbar spine in early 1995 the authors report long term clinical and radiological results of this patient series (n = 25). At a mean period of postoperative observation of 50 months excellent, good, satisfactory, moderate and poor results were obtained in 62, 9%, 11, 1% and 11, 1%, 7, 4% and 7, 4% of the patients, respectively. The well-known phenomenon of loss of disc height at the level of posterolateral fusion and instrumentation as well as overcharge of adjacent segments were not observed after soft system stabilization. Regional as well as global lumbar lordosis were maintained and, although statistically not significant, an increase of intervertebral distance was observed in adjacent segments in flexion of the lumbar spine. These phenomena might represent pressurization of instrumented as well as adjacent discs after the insertion of ligament prostheses. It is the impression of the authors, that the Graf technique leads to good surgical results in degenerative disc disease with destabilization of lumbar motion segment(s) if the following criteria are strictly respected: 1. No or only mild arthrotic changes of the facet joints 2. Preferably minor disc degeneration/only mild loss of intervertebral distance. 3. Well trained low back muscles and 4. A clear-cut, repeatedly demonstrated pain-relief on trial anaesthesia of the corresponding articular nerves and while wearing a probatory jacket.

An intact peripheral nerve preparation for examining the central actions of single kinaesthetic afferent fibres arising in the wrist joint of the cat

Intraneural microstimulation of single tactile or kinaesthetic afferent fibres arising in the hand of conscious human subjects has revealed marked differences among the different classes in their capacity to generate a perceptual response. In order to test the hypothesis that these different capacities might reflect a differential security in the transmission of singnals across synaptic junctions in the dorsal column nuclei or other levels of the somatosensory pathway we have previously developed a paired, simultaneous recording paradigm in the cat to analyze transmission characteristics within the dorsal column nuclei for single identified tactile and muscle sensory fibres of the forearm. These studies have depended upon the use of a fine peripheral nerve or nerve fascicle preparation in which it is possible to monitor the activity of single sensory fibres while the nerve remains in continuity with the central nervous system. Although we have previously described a preparation that allows the activity of single joint afferent fibres from the hindlimb to be monitored in the intact medial articular nerve, these hindlimb kinaesthetic afferents fail to project directly to the dorsal column nuclei. In the present study we report a forearm nerve preparation in the cat that permits the simultaneous recording of activity from individual wrist joint afferent fibres and their target neurones of the dorsal column nuclei. When this nerve is freed from nearby tissue over a distance of 2-4 cm and left in continuity, it is possible with a silver hook electrode to monitor the impulse activity of each group II joint afferent fibre with an excellent signal-to-noise ratio. The preparation should prove ideal for examining the central actions and security of transmission across the dorsal column nuclei for single, identified joint afferent fibres of the forearm.