Search Results - (Author, Cooperation:R. F. Schmidt)

2016-03-12

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Aged ; Amino Acid Substitution ; Animals ; Cholesterol, HDL/*blood ; Coronary Disease/*blood/*genetics ; DNA Mutational Analysis ; Female ; Genetic Variation ; Heterozygote ; Homozygote ; Humans ; Leucine/genetics ; Male ; Mice ; Middle Aged ; Proline/genetics ; Protein Processing, Post-Translational ; Risk ; Scavenger Receptors, Class B/*genetics/metabolism

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The central organization and the functional significance of the powerful presynaptic inhibition of cutaneous afferent fibres2 cannot be examined in detail by using electrical stimulation of peripheral nerves, since neither is there a correlation between the nerve fibre threshold and the various ...

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1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] IN the pathway from cutaneous nerves to the sensory cortex a conditioning volley is followed by a deep and prolonged (about 150 msec.) depression of the primary cortical response evoked by a testing volley in the same nerve or in another nerve of that limb1-4. Much of the depression has been shown ...

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1432-1106

Unanesthetized cat ; Cerebellum ; Mossy fiber input ; Climbing fiber input ; Cutaneous mechanoreceptors

Springer Online Journal Archives 1860-2000

Medicine

Summary 1. Mossy and climbing fiber inputs from cutaneous mechanoreceptors to Purkyně cells of vermis and pars intermedia of the cerebellar anterior lobe were studied in locally anesthetized, paralyzed cats prepared for painless recording sessions. In this preparation the mossy fiber and climbing fiber pathways remain fully functional. Simple spikes and climbing fiber discharges were recorded simultaneously through extracellular glass micro-electrodes and thereafter filtered off from each other for separate, computer-assisted analysis. Controlled mechanical stimulation (air jets, taps, pressure) was performed on the foot pads of all four limbs and on the hairy skin of the limbs and the body. 2. Long term recording of the spontaneous activity of 110 Purkyně cells revealed a simple spike activity of 85 imp./s ± 49 imp./s (mean ± S.D.) and 1.00 ± 0.78 climbing fiber responses per second. 3. Taps to foot pads and air jets to hairy skin revealed that most of the short latency responses via mossy fibers resulted from activation of the receptors of the ipsilateral forefoot. With the same stimuli climbing fiber discharges from the ipsilateral feet were more frequently evoked than from the contralateral feet. Both via mossy and climbing fibers the contralateral hindlimb gave the smallest contribution. 4. Simple spike responses were evoked more commonly by pad stimulation (tap stimuli) than by hair stimulation (air jets). For both types of stimuli excitatory responses were more frequent (3 ∶ 1) than inhibitory ones. Similarly, pad stimulation was more effective than hair stimulation in inducing climbing fiber responses. Ipsilateral stimuli were much more effective than contralateral ones in evoking both simple spike and climbing fiber responses. 5. Steady pressure stimuli modify the Purkyně cell discharges via mossy and climbing fiber pathways. Excitatory and inhibitory effects often of very long duration have been observed via both pathways. Again the ipsilateral forelimb was more effective than the other limbs. Mossy fiber responses were at least three times as common as climbing fiber responses and excitatory responses were more frequent than inhibitory ones. 6. There is no apparent relation between the spontaneous discharge rates of the Purkyně cells and the response magnitudes of the mossy fiber and climbing fiber induced excitatory and inhibitory changes in the impulse pattern of Purkyně cells during steady pressure stimuli.

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1432-1106

Mechanoreceptors ; Cutaneous Afferents ; Afterpotentials ; Primary Afferent Depolarization ; Spinal Cord

Springer Online Journal Archives 1860-2000

Medicine

Summary Mechanoreceptors of the hairy skin and the central pad of the cat's hind foot were activated using piezo-electric crystals as mechanical stimulators. Their afferent fibres were traced in the lumbar spinal cord by stimulating antidromically and by recording the collision of the antidromic and orthodromic action potentials. Low threshold mechanoreceptor units could be stimulated in isolation. It was possible, therefore, to follow the postspike excitability changes of their fibres in the spinal cord without interference from other spinal cord potentials. Primary afferent depolarization has been induced in cutaneous afferents by stimulating muscle and cutaneous nerves. It has been found that the a cutaneous fibres of mechanoreceptors were depolarized by volleys in a cutaneous fibres and to a lesser degree by volleys in Group I b, II and III muscle afferents but not by high threshold cutaneous afferents. The primary afferent depolarization of cutaneous fibres has been subjected to the action of an impulse propagating down that fibre to its central terminals. Excitability testing revealed that the amplitude and the time course of the primary afferent depolarization were only altered up to about 30 ms after the impulse indicating an active depolarization of the presynaptic terminals.

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1432-1106

Muscle group IV afferent units ; Muscle pain ; Chemo-nociceptors ; Mechanoreceptors ; Contraction-sensitive receptors

Springer Online Journal Archives 1860-2000

Medicine

Summary In an attempt to differentiate between nociceptive group IV muscle receptors and “ergoceptive” ones, the discharges of single group IV fibres from skeletal muscle in response to local pressure, sustained stretch, repetitive contraction and intra-arterial injections of bradykinin, 5-hydroxytryptamine (5-HT), potassium, phosphate, and lactate were studied in anaesthetized cats. Of the 75 fibres of the study, 5 units were activated by sustained stretch, the responses occurring with a delay. These stretch-sensitive units could not be activated by local pressure or muscular contraction. Thirteen group IV afferents raised their discharge frequency during repetitive contractions. Some of the units responded immediately with the onset of the contractions, whereas the others showed a pronounced delay. Forty-six units were tested with all or most of the above mechanical and chemical stimuli. In 32 afferents a response to at least one of the stimuli was present. Taking only these units into account, several groups of receptors could be distinguished by their different response combinations. One group was activated by pain-producing substances, but not by muscular activity and thus showed nociceptive properties. Another group showed a raised activity during muscular contractions but did not respond to the algesic agents bradykinin and 5-HT. Units belonging to this group might serve as “ergoceptors”. The borderline between the two groups was not sharp, a considerable number of group IV afferents was found which had both nociceptive and “ergoceptive” properties.

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1432-1106

Unanesthetized cat ; Cerebellum ; Purkyně cells ; Mossy fiber fields ; Climbing fiber fields ; Cutaneous mechanoreceptors

Springer Online Journal Archives 1860-2000

Medicine

Summary 1. In cats with local anaesthesia the cutaneous receptive fields of individual Purkyně cells of the vermis and pars intermedia of the anterior lobe were assessed by recording the simple spike discharges and climbing fiber responses following controlled mechanical stimulation of the foot pads of all four limbs (taps and pressure stimuli) and of the hairy skin (air jets) of the limbs and the body. 2. Exploring the receptive fields with taps and air jets revealed for the mossy fiber transmitted activity that in a population of 93 cells 37 had small receptive fields from the distal areas of one limb only; 28 had discontinuous receptive fields in two limbs and the others had their receptive fields on three or four limbs (multiple discontinuous fields) or over all or almost all of the body surface (widespread fields). 3. Testing with pressure stimuli to the toe pads inside and outside the receptive fields outlined with taps and air jets led to modifications of the simple spike discharges in 86 of 90 cells investigated in this way. Inclusion of these pressure fields increases the percentage of cells with discontinuous multiple mossy fiber transmitted receptive fields on three or four limbs to nearly 70% of our sample of Purkyně cells. 4. Approximately 50% of the cells with mossy fiber transmitted receptive fields also had climbing fiber transmitted fields. With the climbing fiber input the receptive fields were comparable with those for mossy fiber inputs when exploring with taps or air jets. Some additional climbing fiber transmitted cutaneous receptive fields were found with pressure stimuli. These pressure fields were usually restricted to one or two limbs. 5. These findings imply that the mossy fiber transmitted receptive fields of a given Purkyně cell usually extended over a wider area than the climbing fiber transmitted fields. As a rule the (small) climbing fiber fields were overlapped more or less completely by the (large) mossy fiber fields. 6. The receptive fields were either purely excitatory or partly excitatory and partly inhibitory. Pure inhibitory fields were rare. Within a mixed field no dominant pattern has been detected in regard to the arrangement of the excitatory and inhibitory areas. With the multiple fields from three or four limbs, receptive fields of complex composition seem to be the rule rather than the exception. It appears that in samples of cells like the present, each one has its own individuality in regard to shape and extent and in the intermingling of the excitatory and inhibitory field areas from mossy and climbing fiber inputs.

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1432-0568

Dura mater encephali ; Sensory receptors ; Nerve fibres ; Vascular bed ; Lymphatic vessel ; Nociception ; Headache

Springer Online Journal Archives 1860-2000

Medicine

Summary The dura mater encephali of the rat is richly supplied by myelinated (A-axons) and unmyelinated (C-axons) nerve fibres. For the supratentorial part the main nerve supply stems from all three branches of the trigeminal nerve. Finally, 250 myelinated and 800 unmyelinated nerve fibres innervate one side of the supratentorial part. The vascular bed of the dura mater exhibits long postcapillary venules up to 200 μm in length with segments of endothelial fenestration. Lymphatic vessels occur within the dura mater. They leave the cranial cavity through the openings of the cribriform plate, rostral to the bulla tympani together with the transverse sinus, and the middle meningeal artery. The perineural sheath builds up a tube-like net containing the A- and C-axons. It is spacious in the parietal dura mater and dense at the sagittal sinus along its extension from rostral to caudal and at the confluence of sinuses. Terminals of both the A- and C-axons are of the unencapsulated type. Unencapsulated Ruffini-like receptors stemming from A-axons are found in the dural connective tissue at sites where superficial cerebral veins enter the sagittal sinus and at the confluence of sinuses. The terminations of single A-axons together with C-fibre bundles mix up in their final course in one Schwann cell to build up multiaxonal units or terminations (up to 15 axonal profiles). A morphological differentiation is made due to the topography of these terminations; firstly, in different segments of the vascular bed: postcapillary venule, venule, the sinus wall, lymphatic vessel wall, and secondly, within the dura mater: inner periosteal layer, collagenous fibre bundles of the meningeal layer and at the mesothelial cell layer of the subdural space.

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1432-0568

Wallerian degeneration ; Muscle nerve ; Postganglionic nerve fiber ; Ramus communicans griseus ; Sympathectomy

Springer Online Journal Archives 1860-2000

Medicine

Summary In cats the time course of degeneration following lumbal sympathectomy was studied in the ramus communicans griseus (reg) and in the nerves to the triceps surae muscle using light and electron microscopic methods. The left lumbar sympathetic trunk including its rami communicantes was removed from L2 to S1 using a lateral approach. The animals were sacrificed between 2 and 48 days after the sympathectomy. Tissue samples were taken (a) one cm proximal to the entrance of the rcg into the spinal nerve, and (b) one cm proximal to the entrance of the nerve into the muscle belly. In the reg signs of degeneration can already be recognized in the myelinated as well as in the unmyelinated axons 48h after sympathectomy. The degenerative processes in the axons reach their peak activity at about 4 days p.o. They end a weck later. Signs of the reactions of the Schwann cells and of the endoneural cells can first be seen 2 days p.o. They are most pronounced around the 8th day p.o., and last at least up to the third week. Thereafter the cicatrization processes settled to a rather steady state (total observation period 7 weeks). In the muscle nerves the first signs of an axonal degeneration of the sympathetic fibers can be recognized 4 days after surgery. The signs of axonal degeneration are most striking about 8 days p.o. They have more or less disappeared another week later. The reactions of the Schwann cells also start on the fourth day but outlast the degenerative processes by some 8 days. Thus the degenerative and reactive processes in the reg precede those in the muscle nerves by 2 days early after surgery and by 6 days 3 weeks later. Seven weeks after surgery, fragments of folded basement lamella and Remak bundles with condensed cytoplasm and numerous flat processes are persisting signs of the degeneration. In addition to the differences in time course between the proximal and the distal site of observation, it was also noted that both the axonal degeneration and the reactions of the Schwann cells are more pronounced in the rcg than in the muscle nerve. For example there was abundant mitotic activity in the central endoneural and Schwann cells whereas we could not detect such activity in the periphery. It is concluded that the time course of degeneration and the intensity of the degenerative and reactive processes is, to a considerable extent, determined by the distance between the site of nerve section and the site from which the specimen is taken. Many of the conflicting data in the literature can be explained by this finding.

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1432-0568

Afferent nerve fiber ; Nociceptor ; Sensory terminal ; Tendon innervation ; Ultrastructure

Springer Online Journal Archives 1860-2000

Medicine

Summary In sympathectomized cats the innervation of the Achilles tendon by fine afferent nerve fibers was studied with semithin and ultrathin sections. Several different types of sensory endings of group III and group IV nerve fibers were identified. Of the five different types of endings in the group III range (T III endings), two are located within vessel walls. One of them ends in the circumference of the venous vessels (T III/VV). Its lanceolate terminals have characteristic receptor areas at their edges. The second type ends in the adventitia of lymphatic vessels (T III/LV). Its receptive areas are scattered along their terminal course. Two further group III endings ramify within the connective tissue compartments of the vessel-nerve-fascicles of the peritenonium externum and internum. One type is tightly surrounded by collagen fibrils (T III/PTic); the other terminates between the collagen fiber bundles (T III/PTgc). The latter arrangement recalls the ultrastructural relation between nerve terminals and collagen tissue in Golgi tendon organs. The fifth type innervates the endoneural connective tissue of small nerve fiber bundles (T III/EN). At least some of them come into close contact with bundles of collagen fibers which penetrate the perineural sheath to terminate within the endoneurium. The endings of group IV afferents (T IV endings) show a striking topographic relationship to the blood and lymphatic vessels of all connective tissue compartments of the Achilles tendon. They form penicillate endings which may contain granulated vesicles. In any event, they can easily be discriminated from the T III endings in the vessel walls. In close neighborhood to Remak bundles, a cell has been regularly found which fulfilled all ultrastructural criteria for mast cells. But this cell is not a mast cell proper because it is surrounded by a basal lamina (pseudo mast cell).

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1420-908X

Springer Online Journal Archives 1860-2000

Medicine

Abstract This study on the effects of capsaicin on primary afferents from normal knee joints of the cat was performed to further elucidate the mechanisms of articular pain evoked by an acute arthritis and by chemical irritants. It showed that close i.a. bolus injection of capsaicin (10−7–10−4 M) excites most fine articular afferents (conduction velocity ≤11.3 m/s) whereas fast units are not excited. Fine afferents with low to medium thresholds to knee joint movement are less readily excited by capsaicin than high threshold ones. The response to capsaicin is usually a rapid burst of impulses of a very short latency. This response pattern differs considerably from that seen after application of endogenous substances produced in inflammation. Thus capsaicin seems to differ in its mode of action from that of endogenous algesic substances.

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1420-908X

Springer Online Journal Archives 1860-2000

Medicine

Abstract Capsaicin applied to human skin provokes a response known as neurogenic inflammation. Neuropeptides (substance P, CGRP), released from afferent C-fiber terminals and histamine, secondarily released from mast cells, are supposed to participate in this reaction. We investigated the contribution of arachidonic acid and metabolic products to neurogenic inflammation, using a potent topically applied glucocorticoid and the corresponding vehicle. Arachidonic acid is liberated from membrane phospholipids by phospholipase A2, an enzyme that can be blocked by glucocorticoids. In 12 healthy volunteers, neurogenic inflammation was induced by capsaicin 1% on both upper forearms after 16 h of topical pretreatment with either prednicarbate or vehicle. Neurogenic inflammation was assessed by laser Doppler flowmetry and by planimetry of flare sizes. Prednicarbate significantly reduced the laser Doppler flow values inside the flare responses, as well as the flare sizes themselves. These results show that to some extent glucocorticoids reduce capsaicin-induced neurogenic inflammation.

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1420-908X

Springer Online Journal Archives 1860-2000

Medicine

Abstract Neurogenic inflammation is evoked by neuropeptides released from primary afferent terminals and, presumably, by other secondarily released inflammatory mediators. This study examines whether prostaglandins might participate in the development of neurogenic inflammation in humans and whether cyclooxygenase inhibitors have any anti-inflammatory effect on this type of inflammation. In healthy volunteers, neurogenic inflammation was elicited by epicutaneously applied capsaicin (1%), after systemic pretreatment with acetylsalicylic acid, or topically applied indomethacin compared to pretreatment with saline or vehicle, respectively. The extent of neurogenic inflammation was quantified by planimetry of visible flare size and recording the increase of superficial cutaneous blood flow (SCBF) with a laser Doppler flowmeter. Capsaicin-induced flare sizes and outside SCBF (both representing neurogenically evoked inflammation) were unaffected by acetylsalicylic acid or indomethacin. Only the capsaicin-induced increase of inside SCBF was attenuated by local pretreatment with indomethacin, reflecting the participation of prostaglandins in the inflammatory response of those areas which were in direct contact with capsaicin.

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1420-908X

Dipyrone ; Metamizol ; Spinal cord ; Afferent fibres ; Inflammatory pain

Springer Online Journal Archives 1860-2000

Medicine

Abstract Electrophysiological experiments in anesthetized cats and rats were performed in order to study the effects of dipyrone on single afferent fibers from the knee joint and on spinal cord neurons with knee joint input. The neurons were activated and/or rendered hyperexcitable by an acute inflammation in the knee joint. In the joint nerve in cats, intravenous dipyrone (25–100 mg/kg) reduced ongoing activity in 10/12 thinly myelinated afferents but only in 1/10 unmyelinated afferents; the responses to movements of the inflamed knee were reduced in 8/10 thinly myelinated but only in 3/10 unmyelinated units. The reduction of activity was significant 20–30 min after application and was maximal at 60–180 min. In the spinal cord of spinalized cats, intravenous dipyrone (25–100 mg/kg) reduced ongoing activity and/or responses to pressure onto the inflamed knee in 14/16 neurons and in non-spinalized rats similar effects were seen in 10/11 neurons. Effects on spinal cord neurons started 5–10 min after application and were maximal after 20–40 min. These data show pronounced suppression of inflammation-induced nociception by dipyrone and they suggest that the spinal cord is a major site of action of this compound.

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1420-908X

Springer Online Journal Archives 1860-2000

Medicine

Abstract The peripheral and central terminals of primary afferents of the cat's knee joint were studied with light- and electron microscopy (including HRP-transprot methods). The majority of these afferent fibres are unmyelinated or thinly myelinated. In the periphery, they terminate in non-corpuscular endings. A dense network of branching nerve fibres surround the blood vessels to terminate at the vessel walls or in the adjacent dense collagenous tissue. Besides the terminals the fibres show preterminal bulges which are assumed to represent additional transduction sites. This implies that the whole distal fibre portion has a receptive function. The spinal projection is located in lamina I and V–VII of the dorsal horn. This location parallels that of muscular and visceral fibres, pointing to the possibility of a common projection pattern for deep somatic afferent fibres in the spinal cord of the cat.

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1432-1106

Mechanoreceptors ; Pacinian corpuscles ; Cutaneous afferents ; Peripheral encoding ; Skin sensitivity

Springer Online Journal Archives 1860-2000

Medicine

Summary The properties of mechanosensitive units with large myelinated afferents were determined in the hairless skin of the central pad of the cat's hind foot, and the total afferent outflow from this region after short skin indentations and during constant force stimuli was measured in the plantar nerves. Basically three types of mechanosensitive units with afferent conduction velocities above 40 m/s were found: (a) receptors with the properties of Pacinian corpuscles (PC-receptors); (b) receptors which showed burst discharges for up to 500 ms after the onset of a constant force stimulus (RA-receptors); and (c) receptors which discharged throughout a constant force stimulus (SA-receptors). The afferent conduction velocities of these units were in the same range as those of receptors from the surrounding hairy skin. A considerable proportion of receptors from both skin areas had no collaterals in the dorsal columns. The afferent outflow after short skin indentations of up to 5 μ displacement consisted of impulses from PC-receptors only. Stimuli of 20 μ recruited between 50 and 100 afferent units of which less than 10% were other than PC-units. During constant force stimuli the afferent outflow came from SA-receptors only. Ten seconds after stimulus onset a 500 g stimulus evoked an afferent discharge of about 1000 imp/s and a 1000 g stimulus of about 1700 imp/s. At all times a power function of the form F=K · (S−S0)n related the afferent discharge F to the stimulus intensity S. The exponents were around n=0.5 and tended to increase in the course of the stimulus.

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1432-1106

[K+]0 Spinal cord ; Posterior articular nerve ; Knee joint ; Inflammation ; Pain ; Arthritis ; Nociception ; Cat

Springer Online Journal Archives 1860-2000

Medicine

Summary In 20 cats anaesthetized with alpha-chloralose and spinalized at the thoracolumbar junction we investigated the role of stimulation induced accumulation of extracellular potassium in the spinal cord in the processing of nociceptive discharges from the knee joint. For that we electrically stimulated the posterior articular nerve of the knee. We further performed innocuous and noxious stimulation of the knee and of other parts of the leg and studied the effect of an acute inflammation of the knee on [K+]0 in the spinal cord. Innocuous stimulation of the skin (brushing or touching) and innocuous movements in the knee joint all induced rises in [K+]0 which were maximal at recording depths of 1500 to 2200 μm below the surface of the cord dorsum. Peak increases were 0.4 mM for touching the leg and 1.7 mM during rhythmic flexion/ extension of the knee joint. Noxious stimulation of the skin, the paw, the tendon and noxious movements of the knee joint also produced rises in [K+]0, which were somewhat larger for the individual types of stimuli than those produced by innocuous intensities. Electrical stimulation of the posterior articular nerve induced rises in [K+]0 by up to 0.6 mM. Stimulus intensities sufficient to activate unmyelinated group IV fibers were only slightly effective in raising [K+]0 above the levels reached during stimulation of myelinated group II and III fibers. During development of an acute inflammation of the knee joint (induced by kaolin and carrageenan), increases in [K+]0 and associated field potentials became larger by about 25%. We assume that this reflects an increase in neuronal responses. In conclusion, changes in [K+]0 in the spinal cord are some-what larger during noxious stimulation than during innocuous stimulation. The absolute level reached depended more on the site and type of stimulation than on the actual stimulus intensity itself. Hence a critical role of spinal K+ accumulation for nociception is unlikely.

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1432-1106

Pain ; Inflammation ; Descending inhibition ; Nociception ; Spinal cord ; Cat

Springer Online Journal Archives 1860-2000

Medicine

Summary In ten cats, single unit electrical activity was recorded in the lumbosacral spinal cord from neurones driven by stimulation of afferent fibres from the ipsilateral knee joint. Tonic descending inhibition (TDI) on the responses of these cells was measured as increases in resting and evoked activity of the neurones following reversible spinalization of the animals with a cold block at upper lumbar level. Acute inflammation of the knee joint was induced in five of the cats by the injection of kaolin and carrageenan into the joint. TDI was observed in 25 of 33 neurones recorded in normal animals (76%) and in 36 of 40 (90%) neurones recorded in animals with acute knee joint inflammation. In both kinds of preparation TDI was more pronounced in neurones recorded in the deep dorsal horn and in the ventral horn than in those recorded in the superficial dorsal horn. There was a tendency in the whole sample for TDI to be greater in neurones with input from inflamed knees. We conclude that the spinal processing of afferent information from joints is under tonic descending influences and that the amount of TDI can be altered during acute arthritis.

Electronic Resource

1432-1106

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1432-1106

Cutaneous afferents ; Primary afferent depolarization ; Presynaptic inhibition ; Surround inhibition ; Spinal cord

Springer Online Journal Archives 1860-2000

Medicine

Summary In five types of mechanoreceptor afferents of the cat's hind foot, the primary afferent depolarization (PAD) induced by mechanical skin stimulation was measured by testing the excitability of their terminations in the dorsal horn. Two types of skin stimuli were used to set up activity in distinct populations of rapidly and slowly adapting mechanoreceptors respectively. The experiments revealed that two systems exist to generate PAD in cutaneous afferents, both being of negative feedback character. One system is activated by impulses from rapidly adapting low threshold receptors and preferentially depolarizes the terminals of such afferents, and correspondingly, the other system is activated by and operates on the slowly adapting units. In both PAD systems the size of the depolarization is graded depending on the stimulus strength. Further, the “tonic” system displays a “surround” pattern of organization similar to that of the “phasic” system which has already been described (Schmidt et al. 1967b). In the discussion the operational relationships of both systems and their functional implications are outlined.

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