Stimulation Of Deep Tissues Research Articles

Long-term changes in discharge behaviour of cat dorsal horn neurones following noxious stimulation of deep tissues

Certain pathological types of afferent input are supposed to lead to long-term changes in the responsiveness of dorsal horn neurones. This mechanism might be of importance for the development of neurological disturbances such as chronic pain. The present study was undertaken in order to find out whether dorsal horn neurones— particularly those processing input from deep tissues— exhibit long-lasting changes in response behaviour after a short-lasting noxious stimulation of deep tissue. In anaesthetized cats, the impulse activity of single dorsal horn cells was recorded extracellularly with glass microelectrodes. In a small number of cells that had multiple receptive fields (RFs), the algesic agent bradykinin was injected into a muscle RF and the properties of all RFs retested at regular time intervals. Following noxious chemical stimulation of one RF, the injected and the other RFs of the same neurone often showed changes which consisted of an increase in size, a lowering of mechanical threshold and appearance of new RFs. In an attempt to assess the influence of a single noxious stimulus on the entire population of dorsal horn cells, the properties of a greater sample of neurones were compared before and after injection of bradykinin into the deep tissues of the hind limb. Every cell encountered was classified as being driven by (1) cutaneous receptors only, (2) deep receptors only, (3) both input sources, or (4) electrical stimulation only (cell without receptive field). Following injection of bradykinin, the proportion of cells with both deep and cutaneous input and of those having background activity rose, and the percentage of cells without a receptive field decreased. The data indicate that any noxious manipulation of the hind limb may elicit long-lasting changes in the response behaviour of dorsal horn neurones. This assumption was supported by the finding that in animals in which the hind limb had been operated on, the proportion of cells with deep and cutaneous input was significantly higher and that of cells with exclusively deep input lower than in animals with an intact hind limb. Transferring these findings to the clinical situation, the data suggest that the increase in size of the RFs and the appearance of new RFs after a noxious stimulus might reflect the spread or irradiation of deep pain. Likewise, the increase in convergence of deep and cutaneous afferents might be of relevance for the referral of deep pain to the skin, while the decrease in mechanical threshold of deep RFs remote to the location of the noxious stimulus might be the neurophysiological basis of referred tenderness.

Activation of dorsal horn cells by ventral root stimulation in the cat.

Responses of dorsal horn cells to ventral root stimulation were determined for the L7 and S1 levels of the spinal cord of 14 anesthetized cats. Forty-six dorsal horn cells were found that were excited by stimulation of the distal stump of the cut ventral root. For maximum excitation it was necessary to use a train of stimuli. For the 34 dorsal horn cells whose peripheral receptive-field properties could be characterized, 14 were wide dynamic range cells and 19 were high-threshold cells. The other cell responded exclusively to stimulation of deep tissue. None of the cells responded exclusively to innocuous stimuli, and all responded more vigorously to noxious than to innocuous stimuli. Some cells also responded to noxious heat applied to the skin of the receptive field. Locations of 10 of the activated dorsal horn cells were identified. They were distributed throughout the dorsal horn, but most were found in laminae V and VI. In four animals, both the proximal and distal stumps of the cut S1 ventral root were stimulated while searching for dorsal horn cells. Ten dorsal horn cells were found that were excited by stimulation of the distal stump of the ventral root. No cells were found that responded to proximal stump stimulation. To prevent current spread by stimulation of the ventral root, an extra ground electrode was placed distal to the stimulating electrodes. When the ground electrode was removed, distinctive signs of current spread appeared in that a cord dorsum potential could be recorded and the dorsal horn neuronal responses changed. Dorsal horn neurons could also be excited by nonelectrical stimuli such as crushing the ventral root. If the ventral root was crushed distal to the stimulating electrodes, however, the initially excited cell could no longer be activated by ventral root stimulation. Activation of dorsal horn cells by stimulation of the distal stump of a cut ventral root was abolished when the dorsal root of the same segment was sectioned. Conduction velocities of the fibers in the ventral root that excited dorsal horn cells ranged between 0.25 and 1.78 m/s with a mean of 0.91 +/- 0.47 (SD) m/s. These results show that there are unmyelinated afferent fibers in the ventral root that enter the spinal cord through the dorsal root and excite dorsal horn cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution patterns of individual medial lemniscal axons in the ventrobasal complex of the monkey thalamus.

Twenty-seven medial lemniscal axons were traced to their terminations in the thalamic ventrobasal complex of monkeys, following injection of horseradish peroxidase into the lemniscus at midbrain levels. Most axons had terminal ramifications at one horizontal level in the ventrobasal complex. All terminations were focal, many were anteroposteriorly elongated, though none were sufficiently long to occupy more than one-third to one-half of the anteroposterior extent of the VPLc nucleus. All terminal ramifications were compressed sagittally into a slab 200-300 micrometers wide. There was modest overlap in the terminal territories of adjacent labelled axons and, as judged light microscopically, only a small amount of convergence onto the vicinities of single cells. Axons terminating selectively in the anterodorsal shell or central core of VPLc could be identified. In the anterodorsal shell (of neurons responding to stimulation of deep tissues) axons tended to terminate either in the part projecting to area 3a or in that projecting to areas 3a and 2 of the cortex. In the central core (of neurons responding to cutaneous stimulation and projecting to areas 3b and 1) larger ramifications were present in its center and smaller ramifications in its ventral part. A few axons had terminal ramifications at two dorsoventral levels in the cutaneous core; others had terminations in both the dorsal deep shell and the cutaneous core. In both cases, one ramification was always smaller than the other. The termination of lemniscal axons at defined foci instead of along the dorsoventral extent of the representational lamellae of the ventrobasal complex has implications for the nature of the body representation in the nuclei. Their tendency to be focal implies that not all members of an anteroposteriorly elongated rod of place-and-modality-specific ventrobasal cells that project their axon to a single column in the somatic sensory cortex receive afferent inputs from the same lemniscal fibers.

Patterns of responses of neurons in cuneate nucleus to controlled mechanical stimulation of cutaneous velocity receptors in the cat.

1. The responses of single cuneate neurons to controled mechanical stimulation of skin were recorded in cats lightly anesthetized with a nitrous oxide-halothane mixture. The discharge patterns and peripheral receptive-field characteristics were studied in neurons driven by sensitive cutaneous mechanoreceptors, including slowly adapting skin mechanoreceptors. Virtually all cuneate neurons display maximum discharge during the velocity component of displacement. 2. Among cuneate neurons encountered in this study, approximately 46% were driven by guard hair mechanoreceptors, 15% were driven by field receptors, and 13% were driven by slowly adapting skin receptors. Neurons responding to stimulation of deep tissues (including claws) were not studied with controlled mechanical stimulation and accounted for 19%. The rest of the neurons were driven by Pacinian corpuscles, received afferent inputs from several different first-order afferents, or were not definitely identified. There was no clear evidence of down hair or high-threshold mechanoreceptor representation. 3. The discharge pattern in response to a constant-velocity stimulus proved most valuable in describing submodality classes of neurons driven by hair and field receptors since sensitivity of these neurons to dynamic and to static phases of stimulation constitute respective continua and, thus, preclude sharp separation into distinct groups. 4. The majority of neurons displayed response properties and receptive fields similar to those of first-order afferents. A minority of cells had receptive fields that were larger than those of primary afferents, with nearly identical modality and velocity characteristics throughout the receptive field. 5. Approximately 2% of recorded neurons displayed convergent properties not encountered in first-order afferents, including neurons driven from receptors of different modalities or from discontinuous receptive fields. 6. Inhibition of neuronal firing generated from outside the receptive field was rarely seen, possibly due to anesthetic conditions. In a small number of neurons, irregularities in the discharge were observed that might indicate inhibitory influences originating from within the receptive field.

Relationship between afferent input and motor output in sensorimotor cortex of the monkey

Single-cell recording and intracortical stimulation were used to study input-output relations in the sensorimotor cortex of rhesus and Java monkeys anesthetized with sodium pentobarbital. The receptive fields of individual cortical cells were compared with the loci of movements or muscle contractions evoked by electrical stimulation near these cells. Data were obtained from 101 single neurons in the rhesus monkey and 36 neurons in the Java monkey. Two-thirds of the cells in postcentral gyrus responded to cutaneous stimulation and one-third to stimulation of deep tissues (passive joint movement, deep pressure). Only 19 cells were recorded in precentral gyrus that could be driven by somatosensory input. Electrical stimulation within both cortical regions typically evoked discrete contralateral movements or muscle contractions. Stimulus thresholds were almost two times higher in postcentral gyrus than in precentral gyrus. The somatic origin of sensory input to a given cortical site was correlated in a general way with the somatic target of motor output from that cortical site. However, input-output coupling was relatively loose, since the receptive fields of cortical neurons often did not overlap with the peripheral locus of minimal cortically evoked movements.

Somatic and visceral receptive field properties of fibers in ventral quadrant white matter of the cat spinal cord.

Somatic and visceral receptive field properties of fibers in ventral quadrant white matter of the cat spinal cord.H L Fields, L D Partridge Jr, and D L WinterH L Fields, L D Partridge Jr, and D L WinterPublished Online:01 Nov 1970https://doi.org/10.1152/jn.1970.33.6.827MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySympathetic activation of cat spinal neurons responsive to noxious stimulation of deep tissues in the low backPain, Vol. 56, No. 1Analgesia produced by intrathecal administration of the k opioid agonist, U-50,488H, on formalin-evoked cutaneous pain in the ratEuropean Journal of Pharmacology, Vol. 190, No. 3Visceral pain: a review of experimental studiesPain, Vol. 41, No. 2The response of neurons of the medial pontomedullary reticular formation of rats to peripheral thermal stimuliBrain Research, Vol. 336, No. 1Cardiovascular and T2–T4 dorsal horn cell responses to gallbladder distention in the catBrain Research, Vol. 321, No. 2The spinomesencephalic tract in the cat: Its cells of origin and termination pattern as demonstrated by the intraaxonal transport methodBrain Research, Vol. 291, No. 1Noxious intensities of visceral stimulation are required to activate viscerosomatic multireceptive neurons in the thoracic spinal cord of the catBrain Research, Vol. 240, No. 2Peripheral and central substrates involved in the Rostrad transmission of nociceptive informationPain, Vol. 13, No. 1Somatic responses of ventrobasal thalamic neurones in polyarthritic ratsBrain Research, Vol. 237, No. 2Responses of spinothalamic tract cells in the thoracic spinal cord of the monkey to cutaneous and visceral inputsPain, Vol. 11, No. 2Convergence of cutaneous and pelvic visceral nociceptive inputs onto primate spinothalamic neuronsPain, Vol. 11, No. 2Organization of the sacral parasympathetic reflex pathways to the urinary bladder and large intestineJournal of the Autonomic Nervous System, Vol. 3, No. 2-4Viscerosomatic convergence and responses to intestinal distension of neurons at the junction of midbrain and posterior thalamus in the catExperimental Neurology, Vol. 70, No. 2Neurones responding to noxious stimulation in VB complex and caudal adjacent regions in the thalamus of the ratPain, Vol. 8, No. 3Natural stimulation of urinary bladder afferents does not affect transmission through lumbosacral spinocervical tract neurones in the catBrain Research, Vol. 156, No. 2Antinociceptive effects of vaginal stimulation in rats: Neurophysiological and behavioral studiesBrain Research, Vol. 137, No. 1Responses of thoracic dorsal horn interneurons to cutaneous stimulation and to the administration of algogenic substances into the mesenteric artery in the spinal catBrain Research, Vol. 124, No. 3Somatosensory properties of spinoreticular neurons in the catBrain Research, Vol. 120, No. 1Role of the reticular formation in responses to noxious stimulationPain, Vol. 2, No. 4Responses of sympathetic postganglionic neurons to peripheral nerve stimulation in the pigeon (Columba livia)Experimental Neurology, Vol. 49, No. 2Response properties and anatomical organization of pontine and medullary units responsive to vaginal stimulation in the catBrain Research, Vol. 97, No. 1Convergence of visceral and cutaneous input onto spinothalamic tract cells in the thoracic spinal cord of the catExperimental Neurology, Vol. 47, No. 2Some properties of spinal neurons projecting to the medial brain-stem reticular formationExperimental Neurology, Vol. 47, No. 1Convergence in the lumbar spinal cord of pathways activated by splanchnic nerve and hind limb cutaneous nerve stimulationExperimental Neurology, Vol. 38, No. 2 More from this issue > Volume 33Issue 6November 1970Pages 827-37 https://doi.org/10.1152/jn.1970.33.6.827PubMed5485405History Published online 1 November 1970 Published in print 1 November 1970 Metrics

Unit discharges recorded from dorsal portion of medulla responding to adequate exteroceptive and proprioceptive stimulation in cats.

1. In a series of intercollicular decerebrated and decerebellated cats, the dorsal part of the lower medulla was explored in search for the modality and topographical arrangement of the spinal afferents, employing microelectrodes inserted freehand. All the responses were produced by mechanical deformation of peripheral tissues and were obtained ipsilaterally.2. The responses observed were classified into three groups:(a) unit discharges responding to stimulation of deep tissues, showing slow adaptation (proprioceptive afferent)(b) unit discharges to movement of hairs or light touch on the skin, showing quick adaptation (tactile afferents) and (c) unit discharges driven by pressure upon the skin, showing slow adaptation (pressure afferents).3. The tactile afferents were most frequently encountered in the gracile nucleus, while the proprioceptive afferents from deep structures were the commonest pattern in the cuneate nucleus. In the restiform body, the responses to hind limb stimulation were the commonest patter. n For any part of the body, the proprioceptive, pressure and tactile afferents were found in the decreasing order of occurrence. The paraalar area resembled the rstiform body in the modalities of the afferents projecting thereto. The major component of the fibers terminating in the paraalar area were from the hind limb via the dorsolateral funiculus. The proprioceptive afferents were the commonest pattern, but occurrence of the pressure afferents was relatively high.