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The Journal of Physiology Jul 19771. The responses of identified cells in the cat Clarke's column and dorsal horn to micro-electrophoretically applied cholinomimetics and anti-cholinergic substances have...
1. The responses of identified cells in the cat Clarke's column and dorsal horn to micro-electrophoretically applied cholinomimetics and anti-cholinergic substances have been investigated. 2. Both antidromically identified (DSCT neurones) and synaptically activated neurones from the region of the Clarke's column of the spinal cord were excited by ACh. However, the proportion of ACh excited cells was greater in units synaptically activated by ipsilateral dorsolateral funiculus stimulation (78%) than in DSCT neurones (50%). In addition, about 55% of neurones activated either antidromically or synaptically by ipsilateral dorsal column stimulation were excited by ACh. 3. In contrast to a relatively weak excitatory potency on the DSCT neurones (maximum firing frequency did not exceed 130% of the control activated by ipsilateral dorsolateral funiculus stimulation (maximum firing frequency reached 430% of the control level). 4. ACh has a relatively quick and rapidly reversible excitatory effect on Clarke's column neurones and some types of dorsal horn interneurones, which can be obtained also with nicotine. However, the action of nicotine is frequently delayed in onset and recovery. This excitatory action of ACh can be blocked or markedly depressed by dihydro-beta-erythroidine. These results and those obtained with acetyl-beta-methylcholine and atropine seem to suggest that the receptors mediating excitation of the cholinoceptive spinal cells activated either antidromically or synaptically by ipsilateral dorsolateral funiculus stimulation besides predominantly nicotinic have also weak muscarinic properties. 5. Desensitization with repeated applications of ACh and nicotine has been observed in both DSCT neurones and units antidromically activated by ipsilateral dorsal column stimulation. 6. About 11% of units antidromically activated by ipsilateral dorsolateral funiculus stimulation were depressed by ACh. In addition, the depressant effect of ACh was more frequently encountered in the cells unresponsive either to the dorsolateral funiculus or dorsal column stimulation. ACh depression was also seen in units activated either antidromically or synaptically by ipsilateral dorsal column stimulation. In contrast, none of the units synaptically activated by the ipsilateral dorsolateral funiculus stimulation were depressed by ACh. The same was true for spinal neurones receiving convergent peripheral inputs activated either antidromically or synaptically by ipsilateral dorsolateral or dorsal column stimulation. 7. The findings that ACh depression of all tested DSCT neurones is blocked by atropine and readily evoked by acetyl-beta-methylcholine indicates that receptors mediating the effect are of muscarinic type.
Topics: Acetylcholine; Animals; Atropine; Cats; Choline; Dihydro-beta-Erythroidine; Electrophoresis; Evoked Potentials; Female; Interneurons; Male; Methacholine Compounds; Neurons; Nicotine; Spinal Cord
PubMed: 894542
DOI: 10.1113/jphysiol.1977.sp011899 -
The Journal of Comparative Neurology Dec 2022Our knowledge about the detailed wiring of neuronal circuits in the spinal dorsal horn (DH), where initial sensory processing takes place, is still very sparse. While a...
Quantitative spatial analysis reveals that the local axons of lamina I projection neurons and interneurons exhibit distributions that predict distinct roles in spinal sensory processing.
Our knowledge about the detailed wiring of neuronal circuits in the spinal dorsal horn (DH), where initial sensory processing takes place, is still very sparse. While a substantial amount of data is available on the somatodendritic morphology of DH neurons, the laminar and segmental distribution patterns and consequential function of individual axons are much less characterized. In the present study, we fully reconstructed the axonal and dendritic processes of 10 projection neurons (PNs) and 15 interneurons (INs) in lamina I of the rat, to reveal quantitative differences in their distribution. We also performed whole-cell patch-clamp recordings to test the predicted function of certain axon collaterals. In line with our earlier qualitative description, we found that lamina I INs in the lateral aspect of the superficial DH send axon collaterals toward the medial part and occupy mostly laminae I-III, providing anatomical basis for a lateromedial flow of information within the DH. Local axon collaterals of PNs were more extensively distributed including dorsal commissural axon collaterals that might refer to those reported earlier linking the lateral aspect of the left and right DHs. PN collaterals dominated the dorsolateral funiculus and laminae IV-VI, suggesting propriospinal and ventral connections. Indeed, patch-clamp recordings confirmed the existence of a dorsoventral excitatory drive upon activation of neurokinin-1 receptors that, although being expressed in various lamina I neurons, are specifically enriched in PNs. In summary, lamina I PNs and INs have almost identical dendritic input fields, while their segmental axon collateral distribution patterns are distinct. INs, whose somata reside in lamina I, establish local connections, may show asymmetry, and contribute to bridging the medial and lateral halves of the DH. PNs, on the other hand, preferably relay their integrated dendritic input to deeper laminae of the spinal gray matter where it might be linked to other ascending pathways or the premotor network, resulting in a putative direct contribution to the nociceptive withdrawal reflex.
Topics: Rats; Animals; Receptors, Neurokinin-1; Spinal Cord; Axons; Interneurons; Posterior Horn Cells; Neurons; Spatial Analysis; Perception
PubMed: 36094014
DOI: 10.1002/cne.25413 -
The Journal of Physiology Apr 2010The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated...
The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated the loss of low but not high threshold penile inputs to medullary reticular formation (MRF) neurons after acute and chronic dorsal column (DC) lesions of the T8 spinal cord and loss of all penile inputs after lesioning the dorsal three-fifths of the cord. In the present study, select T8 lesions were made and terminal electrophysiological recordings were performed 45-60 days later in a limited portion of the nucleus reticularis gigantocellularis (Gi) and Gi pars alpha. Lesions included subtotal dorsal hemisections that spared only the lateral half of the dorsal portion of the lateral funiculus on one side, dorsal and over-dorsal hemisections, and subtotal transections that spared predominantly just the ventromedial white matter. Electrophysiological data for 448 single unit recordings obtained from 32 urethane-anaesthetized rats, when analysed in groups based upon histological lesion reconstructions, revealed (1) ascending bilateral projections in the dorsal, dorsolateral and ventrolateral white matter of the spinal cord conveying information from the male external genitalia to MRF, and (2) ascending bilateral projections in the ventrolateral white matter conveying information from the pelvic visceral organs (bladder, descending colon, urethra) to MRF. Multiple spinal pathways from the penis to the MRF may correspond to different functions, including those processing affective/pleasure/motivational, nociception, and mating-specific (such as for erection and ejaculation) inputs.
Topics: Afferent Pathways; Animals; Electrophysiological Phenomena; Male; Medulla Oblongata; Penis; Pleasure; Rats; Rats, Wistar; Reticular Formation; Spinal Cord; Spinal Cord Injuries; Urinary Bladder
PubMed: 20142271
DOI: 10.1113/jphysiol.2009.186544 -
Innovative Surgical Sciences Mar 2017Axon visualization techniques are important in assessing the efficacy of interventional approaches to stimulate neural regeneration. Whereas the labeling of descending...
Axon visualization techniques are important in assessing the efficacy of interventional approaches to stimulate neural regeneration. Whereas the labeling of descending tracts in the spinal cord has been well established using the intracortical injection of biotin dextran amine (BDA), the labeling of ascending sensory fibers of the dorsal funiculus is more problematic. Fluoro-Ruby (FR; dextran tetramethylrhodamine; MW 10,000) is a bidirectional permanent tracer, but the retrograde tracing of fibers is particularly prominent, and FR is a highly sensitive tracer that can be applied in discrete injection sites. In the present report, we used FR to efficiently label ascending fibers in the dorsal columns of the rat spinal cord. After transplantation of olfactory ensheathing cells into the transected dorsal funiculus, the application of FR was able to detect regenerating ascending fibers in the spinal cord. Regenerated fibers crossing the injury site were labeled and easily identified. It is likely that the tracer was taken up by damaged fibers. As additional advantages, the labeling is resistant to photobleaching and no additional tissue processing is necessary for visualization. It can be used for as well as injections. The findings indicate that FR can be used as a reliable fluorescent marker to study ascending regenerated fibers in the spinal cord axonal regeneration.
PubMed: 31579728
DOI: 10.1515/iss-2016-0019 -
Experimental Neurology May 2017Enabling motor control by epidural electrical stimulation of the spinal cord is a promising therapeutic technique for the recovery of motor function after a spinal cord...
Enabling motor control by epidural electrical stimulation of the spinal cord is a promising therapeutic technique for the recovery of motor function after a spinal cord injury (SCI). Although epidural electrical stimulation has resulted in improvement in hindlimb motor function, it is unknown whether it has any therapeutic benefit for improving forelimb fine motor function after a cervical SCI. We tested whether trains of pulses delivered at spinal cord segments C6 and C8 would facilitate the recovery of forelimb fine motor control after a cervical SCI in rats. Rats were trained to reach and grasp sugar pellets. Immediately after a dorsal funiculus crush at C4, the rats showed significant deficits in forelimb fine motor control. The rats were tested to reach and grasp with and without cervical epidural stimulation for 10weeks post-injury. To determine the best stimulation parameters to activate the cervical spinal networks involved in forelimb motor function, monopolar and bipolar currents were delivered at varying frequencies (20, 40, and 60Hz) concomitant with the reaching and grasping task. We found that cervical epidural stimulation increased reaching and grasping success rates compared to the no stimulation condition. Bipolar stimulation (C6- C8+ and C6+ C8-) produced the largest spinal motor-evoked potentials (sMEPs) and resulted in higher reaching and grasping success rates compared with monopolar stimulation (C6- Ref+ and C8- Ref+). Forelimb performance was similar when tested at stimulation frequencies of 20, 40, and 60Hz. We also found that the EMG activity in most forelimb muscles as well as the co-activation between flexor and extensor muscles increased post-injury. With epidural stimulation, however, this trend was reversed indicating that cervical epidural spinal cord stimulation has therapeutic potential for rehabilitation after a cervical SCI.
Topics: Analysis of Variance; Animals; Biophysics; Cervical Vertebrae; Disease Models, Animal; Electromyography; Evoked Potentials, Motor; Female; Forelimb; Hand Strength; Range of Motion, Articular; Rats; Rats, Long-Evans; Recovery of Function; Spinal Cord Injuries; Spinal Cord Stimulation
PubMed: 28192079
DOI: 10.1016/j.expneurol.2017.02.006 -
Clinical & Developmental Immunology 2013The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following...
The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following central nervous system (CNS) injury. Our laboratory has previously demonstrated that immunological demyelination of the CNS facilitates regeneration of severed axons following spinal cord injury. In the present study, we evaluate whether immunological demyelination is accompanied with astrogliosis. We compared the astrogliosis and macrophage/microglial cell responses 7 days after either immunological demyelination or a stab injury to the dorsal funiculus. Both lesions induced a strong activated macrophage/microglial cells response which was significantly higher within regions of immunological demyelination. However, immunological demyelination regions were not accompanied by astrogliosis compared to stab injury that induced astrogliosis which extended several millimeters above and below the lesions, evidenced by astroglial hypertrophy, formation of a glial scar, and upregulation of intermediate filaments glial fibrillary acidic protein (GFAP). Moreover, a stab or a hemisection lesion directly within immunological demyelination regions did not induced astrogliosis within the immunological demyelination region. These results suggest that immunological demyelination creates a unique environment in which astrocytes do not form a glial scar and provides a unique model to understand the putative interaction between astrocytes and activated macrophage/microglial cells.
Topics: Animals; Astrocytes; Cell Survival; Demyelinating Diseases; Female; Gliosis; Macrophage Activation; Macrophages; Microglia; Nerve Tissue Proteins; Rats; Spinal Cord Injuries
PubMed: 24319469
DOI: 10.1155/2013/812456 -
The Journal of Physiology Sep 19671. The topographic organization of first order afferent fibres in the lumbar, sacral and coccygeal dorsal roots, and in the fasciculus gracilis was studied in squirrel...
1. The topographic organization of first order afferent fibres in the lumbar, sacral and coccygeal dorsal roots, and in the fasciculus gracilis was studied in squirrel monkeys.2. At the entry zone, progressing from caudal to rostral, dorsal root filaments receive fibres from tail and hind-limb receptive fields which serially overlap and describe a spiral-shaped trajectory. The latter starts with tail, progresses post-axially towards the foot, crosses the foot from lateral to medial, and ascends the preaxial leg.3. In the fasciculus gracilis, this arrangement of fibres at the dorsal root entry zone is preserved in its entirety. It assumes the form of a fibre lamination, with the most caudal dorsal root fibres occupying a dorso-medial location; further rostral dorsal root fibres come to lie more ventrolaterally.4. Dorsum and sole of foot project in an overlapping and interdigitating manner to the fibre lamina of the 7th lumber dermatome in the fasciculus gracilis. Thereby, dorsum and sole of foot behave in the projection as if they were one and the same surface.5. The argument is presented that the foot and its projection on to the cross-sectional plane of the dorsal funiculus are topologically equivalent and that the hind-limb as a whole and its projection are not. On the other hand, homotopic mapping of the foot together with the sequential fibre organization in the dorsal funiculus enable many more types of closed curves on the body surface to remain arc-wise connected in the projection than would otherwise be possible.
Topics: Animals; Electrophysiology; Haplorhini; Hindlimb; Neurons; Peripheral Nerves; Skin; Spinal Nerves; Tail
PubMed: 4963874
DOI: 10.1113/jphysiol.1967.sp008292 -
American Journal of Physiology.... Mar 2008Neurons in the medullary reticular formation (MRF) of the rat receive a vast array of urogenital inputs. Using select acute and chronic spinal cord lesions to identify...
Neurons in the medullary reticular formation (MRF) of the rat receive a vast array of urogenital inputs. Using select acute and chronic spinal cord lesions to identify the location of the ascending neural circuitries providing either direct or indirect inputs to MRF from the penis, our previous studies demonstrated that the dorsal columns and dorsal half of the lateral funiculus convey low- and high-threshold inputs, respectively. In the present study, the gracile nucleus was targeted as one of the likely sources of low-threshold information from the penis to MRF. Both electrophysiological recordings and neuroanatomical tracing [injection of cholera toxin B subunit (CTB) into a dorsal nerve of the penis] were used. After discrimination of a single neuron responding to penile stimulation, testing for somatovisceral convergence was done (mechanical stimulation of the distal colon and the skin over the entire hindquarters). In 12 rats, a limited number of neurons (43 in total) responded to penile stimulation. Many of these neurons also responded to scrotal stimulation (53.5%, dorsal and/or ventral scrotum) and/or prepuce stimulation (46.5%). Histological reconstruction of the electrode tracks showed that the majority of neurons responding to penile stimulation were located ventrally within the medial one-third of the gracile nucleus surrounding obex. This location corresponded to sparse innervation by CTB-immunoreactive primary afferent terminals. These results indicate that neurons in the gracile nucleus are likely part of the pathway that provides low-threshold penile inputs to MRF, a region known to play an important role in mating processes.
Topics: Animals; Cholera Toxin; Electrophysiology; Immunohistochemistry; Male; Medulla Oblongata; Microelectrodes; Microscopy, Confocal; Neural Pathways; Neurons, Afferent; Penis; Physical Stimulation; Presynaptic Terminals; Rats; Rats, Wistar
PubMed: 18171689
DOI: 10.1152/ajpregu.00656.2007 -
The Journal of Neuroscience : the... Jun 1981Leu-enkephalin is an opioid peptide that has been found to modulate nociception in the spinal cord. Both pre- and postsynaptic interactions by enkephalins have been...
Leu-enkephalin is an opioid peptide that has been found to modulate nociception in the spinal cord. Both pre- and postsynaptic interactions by enkephalins have been proposed. By the peroxidase . anti-peroxidase immunocytochemical method, we studied the distribution and ultrastructure of neuronal elements in the monkey dorsal horn to elucidate possible morphological substrates for postulated opioid actions. Biochemical analysis of immunoreactive Leu-enkephalin-like peptides in the cord was performed to characterize the forms present in labeled neurons and terminals. At the light microscopic level, fiber immunostaining was found in most areas of gray matter, especially in laminae I to V, and in the dorsolateral funiculus. Cell bodies were located in laminae I, II, III, and V. At the ultrastructural level, in the superficial dorsal horn, we found that neurons with Leu-enkephalin receive numerous types of axon inputs, some of which have been identified previously as originating from the dorsal root. Leu-enkephalin terminals formed primarily axosomatic and axodendritic synapses and less frequently synapsed with other axons. With the same Leu-enkephalin antiserum as used in the immunocytochemistry, a peptide physicochemically similar to intact Leu-enkephalin and two larger Leu-enkephalin-like peptides were identified in monkey spinal cord extracts. It is likely that a family of Leu-enkephalin-like peptides is present in monkey spinal cord and that the labeled elements may contain any or all of these substances. It is concluded that both pre- and postsynaptic physiologic effects of Leu-enkephalin are possible, although the preponderance of axodendritic synapses favors a principal postsynaptic site of action. The anatomical results suggest that neurons containing immunoreactive Leu-enkephalin in the dorsal horn, some of which may receive input from primary afferents, modulate nociception by directly synapsing with cells of origin of the spinothalamic tract and also by interacting with primary afferent terminals.
Topics: Animals; Axons; Chromatography, High Pressure Liquid; Endorphins; Enkephalin, Leucine; Enkephalins; Macaca fascicularis; Microscopy, Electron; Neurons; Spinal Cord; Synapses; Synaptic Transmission; Tissue Extracts
PubMed: 6286896
DOI: 10.1523/JNEUROSCI.01-06-00561.1981 -
Brain, Behavior, and Immunity Jul 2020The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central...
The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central inflammation, which alters central respiratory control and viscerosensory transmission in the nucleus tractus solitarii (nTS). These functional changes coincide with increased interleukin-1 beta (IL-1β) in the area postrema, a sensory circumventricular organ that connects P → C I-comm to brainstem circuits that control homeostasis. We hypothesize that IL-1β and its downstream transcriptional target, cyclooxygenase-2 (COX-2), mediate P → C I-comm in the nTS. In a rodent model of SLI induced by intratracheal bleomycin (Bleo), the sigh frequency and duration of post-sigh apnea increased in Bleo- compared to saline- treated rats one week after injury. This SLI-dependent change in respiratory control occurred concurrently with augmented IL-1β and COX-2 immunoreactivity (IR) in the funiculus separans (FS), a barrier between the AP and the brainstem. At this barrier, increases in IL-1β and COX-2 IR were confined to processes that stained for glial fibrillary acidic protein (GFAP) and that projected basolaterally to the nTS. Further, FS radial-glia did not express TNF-α or IL-6 following SLI. To test our hypothesis, we blocked central COX-1/2 activity by intracerebroventricular (ICV) infusion of Indomethacin (Ind). Continuous ICV Ind treatment prevented Bleo-dependent increases in GFAP + and IL-1β + IR, and restored characteristics of sighs that reset the rhythm. These data indicate that changes in sighs following SLI depend partially on activation of a central COX-dependent P → C I-comm via radial-glia of the FS.
Topics: Animals; Area Postrema; Bleomycin; Communication; Lung Injury; Neuroglia; Rats; Rats, Sprague-Dawley
PubMed: 32097765
DOI: 10.1016/j.bbi.2020.02.006