Showing papers on "Cuneate nucleus published in 1997"
TL;DR: The results show that injury of nerves to the hands of adult monkeys triggers rapid changes in maps of the hand in the brainstem main cuneate nucleus, and suggest that peripheral injury causes an initial concurrent reorganization of brainstem and cortical substrates.
49 citations
TL;DR: Results indicate that capsaicin-sensitive primary afferents and brain CRF receptors are part of the pathways and biochemical coding through which abdominal surgery activates PVN neurons 1 h post surgery.
47 citations
TL;DR: In adult monkeys with dorsal rhizotomies extending from the second cervical (C2) to the fifth thoracic (T5) vertebrae, cortex deprived of its normal inputs regained responsiveness to inputs conveyed by intact peripheral afferents from the face, suggesting reorganizational limits in adult primate somatosensory cortex.
44 citations
TL;DR: This experiment demonstrates that reorganization in the adult somatotopic system does occur at the level of the dorsal column nuclei and indicates that there is a strengthening of synapses that were previously ineffective in the somatosensory pathway.
Abstract: Rasmusson, Douglas D. and Stacey A. Northgrave. Reorganization of the raccoon cuneate nucleus after peripheral denervation. J. Neurophysiol. 78: 2924–2936, 1997. The effects of peripheral nerve tra...
43 citations
TL;DR: Results indicate that hindlimb input to the portion of SI representing the Forelimb stump is functionally suppressed in rats that have sustained neonatal forelimb removal and that GABAergic inhibition, mediated by both GABA(A) and GABA(B) receptors, is involved in this process.
Abstract: A previous study from this laboratory demonstrated that forelimb removal at birth results in invasion of the cuneate nucleus (CN) by sciatic nerve axons and the development of CN cells including thalamic projection neurons with receptive fields that include both the forelimb stump and the hindlimb. However, recordings from unit clusters in lamina IV of the primary somatosensory cortex (SI) of these animals revealed the presence of only a very few sites in the forelimb stump representation where responses to hindlimb stimulation could also be recorded. In the present study we tested the possibility that input from the hindlimb was suppressed in lamina IV of the cortical stump representation via GABAergic inhibitory mechanisms by mapping this cortical region, applying the gamma-aminobutyric acid-A (GABA(A)) and GABA(B) receptor antagonists bicuculline and phaclofen (50 microM each), and then remapping the same sites. In six neonatally manipulated rats, 15 of 242 sites (6.2%) in the stump representation responded to hindlimb stimulation before GABA receptor blockade and 107 (44.2%) of the same sites responded to stimulation of the hindlimb during blockade (P 0.05). These results indicate that hindlimb input to the portion of SI representing the forelimb stump is functionally suppressed in rats that have sustained neonatal forelimb removal and that GABAergic inhibition, mediated by both GABA(A) and GABA(B) receptors, is involved in this process.
35 citations
TL;DR: Results indicate that SHT axons ascend toward the hypothalamus in a clearly circumscribed projection in the lateral brain stem and posterior thalamus and appears to be capable of providing nociceptive input to many areas that are involved in the production of multifaceted responses to noxious stimuli.
Abstract: Antidromic activation was used to determine the locations of ascending spinohypothalamic tract (SHT) axons and their collateral projections within C1, medulla, pons, midbrain, and caudal thalamus. Sixty-four neurons in the cervical enlargement were antidromically activated initially by stimulation within the contralateral hypothalamus. All but one of the examined SHT neurons responded either preferentially or specifically to noxious mechanical stimuli. A total of 239 low-threshold points was classified as originating from 64 ascending (or parent) SHT axons. Within C1, 38 ascending SHT axons were antidromically activated. These were located primarily in the dorsal half of the lateral funiculus. Within the medulla, the 29 examined ascending SHT axons were located ventrolaterally, within or adjacent to the lateral reticular nucleus or nucleus ambiguus. Within the pons, the 25 examined ascending SHT axons were located primarily surrounding the facial nucleus and the superior olivary complex. Within the caudal midbrain, the 23 examined SHT ascending axons coursed dorsally in a position adjacent to the lateral lemniscus. Within the anterior midbrain, SHT axons traveled rostrally near the brachium of the inferior colliculus. Within the posterior thalamus, all 17 examined SHT axons coursed rostrally through the posterior nucleus of thalamus. A total of 114 low-threshold points was classified as collateral branch points. Sixteen collateral branches were seen in C1; these were located primarily int he deep dorsal horn. Forty-five collateral branches were located in the medulla. These were primarily in or near the medullary reticular nucleus, nucleus ambiguus, lateral reticular nucleus, parvocellular reticular nucleus, gigantocellular reticular nucleus, cuneate nucleus, and the nucleus of the solitary tract. Twentysix collateral branches from SHT axons were located in the pons. These were in the pontine reticular nucleus caudalis, gigantocellular reticular nucleus, parvocellular reticular nucleus, and superior olivary complex. Twenty-three collateral branches were located in the midbrain. These were in or near the mesencephalic reticular nucleus, brachium of the inferior colliculus, cuneiform nucleus, superior colliculus, central gray, and substantia nigra. Int he caudal thalamus, two branches were in the posterior thalamic nucleus and two were in the medial geniculate. These results indicate that SHT axons ascend toward the hypothalamus in a clearly circumscribed projection in the lateral brain stem and posterior thalamus. In addition, large numbers of collaterals from SHT axons appears to project to a variety of targets in C1, the medulla, pons, midbrain, and caudal thalamus. Through its widespread collateral projections, the SHT appears to be capable of providing nociceptive input to many areas that are involved in the production of multifaceted responses to noxious stimuli.
32 citations
TL;DR: It was demonstrated that the GABA-immunoreactive neurons in the rat cuneate nucleus were post-synaptic to PATs, GABA-IR and GABA-negative terminals, and it was suggested that the PATs and glutamate-IR terminals on GABA-ir neurons may be involved in lateral inhibition for increase of spatial precision.
29 citations
TL;DR: The present results suggest that cortical modulation on the sensory transmission of cuneate nucleus may be mediated through glycine-IR neurons.
22 citations
TL;DR: It is suggested from this study that glycine is one of the major neurotransmitters involved in the depression of synaptic transmission in the cuneate nucleus.
Abstract: The distribution of glycine-immunoreactive (glycine-IR) neurons and their associated axon terminals in the rat cuneate nucleus was studied using antiglycine postembedding immunoperoxidase labelling and immunogold staining, respectively. The immunoperoxidase-labelled glycine-IR neurons were widely distributed in the entire rostrocaudal extent of the nucleus. They made up 30.8% (9671/31368) of the neurons surveyed. Quantitative evaluation showed that the percentage of glycine-IR neurons in the caudal level was significantly higher than that in the middle and rostral levels. The glycine-IR neurons were small cells (mean area=198±1.9 μm2, n=2862) with ovoid or spindle-shaped somata. Statistical analysis showed that the size of the glycine-IR neurons in the rostral level was significantly smaller than that in the middle and caudal levels. Immunogold labelled glycine-IR terminals which contained predominantly pleomorphic synaptic vesicles were mostly small (mean area=1.24±0.03 μm2, n=286) and they constituted 24.7% (286/1158) of the total terminals surveyed. They formed axodendritic, axosomatic and axoaxonic synapses with unlabelled elements. It is suggested from this study that glycine is one of the major neurotransmitters involved in the depression of synaptic transmission in the cuneate nucleus.
12 citations
TL;DR: Results in the primate confirm earlier results in the cat that transection and microsurgical repair of a sensory nerve causes a considerable loss of neurons capable of intraaxonal transport.
Abstract: In order to investigate the changes in the somatosensory organization that occur after a peripheral nerve injury, a purely sensory nerve (radial nerve – superficial branch) was divided in adult monkeys (Macaca fascicularis). The nerve ends were immediately rejoined by an epineural suturing technique. After 6–21 months the nerve investigated was exposed to an intra-axonal nerve tracer (horseradish peroxidase conjugate) in order to label the primary afferent terminals within the cuneate nucleus of the brainstem. The non-transected nerve on the contralateral side was similarly exposed and served as a control. Terminal labelling was seen throughout the cuneate nucleus, mainly in the middle of its rostro-caudal extension, and in this part it showed a patchy appearance superimposed on cell clusters within the pars rotunda. This pattern of distribution was seen both on the experimental and control sides. On the experimental side there was an obvious loss of terminal labelling within the terminal field as estimated using an image-analysing system: Compared with the contralateral side the median loss (peroxidase activity) was 83% and between 6 and 21 months only minor restoration of the terminal intensity was observed. These results in the primate confirm earlier results in the cat that transection and microsurgical repair of a sensory nerve causes a considerable loss of neurons capable of intraaxonal transport.
9 citations
TL;DR: The results indicate that cuneate neurones can acquire normal tactile coding capacities despite the disruption caused by prior crush injury to their peripheral nerve source.
Abstract: 1. The capacity of cuneate neurones to attain normal functional properties following neonatal median nerve injury was investigated with single neurone recording in anaesthetized cats, 12-24 months subsequent to a controlled crush injury. Effectiveness of the peripheral nerve injury was confirmed by the abolition of the median nerve compound action potential following the crush. 2. Cuneate recording was carried out after denervation of the forearm, apart from the median nerve, to ensure that neurones studied had receptive fields within the distribution zone of the regenerated median nerve. Controlled and reproducible tactile stimuli were used to evaluate the functional capacities of neurones to determine whether they were consistent with those reported earlier for cuneate neurones in cats that had normal peripheral nerve development. 3. Twenty-two cuneate neurones with well-defined tactile receptive fields within the distribution zone of the regenerated median nerve were classified according to their adaptation characteristics and functional properties. Slowly adapting neurones responded throughout static skin indentations and had graded and approximately linear stimulus-response relations over indentation ranges up to 1.5 mm. Rapidly adapting neurones responded to the dynamic phases of skin indentations and could be divided into two broad classes, one most sensitive to vibrotactile stimuli at 200-400 Hz which appeared to receive a predominant input from Pacinian corpuscle receptors, and a non-Pacinian group that included neurones most sensitive to skin vibration at 5-50 Hz which appeared to receive glabrous skin input from the rapidly adapting class of afferent fibres. 4. Based on the stimulus-response relations and on measures of phase locking in the responses to vibrotactile stimuli, it appears that the functional properties of cuneate neurones activated from the field of a regenerated median nerve subsequent to a neonatal nerve crush injury were consistent with those reported previously for 'control' cuneate neurones. The results indicate that cuneate neurones can acquire normal tactile coding capacities despite the disruption caused by prior crush injury to their peripheral nerve source.
TL;DR: The immunohistochemical study revealed a lot of substance P-immunoreactive neurons in the geniculate and jugular ganglia, and heavy accumulation of immunoreactive fibers in laminae I-II of the upper cervical spinal cord.
Abstract: Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) injection into the facial nerve of the cat resulted in retrograde labeling in the geniculate and jugular ganglia ipsilaterally. Labeled fibers were found to enter into the brain stem through the intermediate and vagal nerves. These fibers ascended or descended into the dorsal portion of the spinal trigeminal tract and were distributed to the principal sensory nucleus of the trigeminal nerve, marginal layer of the interpolar part of the spinal trigeminal nucleus, nucleus of the solitary tract and ventrolateral portion of the cuneate nucleus. It was of particular interest in the present study that the intensive labeling was present in the medial portion of laminae I-IV of the upper cervical spinal cord. The immunohistochemical study revealed a lot of substance P-immunoreactive neurons in the geniculate and jugular ganglia, and heavy accumulation of immunoreactive fibers in laminae I-II of the upper cervical spinal cord.
TL;DR: It is demonstrated that neurons in the dorsal column nuclei express preprocholecystokinin messenger RNA, and show that these neurons provide a peptidergic projection from the dorsalcolumn nuclei to the ventroposterolateral nucleus of the thalamus.