Effects of a new centrally acting muscle relaxant, NK433 (lanperisone hydrochloride) on spinal reflexes

(-)-(R)-2-methyl-3-(1-pyrrolidinyl)-4'-trifluoromethylpropiophenone++ + monohydrochloride, lanperisone hydrochloride (NK433) administered intravenously or orally depressed the mono- and polysynaptic reflex potential, dorsal root reflex potential, flexor reflex mediated by group II afferent fibers, patellar and flexor reflexes. These effects were reduced by spinal transection. NK433 inhibited the facilitation of the flexor reflex mediated by group II afferent fibers that was induced by intrathecal administration of noradrenaline-HCl. (+)-(1R,2R)-2-methyl-3-(1-pyrrolidinyl)-1-(4-trifluoromethylphenyl)-1-pr opanol (LPS-9)-HCl, a metabolite of NK433, also inhibited the spinal reflexes. Given orally, NK433 had effects more than three times stronger and tending to be longer-lasting than those of eperisone-HCl. These results suggest that NK433 exerts a non-selective inhibition on spinal reflexes and that inhibition of the descending noradrenergic tonic facilitation within the spinal cord is involved in the mechanism of spinal reflex depression by NK433. LPS-9 could contribute to the potent activity of NK433 after oral administration.

Synaptic plasticity of 5-hydroxytryptamine-immunoreactive terminals in the phrenic nucleus following spinal cord injury: a quantitative electron microscopic analysis

The present study was conducted to examine the plasticity of 5-hydroxytryptamine (5-HT)-immunoreactive terminals in the rat phrenic nucleus following an ipsilateral C2 spinal cord hemisection and 30-day survival period. A retrograde horseradish peroxidase (HRP) labeling technique was used to identify the phrenic motoneurons at the electron microscopic (EM) level. After employing a pre-embedding immunocytochemical technique, the ultrastructural characteristics of 5-HT-immunoreactive terminals were qualitatively and then quantitatively analyzed with a computerized morphometric system before and after injury in separate groups of rats. The results indicated that the majority of the 5-HT-labeled terminals formed axodendritic contacts, but some 5-HT-labeled terminals made axosomatic contacts. 5-HT terminals were associated with either asymmetrical or symmetrical synapses, and some displayed postsynaptic dense bodies. Approximately 2% of the 5-HT terminals had dense-core vesicles. Although the total number of labeled and unlabeled terminals in the phrenic nucleus was reduced after hemisection, the number of 5-HT terminals in the hemisected group was greater than that of the control group. Moreover, the total number and length of asymmetrical and symmetrical synaptic active zones per 5-HT terminal were significantly greater after injury. Finally, the total number of 5-HT terminals with multiple synapses was significantly greater in the hemisected group as compared to controls. It is possible that 5-HT synaptic plasticity may be part of the morphological substrate for the unmasking of the latent crossed phrenic pathway which mediates recovery of the ipsilateral hemidiaphragm paralyzed by C2 spinal cord hemisection.

Spinalization increases the mechanical stimulation-induced withdrawal reflex threshold after a sciatic cut in the rat

The purpose of the present study was to establish whether supraspinal structures modulate mechanical 'adjacent hyperalgesia'. After a chronic sciatic cut, the paw withdrawal threshold to mechanical stimulation was lower, and the latency of noxious radiant heat-induced withdrawal reflex was shorter at the traumatized side than at the intact side. Then the rats were spinalized, and the withdrawal threshold to mechanical stimulus increased at the injured side, but the withdrawal latency induced by noxious heat decreased at the intact side. No side differences between the injured and the intact side could be detected after spinalization. Thus supraspinal structures may participate in maintenance of mechanically evoked paw withdrawal reflex after a sciatic injury.

Spinal cord injury and anti-NGF treatment results in changes in CGRP density and distribution in the dorsal horn in the rat

Spinal cord injury (SCI) results in chronic pain states in which the underlying mechanism is poorly understood. To begin to explore possible mechanisms, calcitonin gene-related peptide (CGRP), a neuropeptide confined to fine primary afferent terminals in laminae I and II in the dorsal horn of the spinal cord and implicated in pain transmission, was selected. Immunocytochemical techniques were used to examine the temporal and spatial distribution of CGRP in the spinal cord following T-13 spinal cord hemisection in adult male Sprague-Dawley rats compared to that seen in sham controls. Spinal cords from both hemisected and sham control groups (N = 5, per time point) were examined on postoperative day (POD) 3, 5, 7, 14, and 108 following surgery. Sham operated rats displayed CGRP immunoreaction product in laminae I and II outer, Lissauer's tract, dorsal roots, and motor neurons of the ventral horn. In the hemisected group, densiometric data demonstrated an increased deposition of reaction product that was statistically significant, in laminae III and IV, both ipsilateral and contralateral to the lesion that extended at least two segments rostral and caudal to the hemisection site by POD 14, and remained significantly elevated as long as POD 108. Since upregulation alone of CGRP would occur in an acute temporal window (by 2 to 3 days following spinal injury), these results are interpreted to be invasion of laminae III and IV by sprouting of CGRP containing fine primary afferents. Intrathecal delivery of antibodies against purified 2.5S nerve growth factor for 14 days to the hemisected group resulted in CGRP density in laminae I through IV that was significantly less than that seen in untreated or vehicle treated hemisected groups and to sham controls. These data indicate changes in density and distribution of CGRP following spinal hemisection that can be manipulated by changes in endogenous levels of NGF. These observations suggest possible strategies for intervention in the development of various pain states in human SCI.

Morphological plasticity induced in the phrenic nucleus following cervical cold block of descending respiratory drive

Morphological plasticity occurs in the phrenic nucleus within hours following an ipsilateral C2 spinal cord hemisection. The plasticity has been associated with the unmasking of a latent respiratory pathway (the crossed phrenic pathway) which allows recovery of the hemidiaphragm paralyzed by the hemisection during a reflex known as the crossed phrenic phenomenon. This study tests if the plasticity is induced by the generalized effects of spinal cord trauma or the more specific effect of interrupting the main descending respiratory drive to phrenic motoneurons. Electron microscopic quantitative morphometric analysis of the phrenic nucleus neuropil was carried out on four Sprague-Dawley rats (200-250 g) sacrificed 4 h following unilateral reversible cold block of the descending bulbospinal respiratory drive at the second cervical segment of the spinal cord (C2). The data from four sham-operated control animals were compared with those of the experimental group. The following morphological alterations were documented in cold block animals compared to controls: (1) a significant increase in the number of multiple synapses (i.e., terminals with synaptic active zones contacting two or more postsynaptic profiles in the same plane of section), (2) a significant increase in the number of dendrodendritic appositions, and (3) a significant increase in the length of symmetric and asymmetric synaptic active zones. The above changes are similar to the changes induced in the phrenic nucleus following C2 hemisection. We conclude therefore, that injury to the spinal cord is not a requirement for this type of morphological plasticity in the phrenic nucleus, but rather the induced changes are activity-dependent and are likely caused by the interruption of the descending bulbospinal respiratory drive to the phrenic nucleus.

Responses of the dural circulation to electrical stimulation of the trigeminal ganglion in the cat

1. In cats anaesthetized with alpha-chloralose, electrical stimulation (ES) of the trigeminal ganglion produced a fall in blood pressure, a predominantly ipsilateral dilatation in the common carotid vascular bed and bilateral dilatation of the middle meningeal vascular bed. Section of the trigeminal root abolished these responses. 2. Dilatation in the middle meningeal artery was not affected by section of the cervical sympathetic trunk nor by the section of the seventh cranial nerve trunk. The dilator response was abolished by section of the spinal cord at the C3 level and by intravenous administration of bretylium (10 mg/kg) or phentolamine (5 mg/kg). The response was significantly reduced by the prior administration of papaverine (10 mg/kg). 3. Functional adrenalectomy by means of a snare placed around the nerves and blood vessels supplying the adrenal glands significantly reduced the response. Electrical stimulation of the trigeminal ganglion was accompanied by a fall in circulating levels of noradrenaline and serotonin. 4. We conclude that ES of the trigeminal ganglion produces dilatation in the middle meningeal artery partly by autoregulation during the trigeminal depressor response and partly by a reduction in the circulating levels of noradrenaline. It differs from the dilatation seen in the general carotid circulation and the cortical microcirculation, which is mediated by parasympathetic nerves. There is no evidence that antidromic release of neuropeptides from sensory nerve endings in the dura plays a part in the dilatation.

The superimposed effects of chronic phrenicotomy and cervical spinal cord hemisection on synaptic cytoarchitecture in the rat phrenic nucleus

The present study was carried out to determine the effects of a combined peripheral phrenicotomy and rostral spinal cord hemisection on the synaptic architecture in the ipsilateral rat phrenic nucleus. Young adult female Sprague-Dawley rats were divided into a hemisection-alone and two hemisection-plus-phrenicotomy (HPP) groups. In all animals, DiI, a fluorescent carbocyanine dye was injected into the left hemidiaphragm to retrogradely label the ipsilateral phrenic motoneurons. In the HPP groups, left intrathoracic phrenicotomies were carried out at 2 and 4 weeks prior to sacrificing. Hemisection-alone animals were not subjected to phrenicotomy. In all animals, a left C2 spinal cord hemisection was performed 24 h prior to death. Quantitative morphometric analysis of the phrenic nucleus showed that the number of synapses contacting phrenic profiles is significantly less in the HPP (2 week) group as compared to the hemisection-alone group, but this number returns to a level not significantly different from the hemisection-alone value in the HPP (4 week) group. The results suggest that the transient change in the number of synapses might contribute to the differential expression of the crossed phrenic phenomenon documented in another group of animals subjected to the same surgical procedures. Furthermore, the different stages of glial reaction induced by phrenicotomy/spinal cord hemisection might underlie the change in synaptic number.

A PREPARATION OF THE SPINAL CAT BY AN ANTERIOR APPROACH

A method for preparation of the spinal cat through an anterior approach is described. It has certain advantages over the classical posterior approach and is particularly useful in preparations for studying the superior cervical ganglion or nictitating membrane since the entire procedure may be carried out through the same exposure.

CONTRACTION OF LACTATING RAT MAMMARY GLAND IN RESPONSE TO DIRECT MECHANICAL STIMULATION

Experiments were performed to determine whether the mammary gland myoepithelium of the lactating rat responds to direct mechanical stimulation. Rat pups on postpartum day 14 obtained 8.6 and 12.2% of the total extractable milk in the mammary glands in 31–41 min from anesthetized spinal cord-sectioned and sham-operated mothers, respectively. The mammary glands of both groups responded with a rise in intramammary pressure following mechanical stimulation of the skin overlying the cannulated mammary gland. The responses occurred after a latent period of 1–2 sec, attained an amplitude of 1–13 cm H2O, and lasted 8–18 sec. Summation of the responses did not occur. Temporary fatigue of the response could be induced with repetitive stimuli. Stimulation of mammary glands contralateral to or adjacent to the cannulated gland never produced a response in the cannulated gland. The exposed mammary gland responded to lightly applied mechanical stimulation with alveolar contractions confined to the area of stimulus contact. Each rat responded to intravenous oxytocin (25 mU) with a 10–29 cm H2O intramammary pressure rise of 4–31 min duration.

The origin and significance of spinal cord pulsation

We studied the origin and mechanism of spinal cord pulsation in ten dogs in order to elucidate its clinical significance. Under general anesthesia, a 6 cm length of the animals' cervical spinal cord was exposed and the cerebrospinal fluid removed. The amplitude of spinal pulsation was then measured by means of ultrasonography in Mode M. The measurements were made after the spinal cord was cut: (1) on the cranial side; (2) on the cranial as well as caudal side, with the nerve roots and radicular arteries intact; (3) on both sides as in (2), which was then supplemented with the severance of the nerve roots and radicular arteries. It was demonstrated that, while the pulsation amplitude stood at an average of 88.0 microns before the surgical treatment, it rose to 455.0 microns in (1) and 274.8 microns in (2), but dropped to nearly zero in (3). The 5.2-fold increase in pulsation following the cordotomy on the cranial side was attributed to two factors: (1) the increased spinal mobility due to the cordotomy; (2) the elevation of blood pressure. The results of the three different degrees of spinal detachment suggested that spinal pulsation derived mainly from the radicular arteries and that its presence indicated low tonicity in the spinal cord and favorable circulation in the radicular arteries.

Changes in enzyme histochemical profiles of identified spinal motoneurons of the European eel, Anguilla anguilla, following cordotomy

The enzyme histochemical profiles of glucose-6-phosphate dehydrogenase (a marker of synthetic performance), succinate dehydrogenase (an indicator of oxidative metabolism), and NADH tetrazolium reductase (a marker of overall neuronal activity) were determined for identified white muscle motoneurons in six control and six cordotomized cels. Images were digitized and mean integrated absorbances obtained using appropriate hardware and software. For motoneurons caudal to the transection site there was a significant decrease in the mean absorbance value for NADH tetrazolium reductases which declines from 0.28 a.u. (arbitrary units) in control animals to 0.23 a.u. in cordotomized animals. However, no significant changes were detected in the activities of glucose-6-phosphate and succinate dehydrogenases. The cross-sectional area of the motoneuronal cell body was not affected by cordotomy. The decrease by around 20% in overall neuronal activity, as expressed by NADH tetrazolium reductase activity, might be expected from the decline in body motility that follows cordotomy. Changes in SDH and G6PDH activities would also be expected to follow this surgery, but none were seen, perhaps because they are compensated for by changes in neuronal metabolism that result from deafferentation.

Compulsive targeted self-injurious behaviour in humans with neuropathic pain: a counterpart of animal autotomy? Four case reports and literature review

Four cases of compulsive self-injurious behaviour (SIB) with variable degrees of tissue damage targeted to the painful body part are reported in humans with neuropathic pain. Review of human literature revealed several cases, primarily after central nervous system (CNS) lesions, during which non-psychotic verbally communicating humans (mostly with intact mental status) target specifically the painful part which is usually analgesic or hypoalgesic. In few instances, however, the involved part is not only sentient but also hyperalgesic in part or as a whole. The act is characterized by uncontrollable urge and compulsion, aggravated under conditions of stress, isolation, confusion or depression, and occasionally occurring in patients with personality disorders, ongoing drug abuse and pre-existing compulsive habits (i.e., habitual nail biting or picking). It fails to be deterred by the appearance of the injured part, social mores or even the experience of pain. Successful treatment of underlying painful dysesthesiae with specific medications, neurostimulation or surgery has resulted in marked improvement of dysesthesiae accompanied by wound healing in several cases. The four presented cases and the human literature experience provide evidence that compulsive targeted SIB in humans with neuropathic pain and painful dysesthesiae is consistent with the concept that animal autotomy may result from chronic neuropathic pain after experimental peripheral or CNS lesions.

Amantadine stimulates sexual behavior in male rats

The effects of amantadine on sexual behavior, penile erection, and seminal emission of male rats was studied. Amantadine significantly decreased latency of mounts in all doses (1.25 to 50 mg/kg), and decreased the number of mounts and intromission latency at the highest doses used. The lowest dose of amantadine significantly increased ejaculation latency and intromission frequency, while higher doses significantly reduced it, which indicates a biphasic response of the drug. Additionally, seminal emission, erections, and genital grooming were significantly induced by amantadine. Amantadine-induced seminal emissions were impaired by spinal cord transection, which suggests the involvement of supraspinal structures in the drug action. Haloperidol and atropine sulphate significantly reduced seminal emissions and penile erections induced by amantadine. These results demonstrate that amantadine stimulates sexual behavior and genital reflexes in male rats and suggest a facilitatory effect of the drug that probably involves different mechanisms of action.

Selective antinociceptive effect of excitatory amino acid antagonists in intact and acute spinal rats

Results of neurophysiologic and behavioral studies suggest that excitatory amino acid (EAA) antagonists may provide a new class of analgesic agents, which might be selective for neuropathic pain states that are resistant to opiate treatment. Most of these paradigms involve animal models of peripheral injury. The present study evaluated the antinociceptive effect of spinally [intrathecally (IT)] administered EAA antagonists after central injury, produced by spinal transection. Intrathecal injection of the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione produced dose-dependent antinociception on the thermal tail withdrawal [tail-flick (TF)] reflex test in Intact rats, which was significantly potentiated after spinal transection. In contrast, IT injection of the NMDA antagonist, 2-amino-5-phosphonopentanoic acid (AP5) did not affect the TF in intact rats, but significantly blocked this response in spinal rats. However, some of the spinal rats did not recover the reflex, suggesting a possible toxic action of AP5.

Effects of astrocyte implantation into the hemisected adult rat spinal cord

Morphological and biochemical methods were applied to assess the effects of implanting cultured astrocytes into the hemisected adult rat spinal cord. Astrocytes were purified from neonatal rat cortex and introduced into the lesioned spinal cord either in suspension injection or cultured on gelfoam first. The control groups were rats which had hemisection with injection of culture media or with gelfoam grafted alone. At various time points after surgery (two weeks to two months), the spinal cord was removed and processed for routine light microscopy, immunofluorescence, gel electrophoresis and immunoblotting. As early as two weeks after surgery, a significantly smaller volume of scar tissue was consistently found in the experimental groups. This reduced scarring was also confirmed by immunofluorescence staining and immunoblotting for glial fibrillary acidic protein in the specimens two months after hemisection. Compared to the control groups, the experimental groups also had more intense staining for neurofilaments, which was confirmed by immunoblotting. However, labelling of the astrocytes with Phaseolus vulgaris leucoagglutinin conjugated with fluorescein showed that the astrocytes migrated at a rate of 0.6 mm/day from the original implanted site. The results therefore suggested that the cultured astrocytes probably exerted their effects over a short time period (less than two weeks) around the lesion site. They could have altered the microenvironment and as a result less scar tissue was formed. Hence, there was less barrier to the regrowth of nerve fibres.

Substance P is a possible neurotransmitter in the rat spinothalamic tract

In order to shed some light on the neurotransmitters in the spinothalamic tract (STT), we examined, biochemically and immunohistochemically, the contents of various neurotransmitter candidates in the terminal field of the STT after cervical hemi-chordotomy (HC) and dorsal quadrant-chordotomy (dQC) in the rat. Substance P (SP), calcitonin gene-related peptide (CGRP), enkephalin, neuropeptide Y, neurotensin, oxytocin and dynorphin A were analyzed immunohistochemically. The contents of neuropeptides (SP, CGRP and cholecystokinin octapeptide) were measured by radioimmunoassay and those of amino acids (aspartic acid, glutamic acid, gamma-aminobutyric acid (GABA) and glycine) and noradrenaline were determined using high-performance liquid chromatography. Cervical hemi-chordotomy, but not dQC, caused significant decreases of the SP-like immunoreactivity in and SP content of the ventral thalamus on the ipsilateral side, compared with that on the contralateral side and of rats subjected to sham-operation. However, neither HC nor dQC resulted in any changes in the ventral thalamic contents of other putative neurotransmitters examined. These results suggest that, in rats, the STT contains SP and that SP-positive fibers run in the ventral half of the ascending spinal tract at the cervical level.

The antinociceptive action of an alpha 2-adrenoceptor agonist in the spinal dorsal horn is due to a direct spinal action and not to activation of descending inhibition

In this electrophysiological study we tried to find out whether the spinal antinociceptive effect of a supraspinally administered alpha 2-adrenoceptor agonist is due to a direct spinal effect or to activation of descending inhibition. The responses to wide-dynamic range (WDR) neurons of the spinal dorsal horn were studied following application of medetomidine, a selective alpha 2-adrenergic agonist, into the rostroventromedial medulla (RVM) or directly onto the spinal cord of the intact and in spinal rats. The noxious electrical stimuli were applied to the ipsilateral receptive field in the plantar region of the hind paw, and responses mediated by A- and C-fibers to WDR neurons were separately evaluated. The reversal of medetomidine-induced effects was attempted by a systemic administration of atipamezole, a selective alpha 2-adrenoceptor antagonist. Medetomidine injection into the RVM produced a dose-dependent, atipamezole-reversible attenuation of the C-fiber-mediated responses to WDR neurons of the spinal dorsal horn in both intact and spinal rats. Paradoxically, the spinal antinociceptive effect of supraspinally administered medetomidine was stronger in spinal rats. The A-fiber-mediated responses were significantly less attenuated by medetomidine than the C-fiber-mediated responses to the WDR neurons. Also a direct application of medetomidine onto the spinal cord produced a dose-dependent, atipamezole-reversible attenuation of the C-fiber-mediated responses, and this effect was identical in intact and in spinal rats. The medetomidine doses producing spinal antinociception were considerably lower with a direct spinal application than with a supraspinal application.(ABSTRACT TRUNCATED AT 250 WORDS)

Normal distribution of alpha 2-adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: a quantitative autoradiographic study

The distribution of alpha 2 (alpha 2)-adrenoceptors along cervical, thoracic, lumbar, and sacral segments of the spinal cord of normal rats has been studied by quantitative autoradiography using the specific alpha 2-antagonist [3H]rauwolscine as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8-T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6-hydroxydopamine (6-OHDA)] on eventual variations of alpha 2-adrenoceptor density at spinal cord target cells was studied in parallel. In control rats, the quantitative analysis of alpha 2-adrenoceptor densities revealed the presence of these receptors throughout the whole gray matter with a preferential location in the superficial dorsal horn. This pattern was the same at all rostro-caudal levels of the cord and appeared very well correlated with the distribution of NA terminals revealed by immunohistochemistry, particularly in the superficial layers of the dorsal horn. After total transection of the spinal cord (caudally to the section) and 6-OHDA-induced lesion, an increase of alpha 2-adrenoceptor density was mainly observed within the distal dorsal horn thus evidencing supersensitivity in this area, while modifications were not detectable in other regions of the spinal gray matter, except at the lumbar level where other dorsal, central, and intermediate zones were significantly enriched.

Percutaneous cervical cordotomy and subarachnoid phenol block using fluoroscopy in pain control of costopleural syndrome

We examined the efficacy of percutaneous cervical cordotomy (PCC) and subarachnoid phenol block using fluoroscopy (SAPB-F) for control of chest and/or back pain from costopleural syndrome. The efficacy of each block was evaluated by changes in pain score (PS), analgesic dose and performance status 1 week after the block, as well as by the complications. Between 1980 and 1986, PCC was performed in 10 patients. SAPB-F was performed in 13 patients between 1987 and 1991. Pain was not well controlled by analgesics in any of these patients. For PCC the follow-up period was 94.7 +/- 71.1 days. PS (VAS, 0-10) reduced from 8.5 +/- 0.9 to 3.0 +/- 2.7. No analgesics were needed in 4 patients. Pain recurred in 1 patient. Hemiparesis occurred in 2 patients. General fatigue occurred in 6 patients. In 4 patients with these complications performance status deteriorated and did not recover during the follow-up period. For SAPB-F the follow-up period was 71.8 +/- 44.0 days. SAPB-F was designed to achieve selective phenol deposit at the targeted nerve root. PS decreased from 7.5 +/- 1.9 to 2.7 +/- 2.6. No analgesics were needed in 5 patients. Pain recurred in 3 patients. There were no complications and no changes in performance status. From this study we concluded that PCC is an effective method of pain control for costopleural syndrome, but a risk of serious complications is involved. SAPB-F is an effective and safe method and should be the first choice of nociceptive pathway block.

Course of spinocerebellar axons in the ventral and lateral funiculi of the spinal cord with projections to the anterior lobe: an experimental anatomical study in the cat with retrograde tracing techniques

The fiber course of the spinocerebellar tracts in the ventral and lateral funiculi of the cat spinal cord were studied by a new approach, making cordotomies at different spinal levels or lesions of the restiform body followed by injections of HRP or WGA-HRP into the anterior cerebellar lobe. The retrogradely labeled axons showed characteristic distribution patterns related to the level and extent of the lesions. The results show the following. 1) The dorsal spinocerebellar tract (DSCT) originating ipsilaterally from the thoracic and upper lumbar segments ascends in the dorsolateral fasciculus. It undergoes a dorsal shift during its rostral course. The tract is topically arranged and passes through the restiform body. 2) The ventral spinocerebellar tract (VSCT) arising contralaterally from lower thoracic, lumbar, and more caudal segments passes via the ventral funiculus and ascends in the ventrolateral fasciculus. This tract is also topically arranged. It makes a lateral and then a dorsal shift during its ascending course. The main portion of the VSCT enters the cerebellum via the superior cerebellar peduncle. A minor portion originating from the sacrococcygeal region enters via the restiform body. 3) The spinocerebellar fibers originating ipsilaterally from the cervical enlargement ascend in the lateralmost part of the lateral funiculus in the area between the dorsolateral and ventrolateral fasciculi. These fibers form two groups, one passing through the restiform body, the other through the superior cerebellar peduncle. 4) The spinocerebellar fibers originating contralaterally from the central cervical nucleus pass through the ventral funiculus and ascend in the lateralmost part of the lateral funiculus, mainly in the ventrolateral fasciculus. Most of the fibers seem to pass through the superior cerebellar peduncle.

Axonal sprouting in the hemisected adult rat spinal cord

The morphological and biochemical changes were studied in adult Sprague-Dawley rats after hemisection at the L3 spinal cord level. After survival periods of one, two and three months, fluorescent tracers, FluoroGold or rhodamine B, were implanted into the dorsal white columns of these rats at the positions of the corticospinal tract below the lesion. Following uptake of the tracer, the rats were killed and the motor cortices and spinal cords of both control and hemisected rats were analysed for positively labelled neurons. The highest number of labelled cells were found two months after hemisection. They were present in both sides of the cortices, particularly in the contralateral cortex, and also in the gray matter of the spinal cord above the hemisection. A few rats which were subjected to complete transection of the spinal cord also showed labelling of neurons in the motor cortex two months after lesion. The Protargol silver technique and the [3H]choline uptake study confirmed the presence of nerve fibres traversing the lesion site in the hemisected spinal cord. Furthermore, when the rats that had been hemisected two months earlier were subjected to a second cut at the same site, chromatolytic neurons were observed in the spinal cord as well as in the motor cortices of both sides. The hemisected rats demonstrated limited recovery in limb movement. The evidence of this study clearly shows that sprouting of nerve fibres has occurred in the lesioned adult rat spinal cord.