Effect of Midthoracic Spinal Cord Constriction on Catalytic Nitric Oxide Synthase Activity in the White Matter Columns of Rabbit

The distribution and changes of catalytic nitric oxid synthase (cNOS) activity in the dorsal, lateral and ventral white matter columns at midthoracic level of the rabbit's spinal cord were studied in a model of surgically-induced spinal cord constriction performed at Th7 segment level and compared with the occurrence of nicotinamide adenine dinucleotide phosphate diaphorase expressing and neuronal nitric oxide synthase immunoreactive axons in the white matter of the control thoracic segments. Segmental and white-column dependent differences of cNOS activity were found in the dorsal (141.5 ± 4.2 dpm/m protein), lateral (87.3 ± 11.5 dpm/m protein) and ventral (117.1 ± 7.6 dpm/m protein) white matter columns in the Th5-Th6 segments and in the dorsal (103.3 ± 15.5 dpm/m protein), lateral (54.9 ± 4.9 dpm/m protein), and ventral (86.1 ± 6.8 dpm/m protein) white matter columns in the Th8-Th9 segments. A surgically-induced constriction of Th7 segment caused a disproportionate response of cNOS activity in the rostrally (Th5-Th6) and caudally (Th8-Th9) located segments in both lateral and ventral white matter columns. While a statistically significant decrease of cNOS activity was detected above the constriction site in the ventral columns, a considerable, statistically significant increase of cNOS activity was noted in the white lateral columns below the site of constriction. It is reasoned that the changes of cNOS activity may have adverse effects on nitric oxide (NO) production in the white matter close to the site of constriction injury, thus broadening the scope of the secondary mechanisms that play a role in neuronal trauma.     

Regional Changes of Cyclic 3′,5′-Guanosine Monophosphate in the Spinal Cord of the Rabbit following Brief Repeated Ischemic Insults

The regional distribution of cyclic 3,5-guanosine monophosphate was studied in the lumbosacral segments of the spinal cord of the rabbit under physiological conditions and following brief repeated sublethal ischemic insults. While the basal cGMP level in the gray matter was about 0.120 nmol cGMP/mg wet. wt., the level of cGMP in non-compartmentalized white matter was about half of this value. The highest level of cGMP in the compartmentalized gray matter was found in the dorsal horns, about 0.180 nmol cGMP/mg wet. wt., whereas the level of cGMP was greatly reduced in the ventral horns, reaching one half of the previous value. Multiple sublethal ischemic insults, repeated at 1-h intervals, caused a statistically significant decrease of cGMP in all gray matter regions. While the post-ischemic and post-reperfusion level of cGMP in the dorsal horns remained relatively high in comparison with the intermediate zone and ventral horns, the changes of cGMP level detected in the white matter columns differed considerably and resulted in a statistically significant cGMP increase in the dorsal and ventral columns and, vice versa, a statistically significant decrease of cGMP was found in the lateral columns.     

The Effect of Cauda Equina Constriction on Nitric Oxide Synthase Activity

Nitric oxide synthase (NOS) activity was studied in the gray and white matter regions of the spinal cord 2 and 5 days after multiple cauda equina constrictions of the central processes of L7-Co5 dorsal root ganglia neurons. The results show considerable differences in enzyme activity in the thoracic, upper lumbar, lower lumbar, and sacral segments. Increased NOS activity was observed at 2 days after multiple cauda equina constrictions in the dorsal, lateral, and ventral columns of the lower lumbar segments and in the ventral column of the upper lumbar segments. The values returned to control levels within 5 postconstriction days. In the lateral columns of thoracic segments taken 2 and 5 days after surgery, NOS activity was enhanced by 54% and 55% and in the upper lumbar segments by 130% and 163%, respectively. Multiple cauda equina constrictions performed surgically for 2 and 5 days caused a significant increase in NOS activity predominantly in the gray matter regions of thoracic segments. A quite different response was found 5 days postconstriction in the upper lumbar segments, where the enzyme activity was significantly decreased in the dorsal horn, intermediate zone, and ventral horn. No such extreme differences could be seen in the lower lumbar segments, where NOS activity was significantly enhanced only in the ventral horn. The data correspond with a higher number of NOS immunoreactive somata, quantitatively evaluated in the ventral horn of the lower lumbar segments at 5 days after multiple cauda equina constrictions. While the great region-dependent heterogeneity in NOS activity seen 2 and 5 days after multiple cauda equina constrictions is quite apparent and suggestive of an active role played by nitric oxide in neuroprotective or neurotoxic processes occurring in the gray and white matter of the spinal cord, the extent of damage or the degree of neuroprotection caused by nitric oxide in compartmentalized gray and white matter in this experimental paradigm would be possible only using longer postconstriction periods.     

Alterations in growth-associated protein (GAP-43) expression in lower urinary tract pathways following chronic spinal cord injury

Alterations in the expression of growth-associated protein 43 (GAP-43) were examined in lower urinary tract micturition reflex pathways 6 or 8 weeks following complete spinal cord transection (~ T9). In control animals, expression of GAP-43 was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure; (2) the corticospinal tract; (3) the dorsal horn; and (4) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (L6-S1); and (5) in the lateral collateral pathway of Lissauer in L6-S1 spinal segments. Densitometry analysis has demonstrated significant increases (p 0.001; 1.3-6.4-fold increase) in GAP-43-immunoreactivity (IR) in these regions of the rostral lumbar (L1-L2) and caudal lumbosacral (L6-S1) spinal cord 6 weeks following spinal cord injury. Changes in GAP-43-IR were restricted to the L1-L2 and L6-S1 segments that are involved in lower urinary tract reflexes. Changes in GAP-43-IR were not observed at the L5 segmental level except for an increase in GAP-43-IR in the superficial, dorsal horn at 6 weeks post-injury. In all segments examined, GAP-43-IR was decreased (2-5-fold) in the corticospinal tract (dorsal division) 6 and 8 weeks following spinal cord injury. Eight weeks following spinal cord injury, changes in GAP-43-IR had returned to control levels except for the persistence of increased GAP-43-IR in the region of the sacral parasympathetic nucleus and the lateral collateral pathway in the S1 spinal segment. Alterations in GAP-43-IR following chronic spinal cord injury may suggest a reorganization of bladder afferent projections and spinal elements involved in urinary bladder reflexes consistent with alterations in urinary bladder function (hyperreflexia) observed in animals following spinal cord injury above the lumbosacral spinal cord.     

Alterations in growth-associated protein (GAP-43) expression in lower urinary tract pathways following chronic spinal cord injury

Alterations in the expression of growth-associated protein 43 (GAP-43) were examined in lower urinary tract micturition reflex pathways 6 or 8 weeks following complete spinal cord transection (approximately T9). In control animals, expression of GAP-43 was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure; (2) the corticospinal tract; (3) the dorsal horn; and (4) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (L6-S1); and (5) in the lateral collateral pathway of Lissauer in L6-S1 spinal segments. Densitometry analysis has demonstrated significant increases (p < or =0.001; 1.3-6.4-fold increase) in GAP-43-immunoreactivity (IR) in these regions of the rostral lumbar (L1-L2) and caudal lumbosacral (L6-S1) spinal cord 6 weeks following spinal cord injury. Changes in GAP-43-IR were restricted to the L1-L2 and L6-S1 segments that are involved in lower urinary tract reflexes. Changes in GAP-43-IR were not observed at the L5 segmental level except for an increase in GAP-43-IR in the superficial, dorsal horn at 6 weeks post-injury. In all segments examined, GAP-43-IR was decreased (2-5-fold) in the corticospinal tract (dorsal division) 6 and 8 weeks following spinal cord injury. Eight weeks following spinal cord injury, changes in GAP-43-IR had returned to control levels except for the persistence of increased GAP-43-IR in the region of the sacral parasympathetic nucleus and the lateral collateral pathway in the S1 spinal segment. Alterations in GAP-43-IR following chronic spinal cord injury may suggest a reorganization of bladder afferent projections and spinal elements involved in urinary bladder reflexes consistent with alterations in urinary bladder function (hyperreflexia) observed in animals following spinal cord injury above the lumbosacral spinal cord.     

The Effect of a Spinal Cord Hemisection on Changes in Nitric Oxide Synthase Pools in the Site of Injury and in Regions Located Far Away from the Injured Site

1. The present study was designed to examine the nitric oxide synthase activities (constitutive and inducible) in the site of injury in response to Th10-Th11 spinal cord hemisection and, to determine whether unilateral disconnection of the spinal cord influences the NOS pools on the contra- and ipsilateral sides in segments located far away from the epicentre of injury.2. A radioassay detection was used to determine Ca²⁺-dependent and inducible nitric oxide synthase activities. Somal, axonal and neuropil neuronal nitric oxide synthase was assessed by immunocytochemical study. A quantitative assessment of neuronal nitric oxide synthase immunoreactivity was made by an image analyser. The level of neuronal nitric oxide synthase protein was measured by the Western blot analysis.3. Our data show the increase of inducible nitric oxide synthase activity and a decrease of Ca²⁺-dependent nitric oxide synthase activity in the injured site analysed 1 and 7 days after surgery. In segments remote from the epicentre of injury the inducible nitric oxide synthase activity was increased at both time points. Ca²⁺-dependent nitric oxide synthase activity had decreased in L5-S1 segments in a group of animals surviving for 7 days. A hemisection performed at thoracic level did not cause significant difference in the nitric oxide synthase activities and in the level of neuronal nitric oxide synthase protein between the contra- and ipsilateral sides in C6-Th1 and L5-S1 segments taken as a whole. Significant differences were observed, but only when the spinal cord was analysed segment by segment, and/or was divided into dorsal and ventral parts. The cell counts in the cervicothoracic (C7-Th1) and lumbosacral (L5-S1) enlargements revealed changes in neuronal nitric oxide synthase immunoreactivity on the ipsilateral side of the injury. The densitometric area measurements confirmed the reduction of somal, neuropil and axonal neuronal nitric oxide synthase immunoreactive staining in the ventral part of rostrally oriented segments.4. Our findings provide evidence that the changes in nitric oxide synthase pools are limited not only to impact zone, but spread outside the original lesion. The regional distribution of nitric oxide synthase activity and neuronal nitric oxide synthase immunoreactivity, measured segment by segment shows that nitric oxide may play a significant role in the stepping cycle in the quadrupeds.     

Localization and distribution patterns of nicotinamide adenine dinucleotide phosphate diaphorase exhibiting axons in the white matter of the spinal cord of the rabbit

The funicular distribution of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)-exhibiting axons was examined in the white matter of the rabbit spinal cord by using horizontal, parasaggital, and transverse sections. Four morphologically distinct kinds of NADPHd-exhibiting axons (2.5–3.5 m in diameter) were identified in the sulcomarginal fasciculus as a part of the ventral column in the cervical and upper thoracic segments and in the long propriospinal bundle of the ventral column in Th3–L3 segments. Varicose NADPHd-exhibiting axons of the sympathetic preganglionic neurons, characterized by widely spaced varicosities, were found in the ventral column of Th2–L3 segments. A third kind of NADPHd-positive ultrafine axons, 0.3–0.5 m in diameter with numerous varicosities mostly spherical in shape, was identified in large number within Lissauer's tract. The last group of NADPHd-exhibiting axons (1.0–1.5 m in diameter) occurred in the Lissauer tract. Most of these axons were traceable for considerable distances and generated varicosities varying in shape from spherical to elliptical forms. The majority of NADPHd-exhibiting axons identified in the cuneate and gracile fascicles were concentrated in the deep portion of the dorsal column. An extremely reduced number of NADPHd-exhibiting axons, confirmed by a computer-assisted image-processing system, was found in the dorsal half of the gracile fascicle. Axonal NADPHd positivity could not be detected in a wide area of the lateral column consistent with the location of the dorsal spinocerebellar tract. Numerous, mostly thin NADPHd-positive axonal profiles were detected in the dorsolateral funiculus in all the segments studied and in a juxtagriseal portion of the lateral column as far as the cervical and lumbar enlargements. A massive occurrence of axonal NADPHd positivity was detected in the juxtagriseal layer of the ventral column all along the rostrocaudal axis of the spinal cord. The prominent NADPHd-exhibiting bundles containing thick, smooth, nonvaricose axons were identified in the mediobasal and central portion of the ventral column. First, the sulcomarginal fasciculus was found in the basal and medial portion of the ventral column in all cervical and upper thoracic segments. Second, more caudally, a long propriospinal bundle displaying prominent NADPHd positivity was localized in the central portion of the ventral column throughout the Th3–L3 segments.     

Ponto-medullary projections to the spinal cord: a quantitative study in the cat

The purpose of this research has been to study quantitatively the ponto-medullary projections to the lateral and ventral funiculi in both cervical (C3) and thoracic (Th8) levels. The method consisted in the partial interruption of the spinal cord, sparing one funiculus in which 5-30 microliter of HRP 30% solution was injected at about 1 cm caudally. 19 cats were utilized, 12 for cervical (6 for lateral and 6 for ventral funiculus) and 7 for lumbar injection (3 for lateral and 4 for ventral funiculus). The structures which project to both funiculi of spinal cord (RM, RL, Poo, PR at Th8 level; RM, RL, Poo at C3 level) could exert integrative effects on the proximal and distal segments of the limbs. The structures which project only to FV (VL and Poc at Th8 level; VL, VIN and Poc at C3 level) or to FL (LSC at Th8; PR at C3) could be implied in motor control of only the proximal or distal regions.     

白鱀豚脊髓的解剖学和组织学研究

采用２头白豚的脊髓分别做成浸制标本和切片。其脊髓式为Ｃ＿Ｒ－Ｔ＿（１０）－Ｌ＿（Ｌｃ１２）．根据Ｒｅｘｅｄ的细胞构筑原则将其灰质分为１０层,并对每层及其相关神经核的关系作了描记。在全髓白质中均发现特殊细胞群,包括侧索中的颈、胸、腰尾外侧核,背索中的脊髓背索核,以及腹索中的散在细胞。还发现其软膜内陷到脊髓深部,在白质和灰质中形成腔隙和管道并充满脑脊液,神经细胞浸于脑脊液中。作者认为这些细胞应是接触脑脊液神经元（ＣＳＦ－ＣＮ）。     

Cauda equina syndrome and nitric oxide synthase immunoreactivity in the spinal cord of the dog

The development of the cauda equina syndrome in the dog and the involvement of spinal nitric oxide synthase immunoreactivity (NOS-IR) and catalytic nitric oxide synthase (cNOS) activity were studied in a pain model caused by multiple cauda equina constrictions. Increased NOS-IR was found two days post-constriction in neurons of the deep dorsal horn and in large, mostly bipolar neurons located in the internal basal nucleus of Cajal seen along the medial border of the dorsal horn. Concomitantly, NOS-IR was detected in small neurons close to the medioventral border of the ventral horn. High NOS-IR appeared in a dense sacral vascular body close to the Lissauer tract in S1-S3 segments. Somatic and fiber-like NOS-IR appeared at five days post-constriction in the Lissauer tract and in the lateral and medial collateral pathways arising from the Lissauer tract. Both pathways were accompanied by a dense punctate NOS immunopositive staining. Simultaneously, the internal basal nucleus of Cajal and neuropil of this nucleus exhibited high NOS-IR. A significant decrease in the number of small NOS immunoreactive somata was noted in laminae I-II of L6-S2 segments at five days post-constriction while, at the same time, the number of NOS immunoreactive neurons located in laminae VIII and IX was significantly increased. Moreover, high immunopositivity in the sacral vascular body persisted along with a highly expressed NOS-IR staining of vessels supplying the dorsal sacral gray commissure and dorsal horn in S1-S3 segments. cNOS activity, based on a radioassay of compartmentalized gray and white matter regions of lower lumbar segments and non-compartmentalized gray and white matter of S1-S3 segments, proved to be highly variable for both post-constriction periods.     

中华白海豚脊髓的解剖学和C6、T8、Lc2的组织学研究

对1头雌成体中华白海豚的脊髓从宏观到微观研究其形态结构。光镜观察标本取自C₆ 、T₈ 和 Lc₂, 冰切20～40μm, 硫堇及镀银两法染色。脊髓式为 C₈-T₁₂-L₁₀-Ca₄ (或 Lc₁₄)。脊髓长占体长的27.48 %, 脊髓重占脑重的3.88%。蛛网膜小梁异常发达呈薄丝绵状, 软脊膜携血管随沟、裂内陷入脊髓实质。灰、白质具不规则血管周隙, 含淋巴细胞及脑脊液。神经细胞与微血管浸于脑脊液中, 故神经细胞为CSF-CN。根据 Rexed 的细胞构筑原则, 可将C₆、T₈、Lc₂灰质分为10层, 并对每层及其相关神经核关系作了描述。在上述3节白质侧索、背索和腹索中均发现特殊细胞群, 即: 颈外侧核、胸外侧核和腰尾外侧核; 背索核和腹索中的弥散性细胞。
     

Growth factor receptors in amyotrophic lateral sclerosis

The regional distribution of nerve growth factor (NGF) and insulin-like growth factor-1 (IGF-1) receptors in human spinal cords from controls and amyotrophic lateral sclerosis (ALS) patients was studied by quantitative autoradiography. High-affinity nerve growth factor receptors were found to be distributed to a similar extent within the various segments of the human spinal cord and predominantly within the substantia gelatinosa of the dorsal horn, whereas no significant binding could be detected in the motor-neuron areas. A similar pattern of binding was obtained in the ALS spinal cords. Moreover, no reexpression of NGF receptors could be demonstrated in the motor-neuron areas of ALS spinal cords. When comparing¹²⁵I-IGF-1 binding in the different spinal levels of normal spinal cord, the same distribution pattern was found in which the binding was highest in the central canal > dorsal horn > ventral horn > white matter. In the ALS cases, although a general upregulation of IGF-1 receptors was observed throughout the spinal cord, significant increases were observed in the cervical and sacral segments compared to controls. The cartography of IGF-1 receptors in the normal spinal cord as well as the change of these receptors in diseased spinal cord may be of importance in future treatment strategies of ALS.     

Catalytic nitric oxide synthase activity in the white and gray matter regions of the spinal cord of rabbits

The latest research reveals that nitric oxide as a gas messenger may diffuse into the surrounding extracellular fluid and act locally upon neighboring target cells. However, several observations raise the possibility that nitric oxide may also be released at a greater distance from the neuronal cell body. The catalytic nitric oxide synthase (cNOS) activity was therefore studied in the cervicothoracic and lumbosacral segments of the spinal cord of rabbits, including the white matter of dorsal columns (DC), lateral columns (LC) and ventral columns (VC), as well as the gray matter of dorsal horns (DH), intermediate zone (IZ) and ventral horns (VH). Lower cNOS activity was found in the white matter of both cervicothoracic (47%) and lumbosacral (30%) regions, whereas that detected in the gray matter of the lumbosacral part of the spinal cord was considerably higher (70%). Enzyme activity varied from 43.4 to 77.2 dpm/microg protein in the cervicothoracic segments of the gray matter in the descending order: DH>VH>IZ. Similar cNOS activity was found in the white matter of the cervicothoracic segments (42.1-62.8 dpm/microg protein). When the activity of cNOS was compared in the lumbosacral segments, the highest enzyme activity was found in DH of the gray matter (198.7 dpm/microg protein) and the lowest cNOS in DC (45.8 dpm/microg protein) of the white matter. It was concluded that the white matter of the spinal cord contains similar cNOS activity in comparison to the gray matter.     

Locomotion induced by epidural stimulation in a decerebrated cat after spinal cord injury

The effect of partial and complete spinal cord transection (Th7–Th8) on locomotor activity evoked in decerebrated cats by electrical epidural stimulation (segment L5, 80–100 μA, 0.5 ms at 5 Hz) has been investigated. Transection of dorsal columns did not substantially influence the locomotion. Disruption of the ventral spinal quadrant resulted in deterioration and instability of the locomotor rhythm. Injury to lateral or medial descending motor systems led to redistribution of the tone in antagonist muscles. Locomotion could be evoked by epidural stimulation within 20 h after complete transection of the spinal cord. The restoration of polysynaptic components in EMG responses correlated with recovery of the stepping function. The data obtained confirm that initiation of locomotion under epidural stimulation is caused by direct action on intraspinal systems responsible for locomotor regulation. With intact or partially injured spinal cord, this effect is under the influence of supraspinal motor systems correcting and stabilizing the evoked locomotor pattern.     

Glucocorticoid Receptors and Enzyme Induction in the Spinal Cord of Rats: Effects of Acute Transection

The spinal cord is a glucocorticoid-responsive tissue, as demonstrated by hormonal effects on enzyme induction and by the presence of type II and type I glucocorticoid receptors in cytoplasmic extracts of this CNS region. Using microdissection techniques, we have found in the present investigation that glucocorticoid type II receptors are the most abundant class detected in gray (ventral and dorsal horns) and white (lateral funiculus) matter and that the distribution of type II sites among these regions was quantitatively similar. Type I sites were also quantified, with a slight prevalence in gray matter as opposed to white matter. Furthermore, stimulation of an inducible enzyme, ornithine decarboxylase (ODC), was found in ventral horn and lateral funiculus but not in dorsal horn after administration of dexamethasone (DEX), a type II receptor ligand. We also found that surgical transection of the spinal cord, while markedly increasing ODC activity per se, did not prevent the stimulatory effect of DEX administration on ODC activity measured in the lumbar enlargement of the spinal cord located below the surgical lesion. Taken together, the results suggest a direct effect of glucocorticoids on ODC activity in the spinal cord of rats, probably mediated by glucocorticoid receptors (type II) found in target cells of the ventral horn and lateral funiculus. The results also indicate that glucocorticoid receptors of the dorsal horn were not involved in ODC induction, and a function for these receptors awaits the results of further experimentation.     

Distribution of Calcitonin Gene-Related Peptide in Rat and Rabbit Spinal Cords: Effect of Intrathecal 5,7-Dihydroxytryptamine

Calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured in selected regions of the cervical, thoracic, and lumbar spinal cord of untreated rabbits and, following intrathecal injection of the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), in the thoracolumbar cord in rats using a sheep antiserum raised against tyrosine0 calcitonin gene-related peptide28-37. In the cervical, thoracic, and lumbar segments of the rabbit spinal cord, CGRP-LI levels were 15-50-fold higher in the dorsal than in the ventral grey region in the same segment. The only segmental variation in CGRP-LI levels was in the dorsal white region, where levels in the thoracic cord were lower than those in cervical or lumbar segments. Within individual spinal segments, the pattern of distribution of CGRP-LI in the rabbit spinal cord was analogous to that in other species previously examined, including rat, human, and cat spinal cord. Intrathecal injection of 5,7-DHT, which caused 85-91% depletion of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid from the thoracolumbar ventral spinal cord, did not affect choline acetyltransferase activity, which is colocalized with CGRP in motoneurones in this spinal cord region. In contrast, intrathecal 5,7-DHT produced a threefold increase in CGRP-LI in the ventral thoracolumbar cord, suggesting that spinal motoneurones selectively increase production of CGRP 10 days after neurotoxin-induced denervation of bulbospinal raphe neuronal input.     

A well defined spinocerebellar system in the weakly electric teleost fish Gnathonemus petersii. A tracing and immuno-histochemical study.

Long ascending fiber systems were investigated in the spinal cord of a teleost fish, Gnathonemus petersii. Concomitant results of Fink-Heimer degeneration tracing as well as CaBP28K immunohistochemical labelling demonstrate the existence of a well defined direct pathway from the very lowest spinal level to the caudal lobe of the cerebellum. HRP retrograde labelling shows that this pathway originates in a cellular column located in the most ventral part of the lateral column next to the lateral extremity of the ventral horn. From each spinal segment, the large axons of these cells gather and form a strip shaped tract at the periphery of the lateral column immediately dorsal to the cell column from which they originate. The spinal course of these fibers is ipsilateral; they give off a large number of collaterals to the lateral reticular nucleus. Bypassing the trigeminal motor nucleus, the lateral column tract courses dorsally to the paratrigeminal command associated nucleus between the lateral lemniscus and the nucleus preeminentialis and with a ventro-dorsally oriented large loop, turns in the caudal direction and penetrates into the cerebellar caudal lobe. Running caudally in the dorsal granular layer of the caudal lobe, it shifts more and more medially and crosses the midline whilst decussating with the contralateral tract on the dorsal margin of the molecular layer of the caudal lobe. Finally, the tract splits off and terminates throughout the granular layer of the caudal lobe. The main characteristics of this pathway are similar to those of the ventral spinocerebellar tract of higher vertebrates; it conveys information from all spinal levels directly to the contralateral cerebellum. However, it does not seem to receive direct synaptic input from the periphery, since projection of the dorsal root fibers appears to be limited to the dorsal ipsilateral half of the spinal cord. The appearance of such a pathway in a teleost fish is probably related to the existence of a well developed proprioceptive system in this species.     

THE DISTRIBUTION OF GLYCINE, GABA, GLUTAMATE AND ASPARTATE IN RABBIT SPINAL CORD, CEREBELLUM AND HIPPOCAMPUS

The distribution of glycine, GABA, glutamate and aspartate was measured among about 60 subdivisions of rabbit spinal cord, and among the discrete layers of cerebellum, hippocampus and area dentata. A more detailed mapping for GABA was made within the tip of the dorsal horn of the spinal cord. Spinal ventral horn and dorsal root ganglion cell bodies were analyzed for the amino acids and for total lipid. The distribution of lipid and lipid-free dry weight per unit volume was also determined in spinal cord. Calculated on the basis of tissue water, glycine in the cord is highest in lateral and ventral white matter immediately adjacent to the ventral grey. The distribution of GABA is almost the inverse of that of glycine with highest level in the tip of dorsal horn. It is most highly concentrated in the central 75% of Rexed layers III and IV. Aspartate in the tip of ventral horn is 4-fold higher than in the tip of the dorsal horn and 3 times the average concentration in brain. Glutamate was much more evenly distributed and is relatively low in concentration with slightly higher levels in dorsal than in ventral grey matter. Large cell bodies in both ventral horn and dorsal root ganglion contained high levels of glycine. As reported by others, GABA was found to be high in cerebellar grey layers, area dentata, and regio inferior of hippocampus. Glycine was moderately high in cerebellar layers but moderate to low in hippocampus and area dentata.     

Regional Distribution of Immunoreactive-Thyrotrophin-Releasing Hormone and Substance P, and Indoleamines in Human Spinal Cord

The regional distributions of thyrotrophin-releasing hormone (TRH) and substance P in postmortem human spinal cord were determined by radioimmunoassay in fresh tissue taken from 22 patients who died without known neurological disease. Dorsal, ventral, and intermediolateral spinal cord regions were obtained from different segmental levels (lumbar L1, 2, 3, and 4; thoracic groups T1-3, T4-6, T7-9, and T10-12) together with selective regions of grey matter of lumbar spinal cord. The effects on peptide levels of the age of the patient, the postmortem time interval, and freezing the tissue samples prior to assay were assessed. Levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were determined in regional lumbar and thoracic tissue using HPLC with electrochemical detection. Substance P was found in the highest concentration in the dorsal spinal cord, with no significant segmental differences. In contrast, TRH was present in higher levels in the ventral rather than the dorsal spinal cord, with segmental differences. There was a significant difference in the 5-HT/5-HIAA ratio between dorsal and ventral spinal cord, with the highest ratio in the ventral spinal cord. There were no significant differences in substance P, TRH, or 5-HT levels in spinal cords between 5 and 20 h postmortem or from patients aged between 65 and 90 years. Freezing the tissue (-80 degrees C for 24 h) prior to assay significantly reduced TRH and substance P levels compared to samples assayed immediately without prior freezing.(ABSTRACT TRUNCATED AT 250 WORDS)     

The regional changes of the catalytic NOS activity in the spinal cord of the rabbit after repeated sublethal ischemia

The regional distribution of catalytic NOS activity was studied in the lumbosacral segments of the spinal cord of the rabbit during single (8-min), twice (8-, 8-min) and thrice repeated (8-, 8-, 9-min) sublethal ischemia followed each time by 1h of reperfusion. Single ischemia/reperfusion induced a significant increase of cNOS activity in almost all spinal cord regions, with the exception of non-significant increase in the dorsal horn. Sublethal ischemia repeated twice produced a significant decrease of enzyme activity in the intermediate zone and ventral horn and an increase in the white matter columns. Within thrice repeated ischemia, the activity of cNOS in the gray matter regions was similar to that found after a single ischemia/reperfusion. For all the animals subjected to single and twice repeated sublethal ischemic insults, there was no neurological impairment. Following thrice repeated ischemic insults, four out of five of the experimental animals recovered only partially and one was completely paraplegic. Our results do not indicate a cumulative effect of repeated sublethal ischemia on cNOS activity and, consequently, on NO production. The NO generated during thrice repeated ischemia/reperfusion appears to have a detrimental effect on the neurological outcome.