Effects of chronic administration of sibutramine on body weight, food intake and motor activity in neonatally monosodium glutamate-treated obese female rats: relationship of antiobesity effect with monoamines.

When the hypothalamic ventromedial nucleus and arcuate nucleus were destroyed in rats by treatment with monosodium glutamate in the neonatal stage, increase in the Lee index (body weight 1/3/body length) and in retroperitoneal fat as well as decreases in spontaneous motor activity, food consumption and growth hormone secretion function associated with hypothalamic low body length obesity (monosodium glutamate-treated obesity; MSG-OB) were observed as these rats grew. Treatment with sibutramine at 3 and 10 mg/kg p.o. once a day continuously for 14 days improved these parameters, and the degree of improvement was dose related. The plasma lipid values in MSG-OB rats, which were the same as those in normal rats, were decreased by consecutive administration of sibutramine. Levels of hypothalamic monoamines (MAs) such as norepinephrine, 5-HT (serotonin) and dopamine and their metabolites DOPAC, HVA and 5-HIAA were decreased in MSG-OB rats, and further decrease in them, though slight, was observed with consecutive daily administration of sibutramine, probably as a result of the feedback attributable to an increase in MA in synapses caused by inhibition of MA uptake by sibutramine. These results suggest that sibutramine can activate the MA nervous system by MA uptake inhibition in regions of the brain such as the lateral hypothalamic area and the paraventricular nucleus, which control food intake and sympathetic nerve activity, and the nigrostriatal area related to the extrapyramidal motor system, and thereby exhibit anti-obesity effects in the MSG-OB rat.     

Striatal dopamine release and biphasic pattern of locomotor and motor activity under gas narcosis

Inert gas narcosis is a neurological syndrome appearing when humans or animals are exposed to hyperbaric inert gases (nitrogen, argon) composed by motor and cognitive impairments. Inert gas narcosis induces a decrease of the dopamine release at the striatum level, structure involved in the regulation of the extrapyramidal motricity. We have investigated, in freely moving rats exposed to different narcotic conditions, the relationship between the locomotor and motor activity and the striatal dopamine release, using respectively a computerized device that enables a quantitative analysis of this behavioural disturbance and voltammetry. The use of 3 MPa of nitrogen, 2 MPa of argon and 0.1 MPa of nitrous oxide, revealed after a transient phase of hyperactivity, a lower level of the locomotor and motor activity, in relation with the decrease of the striatal dopamine release. It is concluded that the striatal dopamine decrease could be related to the decrease of the locomotor and motor hyperactivity, but that other(s) neurotransmitter(s) could be primarily involved in the behavioural motor disturbances induced by narcotics. This biphasic effect could be of major importance for future pharmacological investigations, and motor categorization, on the basic mechanisms of inert gas at pressure.     

Cathepsin B-dependent motor neuron death after nerve injury in the adult mouse

There are significant differences in the rate of neuronal death after peripheral nerve injury between species. The rate of neuronal death of motor neurons after nerve injury in the adult rats is very low, whereas that in adult mice is relatively high. However, the understanding of the mechanism underlying axotomy-induced motor neuron death in adult mice is limited. Cathepsin B (CB), a typical cysteine lysosomal protease, has been implicated in three major morphologically distinct pathways of cell death; apoptosis, necrosis and autophagic cell death. The possible involvement of CB in the neuronal death of hypogrossal nucleus (HGN) neurons after nerve injury in adult mice was thus examined. Quantitative analyses showed the mean survival ratio of HGN neurons in CB-deficient (CB−/−) adult mice after nerve injury was significantly greater than that in the wild-type mice. At the same time, proliferation of microglia in the injured side of the HGN of CB−/− adult mice was markedly reduced compared with that in the wild-type mice. On the injured side of the HGN in the wild-type adult mice, both pro- and mature forms of CB markedly increased in accordance with the increase in the membrane-bound form of LC3 (LC3-II), a marker protein of autophagy. Furthermore, the increase in CB preceded an increase in the expression of Noxa, a major executor for axotomy-induced motor neuron death in the adult mouse. Conversely, expression of neither Noxa or LC3-II was observed in the HGN of adult CB−/− mice after nerve injury. These observations strongly suggest that CB plays a critical role in axotomy-induced mortor neuron death in adult mice.     

Brain phagocytes may empty tissue debris into capillaries

The possibility that brain phagocytes may empty remnants of degenerated neurons into capillaries has been studied in frogs. Degeneration of nerve fibers was brought about by transectioning the optic tract, the tectothalamic and tectoisthmic tracts, the postoptic commissure or the radial nerve. To help identification of phagocytozed degenerated neuronal elements, the transected fibers were filled either with horseradish peroxidase (HRP) or cobaltous-lysine complex. The survival times were 3, 4, 7, 27, 47 and 70 days after the application of the markers. The HRP-labeled structures were identified in 60 μm thick sections using diaminobenzidine as chromogen, while cobalt was precipitated in the form of cobaltous sulfide. Small pieces of these sections were further processed for electron microscopy. In each area of the brain and spinal cord investigated, microglial cells and astrocytic processes containing fragments of degenerated neuronal elements could be seen close to capillaries. In some cases a microglial or astrocytic process pierced the capillary basal lamina and seemingly delivered inclusion bodies into the cytoplasm of capillary endothelial cells and pericytes. In the inclusion bodies, which were usually large vesicles, fragments of HRP or cobalt-labeled or unlabeled membranes with a foamy appearance, or condensed myelin lamellae could be observed. These vesicles protruded the luminal membrane of the endothelial cell that was disrupted in some cases suggesting that the content of the inclusion body was discharged into the lumen of the capillary. These results give support to Penfield's hypothesis (1925) that glial cells may empty phagocytozed materials into capillaries.     

The superior colliculus, a neuronal network resistant to the Gaba withdrawal syndrome

Chronic intracortical perfusion of GABA (Gamma Amino Butyric Acid) and its subsequent withdrawal generates the GABA withdrawal syndrome (GWS). This particular epileptic model has been observed in the motor cortex of monkeys and rats. Our purpose was to study the GWS in the motor cortex (MC), dorsal hippocampus (DH), and superior colliculus (SC). Thirty chronically-implanted adult Wistar rats were separated into 3 groups of 10 (8 experimental and 2 controls). The first group received GABA in MC, the second in the DH and the third in the SC. GABA was released in doses of 10 to 60 micrograms/microliter/h for 6 days employing osmotic mini-pumps. Two control rats per group received saline solution in the above-mentioned structures. Rats perfused in the MC showed GWS after interruption of the GABA flow. The group perfused in the DH showed paroxysmal discharges and epileptic seizures during perfusion. They also later showed GWS. No epileptic effects were observed in the SC-perfused group during either the GABA perfusion or during withdrawal. None of the six control animals showed epileptic effects. Our results show that the SC offers a strong resistance to GWS. This could be explained by the particular neuronal network structure of rat SC.     

Non-junctional modulation of neurogenic twitches of the guinea-pig ileum by some peptides and other compounds in the triple bath

The effects of some neuropeptide transmitter candidates and of some other neurotoxins or drugs on conduction of neural excitation were studied in myenteric plexus-longitudinal muscle strips from the guinea-pig ileum. A preparation in a special triple bath was drawn through two rubber membranes dividing the strip into three segments. Neurogenic stimulation of the oral segment set up nerve action potentials propagating aborally across the middle segment so that the aboral segment might also be invaded. Drugs were added to the middle segment to affect neuronal propagation (non-junctional effects) which was monitored by twitch amplitude of the aboral segment. The application of bradykinin and cromakalim did not affect aboral twitches although strong contractile and relaxatory effects were observed when the drugs were applied directly to the aboral segment; no neurogenic effects thus manifested. Capsaicin and neurotensin, when applied both to the middle and aboral segments, elevated the tone of the preparations accompanied with a decrease in twitch amplitude; these effects may have been due to neurogenic stimulation and release of other motor neurotransmitters. The application of VIP, apamin and dendrotoxin to the middle as well as to the aboral segments augmented aboral twitches, which might be at least partly due to facilitation of nerve action potential propagation in nerve terminals of cholinergic motor fibres.     

Effects of intranasally administered substance P in parkinsonian syndrome]

The effect of intranasal substance P injection on parkinsonian syndrome and the generator of pathologically enhanced excitation (GPEE) in caudate nuclei (CN) was investigated. MPTP or reserpine administration in old rats induced oligokinesia, rigidity and tremor followed by the high amplitude slow and rapid waves in both CN. The bilateral intranasal injection of substance P (25 micrograms/kg) resulted in an increase in motor activity and almost completely abolished the rigidity and tremor. The reduction of extrapyramidal symptoms was considered as a result of the inhibition of GPEE in CN. The possibility of substance P entry from nasal cavity into the brain was discussed. The changes of the substance P balance in nigrostriatal system was suggested to be on of the pathogenetic links of parkinsonian syndrome.     

Reduced Axoplasmic Somatostatin Transport in Hypothyroid Rats

The effect of hypothyroidism on neuronal function was studied by measuring axoplasmic transport of immunoreactive somatostatin in rat sciatic nerve by the ligation technique. Accumulation of immunoreactive somatostatin proximal to a ligature was linear up to 8 h in normal, in thyroidectomized, and in parathyroidectomized rats. The transport rate was decreased by 38% in thyroidectomized rats as compared to normal rats and was unchanged in parathyroidectomized rats. Sciatic nerve content of somatostatin in hypothyroid rats did not differ from control. Reduced accumulation of immunoreactive somatostatin in hypothyroid rats may be due to a decrease in somatostatin synthesis or in axoplasmic transport, or to an increase in the degradation rate of the peptide.     

Morphological changes in locus ceruleus of albino rats in relation to aging

Comparative studies were carried out under light, fluorescence- and electron-microscopic observations between young, adult and aged groups of albino rats with the following results: the neuronal packing density of locus ceruleus decreases with advanced age. In addition to the senescent loss of nerve cells, the surviving ones showed some shrinkage of perikarya and reduction or loss of Nissl substance. Some of them presented pyknosis, chromatolysis and loss of RNA in cytoplasm. Glial cells proliferated around the degenerating cells. Senescent cells showed an increase of heterochromatin and decrease of euchromatin. Changes in cytoplasmic organelles included the decrease of ribosomes, alterations in mitochondria and increase of lipofuscins. These senescent changes were thought to affect the absorption of nutrition, message exchange, protein synthesis, supply of energy and transport of materials by the nerve cells.     

Hemodynamic vertebrobasilar insufficiency demonstrated by chronic oligemic cerebral flow and cerebellar ataxia: two new concepts

We propose in the paper of the concept of nuclear hemodynamic vertebrobasilar insufficiency, defined as an oligemic blood flow lower than 35 ml/100 g/min. in the brain stem-cerebellum zone, when using the method of inhalation of 133Xe. In 15 patients, the neurophysiologic manifestations included intermittent symptoms. We describe here permanent neurophysiologic motor disturbances: extrapyramidal Dopa sensitive syndrome (2/15), chronic cerebellar ataxia (12/15), often associated with cerebellar atrophy (8/12). The concept of chronic oligemic cerebellar ataxia, corresponding to selective neuronal death and/or neurochemical failure, is proposed.     

Attenuation of vascular/neural dysfunction in Zucker rats treated with enalapril or rosuvastatin

Objective: Obese Zucker rats, animal model for the metabolic syndrome, develop a diabetes‐like neuropathy that is independent of hyperglycemia. The purpose of this study was to determine whether drugs used to treat cardiovascular dysfunction in metabolic syndrome also protect nerve function. Methods and Procedures: Obese Zucker rats at 20 weeks of age were treated for 12 weeks with enalapril or rosuvastatin. Lean rats were used as controls. Vasodilation in epineurial arterioles was measured by videomicroscopy. Endoneurial blood flow (EBF) was measured by hydrogen clearance and nerve conduction velocity was measured following electrical stimulation of motor or sensory nerves. Results: Enalapril treatment decreased serum angiotensin‐converting enzyme (ACE) activity and both drugs reduced serum cholesterol levels. In obese Zucker rats at 32 weeks of age superoxide levels were elevated in the aortas and epineurial arterioles, which were reduced by treatment with either drug. Nitrotyrosine levels were increased in epineurial arterioles and reduced with enalapril treatment. EBF was decreased and corrected by treatment with either drug. Motor nerve conduction velocity was decreased and significantly improved with enalapril treatment. Obese Zucker rats were hypoalgesic in response to a thermal stimulus and this was significantly improved with either treatment. Treatment with either enalapril or rosuvastatin significantly reversed the decrease in acetylcholine‐mediated vascular relaxation of epineurial arterioles in obese Zucker rats. Discussion: Even though obese Zucker rats have normal glycemia vascular and neural dysfunctions develop with age and can be improved by treatment with either enalapril or rosuvastatin.     

Analysis of gene expression profile of peripheral ganglia in early stage type Ⅱ diabetic rats

Diabetic neuropathy (DN) is defined as the presence of symptoms and/or signs of peripheral nerve dysfunction in people with diabetes. The aim of this study is to screen differentially expressed genes in peripheral ganglia in early stage type Ⅱ experimental diabetic rats. We compared gene expression profiles of peripheral ganglia in type Ⅱ diabetic and nondiabetic rats based on Illumina? Sentrix? BeadChip arrays. The results showed that 158 out of a total of 12 604 known genes were significantly differentially expressed, including 87 up-regulated and 71 down-regulated genes, in diabetic rats compared with those in the nondiabetic rats. It is noted that some up-regulated genes are involved in the biological processes of neuronal cytoskeleton and motor proteins. In contrast, the down-regulated genes are associated with the response to virus\biotic stimulus\ other organism in diabetic rats. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the most significant pathway enriched in the changed gene set is metabolism (P < 0.001). These results indicated that metabolic changes in peripheral ganglia of diabetic rats could be induced by hyperglycemia. Hyperglycemia could change the expression of genes involved in neuronal cytoskeleton and motor proteins through immune inflammatory response, and then impair the structure and function of the peripheral ganglia.     

2型糖尿病早期大鼠外周神经节基因表达谱分析

糖尿病神经病变(Diabetic neuropathy,DN)是糖尿病在神经系统发生的多种并发病变的总称。文章旨在筛选2型糖尿病早期大鼠外周神经节差异表达的基因。采用Illumina大鼠基因表达芯片,比较糖尿病模型与非糖尿病大鼠外周神经节基因表达谱差异。结果表明,全基因组12 604个已知基因中,158个基因差异表达。糖尿病组与非糖尿病组相比,87个基因表达上调,71个表达下调。对差异表达的基因进行GO分析,发现上调基因所参与的最显著(P<0.001)的几个生物学过程都与神经细胞骨架及运动功能有关;下调基因所参与的最显著的生物学过程主要与"对病毒/生物刺激/其它生物的反应"有关。KEGG(Kyoto encyclopedia of genes and genomes)分析显示,差异表达的基因所参与的最显著(P<0.001)的生物学通路为代谢通路。结果表明:高血糖可导致糖尿病大鼠外周神经节代谢紊乱;高血糖可能通过免疫炎症反应、改变神经细胞骨架及运动功能相关的基因的表达,继而损害外周神经节的结构和功能。     

Fluorescence Changes in Nerve Induced by Stimulation : Their relation to protein configuration

It was previously assumed, on the basis of changes in the ultraviolet absorption spectrum and of increase in ionizable sulfhydryl groups, that during excitation the proteins of excitable structures undergo some structural rearrangements, and these rearrangements may be similar to those designated by the term transconformation. In the present experiments, it was observed that electrical stimulation of peripheral nerves from rat, guinea pig, frog, and crab causes a decrease in their fluorescence. The peaks of the emission and activation spectra correspond to those attributed to proteins. Denaturing agents, such as urea, were also found to decrease the fluorescence of nerve extracts. It is, therefore, probable that the decrease in fluorescence, associated with the excited state, is due to a change in the configuration of the nerve proteins. The fluorescent method is applicable not only to tissue extracts but allows the observation of surviving nerve fibers before, during, and after stimulation. It showed that fluorescence of the fibers decreases invariably during stimulation and tends to return to the control level during restoration. The reduction in fluorescence is quantitatively related to the number of stimuli received by the nerve.     

Functional deficits in skeletal muscle grafts

Individual skeletal muscle fibers degenerate and regenerate with minimal functional deficits. When whole skeletal muscles are grafted in rats or cats by standard grafting techniques, revascularization and reinnervation must occur spontaneously. Under these circumstances, contraction times and maximum velocities of shortening eventually return to control values, but a significant deficit is observed in maximum tetanic tension. Grafts made with anastomosis of nerves or with nerves left intact have smaller deficits in tension development than do standard grafts made without nerve repair. The measurement of contractile properties of single motor units in extensor digitorum longus (EDL) muscles and in EDL grafts in rats indicates that the decreased maximum tetanic tension of whole grafts is due to a 10-20% decrease in the maximum tetanic tension of individual motor units, whereas standard grafts also show a 40-45% decrease in the number of motor units. Compared with control values, the fatigability of 100-mg grafts in rats is decreased, whereas larger 3-g grafts in cats show an increased fatigability. The deficits observed in large grafts can be reduced, but not eliminated, by grafting with neurovascular anastomoses.     

Manganese neurotoxicity: a model for free radical mediated neurodegeneration?

In man, manganese neurointoxication is characterised in the early phase by behavior reminiscent of that observed in schizophrenia. During chronic manganese intoxication the neuropsychiatric symptoms manifested earlier disappear and are followed by a permanent neurological phase typified by extrapyramidal symptoms similar to those of Parkinson's disease. Study of manganese intoxication in animals may provide important clues towards elucidation of the biochemical defect underlying neuropsychiatric as well as extrapyramidal disease. Investigations in our laboratory suggest that neurotoxicity of manganese is an exaggeration of function in normal neuronal homeostasis. Manganese neurointoxication in neonatal rats resulted in significant depression of lipid peroxidation in several rat brain regions examined. In the striatum, lipid peroxidative activity was abolished, an effect which may be related to alteration in neurotransmitters often observed in the striatum of manganese treated rats. The chronic, extrapyramidal stage of manganism, may ensue when excess Mn2+ is oxidised to higher valency forms where it can potentiate the autoxidation of catecholamines, like dopamine, resulting in concomitant formation of free radicals and cytotoxic quinones. This latter effect may arise preferentially in the substantia nigra, where neuromelanin is formed nonenzymatically by autoxidation of dopamine.     

Effect of Treadmill Exercise on Serotonin Immunoreactivity in Medullary Raphe Nuclei and Spinal Cord Following Sciatic Nerve Transection in Rats

The serotoninergic system modulates nociceptive and locomotor spinal cord circuits. Exercise improves motor function and changes dopaminergic, noradrenergic, and serotonergic central systems. However, the direct relationship between serotonin, peripheral nerve lesion and aerobic treadmill exercise has not been studied. Using immunohistochemistry and optic densitometry, this study showed that the sciatic nerve transection increased the serotoninergic immunoreactivity in neuronal cytoplasm of the magnus raphe nuclei of trained and sedentary rats. In the dorsal raphe nucleus the increase only occurred in sedentary-sham-operated rats. In the spinal cord of trained, transected rats, the ventral horn showed significant changes, while the change in dorsal horn was insignificant. Von Frey’s test indicated analgesia in all exercise-trained rats. The sciatic nerve functional index indicated recovery in the trained group. Thus, both the aerobic treadmill exercise training and the nervous lesion appear to contribute to changes in serotonin immunoreactivity.     

Quantitative freeze-fracture analysis of the frog neuromuscular junction synapse – II. Proximal–distal measurements

Neurotransmitter release from different parts of frog motor nerve terminals is often non-uniform. There is a decrease in release efficacy from the distal regions of frog motor nerve terminal branches. Since release is thought to occur near the double arrays of large intramembranous particles that constitute the pre-synaptic active zones (AZs), we have examined quantitatively the proximal–distal distribution of AZ structure, using a novel freeze-fracture technique that produces replicas of large fractions of terminals, including the region of nerve entry. This enables us to know the proximal–distal orientation of each branch. From 23 end-plates we have obtained fractures of 72 branches. For 27 of these branches we have obtained continuous fractures both greater than 25 μm in length and with sufficient information to determine their proximal–distal polarity. Only a few of these branches showed a marked distal decrease in AZ length/unit length of terminal, while several junctions had short regions (5–10 μm), either proximally or distally, that exhibited amounts of AZ that were substantially greater or smaller than the mean value for that terminal branch. The terminal area, post-synaptic gutter width and nerve terminal width all exhibit some distal decline concomitant with the distal tapering of nerve terminal branches. AZ length tends to have the least decline compared to the other parameters. Thus, the vast majority of frog motor nerve terminal branches do not display a significant proximal-distal gradient in the amount of AZ structure/μm terminal length. The present data do not provide an obvious ultrastructural correlate for the distal decline in transmitter release that some authors have observed.     

Effects of prolonged ethanol exposure on the glial fibrillary acidic protein-containing intermediate filaments of astrocytes in primary culture: a quantitative immunofluorescence and immunogold electron microscopic study

We investigated the effects of ethanol exposure on the shape of the cell and the morphology of intermediate filaments (IF) of cortical astrocytes in primary culture. The content and distribution of glial fibrillary acidic protein (GFAP), the major component of glial IF, was assessed using an anti-GFAP monoclonal antibody and fluorescence scanning densitometry together with quantitative pre- and post-embedding immunogold electron microscopy. The astrocytes were from 21-day-old fetuses obtained from both control and chronic alcoholic rats and were cultured for 28 days in the absence or presence of ethanol (25 mM). The main findings were: (a) ethanol-exposed astrocytes failed to develop processes or to acquire a filamentous IF distribution pattern; (b) these cells showed less GFAP than astrocytes without alcohol; (c) ethanol interfered with the reorganization of the anti-GFAP binding sites from clustered to random; and (d) astrocytes from alcohol-exposed fetuses cultured in the absence of ethanol also showed these alterations, suggesting initial damage to astrocyte precursor cells. Since the glial filaments play a crucial role in creating a scaffolding that guides neuronal migration, the effect of ethanol on astrocyte IF may possibly be correlated with the mechanisms underlying mental retardation and motor dysfunction which are characteristics of fetal alcohol syndrome.