Measurement of ataxia and related neurological signs in the laboratory rat

Exercise reduces physical alterations in a rat model of fetal alcohol spectrum disorders

BACKGROUND

Prenatal alcohol exposure (PAE) has serious physical consequences for children such as behavioral disabilities, growth disorders, neuromuscular problems, impaired motor coordination, and decreased muscle tone. However, it is not known whether loss of muscle strength occurs, and which interventions will effectively mitigate physical PAE impairments. We aimed to investigate whether physical alteration persists during adolescence and whether exercise is an effective intervention.

RESULTS

Using paradigms to evaluate different physical qualities, we described that early adolescent PAE animals have significant alterations in agility and strength, without alterations in balance and coordination compared to CTRL animals. We evaluated the effectiveness of 3 different exercise protocols for 4 weeks: Enrichment environment (EE), Endurance exercise (EEX), and Resistance exercise (REX). The enriched environment significantly improved the strength in the PAE group but not in the CTRL group whose strength parameters were maintained even during exercise. Resistance exercise showed the greatest benefits in gaining strength, and endurance exercise did not.

CONCLUSION

PAE induced a significant decrease in strength compared to CTRL in PND21. Resistance exercise is the most effective to reverse the effects of PAE on muscular strength. Our data suggests that individualized, scheduled, and supervised training of resistance is more beneficial than endurance or enriched environment exercise for adolescents FASD.

Biomechanical microenvironmental stimulating effect of pulsed electromagnetic field on the regeneration of crush injured rat sciatic nerve

This study evaluated the biomechanical microenvironmental stimulating effect of pulsed electromagnetic field (PEMF) on the regeneration of crush-injured rat sciatic nerve, when combined with bone marrow mesenchymal stem cells (BMSCs) and recombinant human nerve growth factor (rhNGF-β), in the form of an adenoviral vector-mediated NGF. Sprague-Dawley rats were equally distributed into six groups; PBS, BMSC, NGF-Ad + BMSC, PEMF + PBS, PEMF + BMSC and PEMF + NGF-Ad + BMSC. The PBS group received PBS (volume: 10μL/rat), the BMSC group with BMSCs (1 × 106 cell/10 μL/rat) and NGF-Ad group with the rhNGF-β Ad infected BMSCs (1 × 106 cell/10 μL/rat) immediate after right sciatic nerve crush injury. The PEMF groups were exposed to PEMF of 1mT, 50 Hz, 1 h/day. The rats were observed for 3 weeks. PEMF alone did not showed the positive effect compared with negative control group. The groups transplanted with BMSCs showed higher axonal regeneration compared with the groups without transplantation of the cells whether BMSC was infected with NGF-Ad or not and whether the animals received PEMF. PEMF + NGF-Ad + BMSC group showed the significantly highest number of axons than the other groups. Functionally, all groups showed marked improvement at 3 weeks postoperatively although the difference was not statistically significant among the groups. PEMF showed the positive effect when combined with BMSC and NGF-ad in aspect of number of axons. Therefore, combining the microenvironment stimulation methods of PEMF and conventional methods such as transplantation of stem cells and growth factor could be considered for the regeneration methods in the nerve damage.

Thiamine Deficiency Increases Intrinsic Excitability of Mouse Cerebellar Purkinje Cells

Thiamine deficiency is associated with cerebellar dysfunction; however, the consequences of thiamine deficiency on the electrophysiological properties of cerebellar Purkinje cells are poorly understood. Here, we evaluated these parameters in brain slices containing cerebellar vermis. Adult mice were maintained for 12-13 days on a thiamine-free diet coupled with daily injections of pyrithiamine, an inhibitor of thiamine phosphorylation. Morphological analysis revealed a 20% reduction in Purkinje cell and nuclear volume in thiamine-deficient animals compared to feeding-matched controls, with no reduction in cell count. Under whole-cell current clamp, thiamine-deficient Purkinje cells required significantly less current injection to fire an action potential. This reduction in rheobase was not due to a change in voltage threshold. Rather, thiamine-deficient neurons presented significantly higher input resistance specifically in the voltage range just below threshold, which increases their sensitivity to current at these critical membrane potentials. In addition, thiamine deficiency caused a significant decrease in the amplitude of the action potential afterhyperpolarization, broadened the action potential, and decreased the current threshold for depolarization block. When thiamine-deficient animals were allowed to recover for 1 week on a normal diet, rheobase, threshold, action potential half-width, and depolarization block threshold were no longer different from controls. We conclude that thiamine deficiency causes significant but reversible changes to the electrophysiology properties of Purkinje cells prior to pathological morphological alterations or cell loss. Thus, the data obtained in the present study indicate that increased excitability of Purkinje cells may represent a leading indicator of cerebellar dysfunction caused by lack of thiamine.

Foxa1 and foxa2 are required for the maintenance of dopaminergic properties in ventral midbrain neurons at late embryonic stages

The maintained expression of transcription factors throughout the development of mesodiencephalic dopaminergic (mDA) neurons suggests multiple roles at various stages in development. Two members of the forkhead/winged helix transcription factor family, Foxa1 and Foxa2, have been recently shown to have an important influence in the early development of mDA neurons. Here we present data demonstrating that these genes are also involved in the later maintenance of the mDA system. We conditionally removed both genes in postmitotic mDA neurons using the dopamine transporter-cre mouse. Deletion of both Foxa1 and Foxa2 resulted in a significant reduction in the number of tyrosine hydroxylase (TH)-positive mDA neurons. The decrease was predominantly observed in the substantia nigra region of the mDA system, which led to a loss of TH+ fibers innervating the striatum. Further analysis demonstrated that the reduction in the number of TH+ cells in the mutant mice was not due to apoptosis or cell-fate change. Using reporter mouse lines, we found that the mDA neurons were still present in the ventral midbrain, but that they had lost much of their dopaminergic phenotype. The majority of these neurons remained in the ventral mesencephalon until at least 18 months of age. Chromatin immunoprecipitation suggested that the loss of the mDA phenotype is due to a reduction in the binding of the nuclear orphan receptor, Nurr-1 to the promoter region of TH. These results extend previous findings and demonstrate a later role for Foxa genes in regulating the maintenance of dopaminergic phenotype in mDA neurons.

Atorvastatin preconditioning attenuates the production of endothelin-1 and prevents experimental vasospasm in rats

OBJECTIVE

Induced endothelin-1 (ET-1) production and decreased nitric oxide synthase (NOS) bioavailability have been found in aneurysmal subarachnoid hemorrhage (SAH). Atorvastatin is recognized to have pleiotropic effects including increasing NOS bioavailability as well as reducing inflammation and oxidative damage other than reducing dyslipidemia. This study is of interest to examine the effect of atorvastatin on ET-1/endothelial nitric oxide synthase (eNOS) in experimental SAH.

METHODS

A rodent double-hemorrhage SAH model was employed. Animals were randomly assigned as sham-operated, SAH, vehicle plus SAH, 5 mg/day atorvastatin treatment plus SAH and 5 mg/day atorvastatin precondition plus SAH groups. Administration with atorvastatin (5 mg/day) was initiated 1 week before (precondition) and 24 hr later (treatment). Cerebrospinal fluid samples were collected at 72 hr after second SAH. ET-1 (ELISA) was measured. The basilar arteries (BAs) were harvested and sliced, and their cross-sectional areas were measured. Radiolabeled NOS assay kit was used to detect eNOS.

RESULTS

Morphologically, convoluted internal elastic lamina, distorted endothelial cells and myonecrosis of the smooth muscle were predominantly observed in the BA of SAH and vehicle-treated SAH groups, which was not detected in the atorvastatin-preconditioned SAH group or the healthy controls. Significant vasospasm was noted in the vehicle group (lumen potency 64.5%, compared with the sham group, p </= 0.01) and less prominent in the atorvastatin treatment group (lumen potency, 76.6%, p < 0.05). In addition, increased ET-1 levels were found in all the animals subject to SAH (SAH only, SAH plus vehicle and SAH plus atorvastatin reversal) except in the atorvastatin precognition group when compared with the healthy controls (no SAH). Likewise, the levels of expressed NOS in BAs is induced in the atorvastatin groups (both atorvastatin treatment and precondition) when compared with that in the SAH group (p < 0.01).

CONCLUSION

This study offers first evidence that atorvastatin in the preconditioning status reduces the level of ET-1, which corresponds to its antivasospastic effect in the condition of chronic vasospasm. Although there is increased expression of NOS in both atorvastatin precondition and reversal groups, BA's lumen potency is significantly increased in the atorvastatin precondition group when compared with the SAH group (p < 0.01).

Automatic analysis of altered gait in arylsulphatase A-deficient mice in the open field

In current research with laboratory animals, observing their dynamic behavior or locomotion is a labor-intensive task. Automatic continuous monitoring can provide quantitative data on each animal's condition and coordination ability. The objective of the present work is to develop an automated mouse observation system integrated with a conventional open-field test for motor function evaluation. Data were acquired from 86 mice having a targeted disruption of the arylsulphatase A (ASA) gene and having lowered coordinated locomotion abilities as a symptom. The mice used were 36 heterozygotes (12 females) and 50 knockout mice (30 females) at the age of 6 months. The mice were placed one at a time into the test setup, which consisted of a Plexiglas cage (53x34.5x26 cm) and two fluorescent bulbs for proper illumination. The transparent cage allowed images to be captured from underneath the cage, so image information could be obtained about the dynamic variation of the positions of the limbs of the mice for gait reconstruction. Every mouse was recorded for 10 min. Background subtraction and color filtering were used to measure and calculate image features, which are variables that contain crucial information, such as the mouse's position, orientation, body outline, and possible locations for the mouse's paws. A set of heuristic rules was used to prune implausible paw features and label the remaining ones as front/hind and left/right. After we had pruned the implausible paw features, the paw features that were consistent over subsequent images were matched to footprints. Finally, from the measured footprint sequence, eight parameters were calculated in order to quantify the gait of the mouse. This automatic observation technique can be integrated with a regular open-field test, where the trajectory and motor function of a free-moving mouse are measured simultaneously.

Pyridoxine (vitamin B6) neurotoxicity: enhancement by protein-de?cient diet

Large doses of pyridoxine cause injury to the primary sensory neurons in trigeminal and dorsal root ganglia of animals and patients subjected to megavitamin therapy. The increased hazard to subjects with reduced renal excretory function has been explored previously. In the present work, the neurotoxicity of pyridoxine for rats was found to be increased by dietary protein deficiency. A mere 3 or 7 days of pretreatment with either of two protein-deficient diets were sufficient to accelerate and intensify the clinical neurological signs and histological lesions from pyridoxine injections. These results are caused, at least in part, by loss of body weight, decreased protein binding in serum and decreased consumption of water and decreased volume of urine, which reduce the urinary losses of the toxicant. The vitamers related to pyridoxine (pyridoxal, pyridoxamine) and the coenzyme (pyridoxal 5-phosphate) did not cause clinical signs or lesions similar to those produced by pyridoxine even when injected in maximum tolerated doses. Neither a protein-deficient diet nor bilateral nephrectomy changed the results with the vitamers.

Functional evaluation of peripheral nerve regeneration in the rat: walking track analysis

The experimental model of choice for many peripheral nerve investigators is the rat. Walking track analysis is a useful tool in the evaluation of functional peripheral nerve recovery in the rat. This quantitative method of analyzing hind limbs performance by examining footprints, known as the sciatic function index (SFI), has been widely used to quantify functional recovery from sciatic nerve injury in a number of different injury models, although some limitations of the SFI has been questioned by several authors. This article is designed to offer the peripheral nerve investigator a noninvasive method to evaluate quantitatively the integrated motor recovery in experimental studies.

GABAergic modulation of descending inhibitory systems from the rostral ventromedial medulla (RVM). Dose-response analysis of nociception and neurological deficits

We have examined the effects of muscimol and bicuculline microinjected in the rostral ventromedial medulla (RVM) on motor function and on nociception in three pain tests. In Exp. 1 microinjection of muscimol (6.25-400 ng in 1 microl) in the RVM dose-dependently decreased pain threshold of rats and the ED(50) for muscimol was the same in both the hot plate and tail immersion pain tests. In the hot plate test, but not in the tail immersion test, paw withdrawal latencies increased again with high doses of muscimol (75-400 ng). High doses also produced catalepsy. Exp. 2 examined the effects of muscimol (50 ng) and bicuculline (50 ng) over a range of formalin concentrations (0.25-4%) in the formalin test. Muscimol increased responsiveness to formalin and reduced the slope of the formalin dose-response relation. Bicuculline decreased responses to formalin and reduced the slope of the formalin dose-response relation. It is suggested that RVM cells with inhibitory projections to the dorsal horn are not subject to strong GABAergic influence under mild noxious stimulation. RVM cells are thus active, and spinal dorsal horn relay neurons are inhibited. On the other hand, intense noxious peripheral stimulation may stimulate the release of GABA onto RVM cells, which in turn shuts off descending inhibitory fibers to allow transmission of nociceptor input through the dorsal horn.

Glucose loading precipitates acute encephalopathy in thiamin-deficient rats

A rat model of glucose-precipitated Wernicke's encephalopathy (WE) has been developed in which glucose loading (10 g/kg, i.p.) of ataxic thiamin-deficient (TD) rats induced episodes of gross neurological dysfunction and sometimes death. The acute effects of a glucose load on the neurological state of thiamin-replete control and TD rats were assessed by scoring of clinical observations and performance measured on a moving belt (MB) apparatus at 30 min intervals for 2 hr after the challenge. Glucose loading or saline treatment (2.5 mL, i.p.) had no significant behavioural or clinical consequences when administered to controls or rats fed TD diet for <21 days. Glucose loading of ataxic rats fed TD diet for 28-35 days precipitated episodes of gross ataxia and signs of advanced neurological dysfunction (e.g. loss of righting reflex and hyperexcitability) leading to significant increases in the Ataxia (p<0.05) and Advanced Sign (p<0.05) scores within 2 hr after the challenge. Simultaneously, the performance of these animals on the MB decreased 10-fold. Regular glucose challenges significantly increased the rate of progression of disease in TD rats when compared with untreated TD rats. This model may be useful for the further investigation of the pathogenesis of WE at the molecular level.

A low-cost method to analyse footprint patterns

Neurological dysfunction can be assessed by analysing footprint patterns and walking tracks. However, because such an analysis is very time consuming, we developed an MS-Windows program called FOOTPRINTS which facilitates the analysis of the commonly used measures and which is considerably quicker than manual scoring methods. The prints are scanned at a resolution of 75 dpi and stored as black and white bitmaps for further analysis. In order to validate the program, we analysed the footprint patterns of mice and rats, using both the program and the conventional manual scoring method. In the first study, the walking patterns of 3-, 14-, and 26-month-old Janvier Wistar rats were compared, and in the second the footprint patterns of C57BL mice were assessed. Comparison of the data obtained using the program and of the data obtained by manual scoring showed that the computer-based analysis gives reliable results. The program saves considerable time as the analysis took 1/8th of the time needed for manual evaluation.

In vivo central actions of rat amylin

The purpose of the present study was to examine and compare the profile of neurobehavioral effects of rat amylin (r-amylin) and rat calcitonin gene-related peptide (rCGRP), two peptides having a 50% structural homology. The effects of synthetic r-amylin and rCGRP administered in several doses (0.312-80.0 micrograms) into the lateral cerebro-ventricle of rats on spontaneous activity, muscular tone, body temperature, nociception, food intake as well as their potential for inducing catalepsy, were investigated. Intraventricular administration of r-amylin or rCGRP significantly reduced spontaneous motor activity and markedly increased body temperature of animals in a dose-dependent related fashion. rCGRP produced a significant increase in muscular tone and induced cataleptic effect in animals, but r-amylin had no effect on these variables. Furthermore, neither r-amylin nor rCGRP were able to induce any significant effect on nociceptive response time of animals in the tail immersion test even with doses as large as 80.0 micrograms. Finally, the two peptides did not affect ad libitum food intake, but significantly reduced food consumption in 22 h food-deprived animals. Together, the results of the present study suggest that amylin may be involved in a diversity of neurophysiological processes but displays a different profile of neurobehavioral effects to that of CGRP which may involve different receptors.

Structure-activity analysis of the motor effects of neuropeptide Y

The purpose of the present study was to examine structure-activity relationships for three known motor effects of neuropeptide Y (NPY): decreased spontaneous activity, enhancement of muscle tone, and catalepsy. Various NPY fragments and structural analogues were synthesized and administered intracerebroventricularly in several doses (2.5-160 micrograms); their effects on these three motor variables were evaluated and compared. Globally, results indicate that the C-terminal portion of the peptide is responsible for the three motor effects of NPY. However, the distributions of potencies of the various fragments and analogues for each effect were clearly different, suggesting that the putative receptors mediating each motor effect are pharmacologically different. The findings of the present work are discussed in relation to those obtained in previous structure-activity studies.

Regional alterations of thiamine phosphate esters and of thiamine diphosphate-dependent enzymes in relation to function in experimental Wernicke's encephalopathy

Thiamine phosphate esters (thiamine monophosphate-TMP; thiamine diphosphate-TDP and thiamine triphosphate-TTP) were measured as their thiochrome derivatives by High Performance Liquid Chromatography in the brains of pyrithiamine-treated rats at various stages during the development of thiamine deficiency encephalopathy. Severe encephalopathy was accompanied by significant reductions of all three thiamine phosphate esters in brain. Neurological symptoms of thiamine deficiency appeared when brain levels of TMP and TDP fell below 15% of normal values. Activities of the TDP-dependent enzyme alpha-ketoglutarate dehydrogenase were more severely reduced in thalamus compared to cerebral cortex, a less vulnerable brain structure. On the other hand, reductions of TTP, the non-cofactor form of thiamine, occurred to a greater extent in cerebral cortex than thalamus. Early reductions of TDP-dependent enzymes and the ensuing metabolic pertubations such as lactic acidosis impaired brain energy metabolism, and NMDA-receptor mediated excitotoxicity offer rational explanations for the selective vulnerability of brain structures such as thalamus to the deleterious effects of thiamine deficiency.

In vivo central actions of NPY(1-30), an N-terminal fragment of neuropeptide Y

The purpose of the present study was to examine the possible central actions of a N-terminal fragment of NPY, NPY(1-30), on five measures typically influenced by the native peptide: decreased spontaneous activity, enhancement of muscle tone (increased grasping response), catalepsy, hypothermia, and stimulation of food intake. The peptides were administered ICV in doses ranging from 2.5 to 160 micrograms (0.75-48 nmol) and their effects on the three motor variables as well as thermal and feeding responses were evaluated and compared. Globally, results indicate that, similarly to NPY, the N-terminal fragment NPY(1-30), decreased spontaneous activity and induced hypothermia. However, the fragment displayed approximately half of the potency of NPY for producing these effects. On the other hand, contrary to NPY, NPY(1-30) did not affect muscle tone or food consumption and did not induced catalepsy in animals. These results demonstrate for the first time central actions of a N-terminal fragment of NPY and lend further support to the hypothesis that the receptors mediating the central actions of NPY are pharmacologically different.

Pyrithiamine-induced thiamine deficiency results in decreased Ca(2+)-dependent release of glutamate from rat hippocampal slices

Alterations of excitatory amino acids in brain may be of pathophysiological significance in thiamine-deficiency encephalopathy. The present study was undertaken to evaluate the effects of thiamine deficiency induced by the central thiamine antagonist, pyrithiamine, on the glutamate content of glutamatergic nerve terminals. Electrically-stimulated, Ca(2+)-dependent release of glutamate from hippocampal slices obtained from symptomatic pyrithiamine-treated rats was significantly decreased compared to pair-fed controls. Possible explanations for the decreased "neurotransmitter pool" of glutamate in thiamine-deficient rat brain include decreased synthesis of glutamate as a result of decreased activities of the thiamine-dependent enzyme alpha-ketoglutarate dehydrogenase or increased release of glutamate per se. There is evidence to suggest that the latter mechanism with ensuing excitotoxic neuronal damage could be involved in the pathogenesis of selective neuronal death in thiamine deficiency. Similar mechanisms could be implicated in Wernicke's encephalopathy in humans.

Improved imaging of rat hindfoot prints for walking track analysis

Walking track analysis is an investigative technique that allows a researcher to assess objectively the functional capacity of the limb in the rat sciatic nerve model. This study has shown that paint and paper is a better method for imaging the rat foot plantar surface than other methods described in the literature. The block printing paint has the distinct advantage of keeping radial diffusion error to a minimum. Paint more correctly images the important anatomical landmarks of the rat plantar surface. There is better traction (less slippage) rendering the prints easier to interpret. The authors conclude that the paint and paper is a superior method to the other methods currently available.

A toluene-induced motor syndrome in rats resembling that seen in some human solvent abusers

The purpose of these experiments was to determine the extent to which subchronic exposure of rats to toluene might cause symptoms similar to those seen in some heavy abusers of toluene-containing products. In the first exploratory experiment, weanling male Fischer-344 rats were exposed to air, toluene, n-hexane, or a mixture of toluene, n-hexane, and methyl ethyl ketone (8 h per day, 7 days per week) for 11 weeks. A mild peripheral neuropathy was revealed by measures of grip strength in the rats exposed to n-hexane alone or in the mixture, but not in the rats exposed to toluene. Instead, the rats exposed to toluene alone developed a persisting motor syndrome characterized by a shortened and widened gait and a widened landing foot splay. The rats exposed to toluene alone or in the mixture were also hearing impaired, but not the rats exposed to n-hexane alone. In the second experiment, done to confirm and extend these results, weanling male Fischer-344 rats were exposed to toluene under three different daily schedules--2,200 ppm continuously for 8 h per day; 4,400 ppm, 30 min each h, 8 h per day; or 6,200 ppm, 15 min each h, 8 h per day. The exposures were 7 days per week for 23 weeks. The motor syndrome and hearing impairment were replicated in all essential respects in all toluene-exposed groups with no appreciable differences attributable to the daily exposure schedules. The effects were still evident 15 weeks after the last exposure. Toluene inhibited weight gain in both experiments, and in the second experiment, it was found that skeletal growth (torso length, rump width) was also inhibited. Toluene did not significantly impair rotorod performance in either experiment or acquisition of a spatial-navigation task in the second experiment. No neuropathologic correlates of the persisting motor syndrome were found in either experiment when the rats were sacrificed 9 and 16 weeks after the last exposure, respectively. These results demonstrate that toluene can cause a persisting motor syndrome in rats that resembles, to some extent at least (i.e., wide-based ataxic gait), the syndrome seen in some heavy abusers of toluene-containing products.

Neurobehavioral profile of neuropeptide Y

In order to better delineate the profile of central actions of neuropeptide Y (NPY), the effects of intracerebroventricular administration of several doses (2.5-20 micrograms) of the peptide on spontaneous activity, muscular tone, body temperature, food intake, nociception and cataleptic manifestations were examined in rats. Results indicate that, starting at 5 micrograms. NPY significantly decreased motor activity of animals in a dose-related fashion. NPY also significantly lowered body temperature of animals. The hypothermic effect was obtained following injections of 10.0 and 20.0 micrograms of the peptide. Administration of the same two doses of NPY resulted in significant increases in food intake, muscular tone and induced a significant catalepsy in animals. On the other hand, nociceptive response times of animals in the hot plate test were not affected by any of the NPY doses tested. Together, these results indicate that the profile of NPY's neurobehavioral actions is more complex than previously reported and suggest that the peptide might be implicated functionally in a variety of neurophysiological processes.

Neurobehavioral evidence for kappa agonist activity of the morphinan derivative 14-beta-methyl 8-oxacyclorphan [BC (3016)]

The purpose of the present study was to determine if the in vivo neurobehavioral effects of the morphinan 14-beta-methyl 8-oxacyclorphan, [BC (3016)], would reflect the kappa agonist activity found in our previous in vitro studies. The effects of intracisternal administration of various doses (10-80 micrograms) of BC (3016) on body temperature, muscle rigidity, nociception of thermal, chemical and mechanical stimuli as well as its ability to induce catalepsy were examined. The effects of intrathecal administration of the same doses of the compound on reactivity of animals to a thermal stimulus were also assessed. Finally, the ability of BC (3016) to antagonize well known neurobehavioral effects of morphine was investigated. Results indicate that the analgesic properties of BC (3016) resemble those of typical kappa agonists: Intracisternal administration of the drug failed to affect nociception to an aversive thermal stimulus but markedly reduced the reactivity of animals subjected to noxious chemical or mechanical stimuli. On the other hand, intrathecal administration of BC (3016) significantly attenuated nociception of animals to a thermal stimulus. The in vivo neurobehavioral effects of BC (3016) appear to be kappa selective since the drug did not decrease body temperature, increase muscular tone or induce catalepsy, three effects generally attributed to mu agonists. Furthermore, BC (3016) antagonized the immobility, trunk rigidity, catalepsy and analgesia induced by morphine. In summary, the present results reveal that BC (3016) displays a profile of neurobehavioral effects similar to that of well known kappa agonists.

Gait topography in rat locomotion

Gait topography has been quantified and normative data established for free, spontaneous locomotion in rats. The normal walking pattern has been compared for male and female rats and for three rat strains. The normal walking gait was found to be symmetrical, and measures of stride width (SW) and stride length (SL) were consistent, with coefficients of variability ranging between 10 and 21%. A study of gait ontogeny found that for both male and female rats, SL increased as a linear function of body weight, whereas SW increased curvilinearly. The results indicate that repeated measures of gait topography were not subject to interference from habituation. A sex difference in gait ontogeny was observed. The developmental pattern is similar for both sexes, but males increase both SL and SW faster than females. It is proposed that gait topography may yield valuable information in activity studies.

Measurement of atactic and paretic gait in neuropathies of rats based on analysis of walking tracks

In 23 Lewis rats 2 forms of neuropathy both with atactic gait were studied by morphometric analysis of walking tracks. In one group of animals experimental allergic neuritis (EAN) was induced which leads to both sensory and motor dysfunction. Clinical symptoms are atactic gait and hindlimb paresis. In another group pyridoxine (vitamin B6) neuropathy was induced which is a purely sensory neuropathy clinically presenting with gait ataxia, too. Track analysis is a simple method that requires no visualisation process and produces significant and reproducible data. The findings were compared with the clinical scores and electrophysiological data. In EAN, toe spreading was impaired early, and at a later stage stride width, print length and outward rotation of the hind feet changed. Pyridoxine-induced neuropathy produced only an increase in stride width. Track analysis correlated well with clinical grading and electrophysiological recordings. We propose track analysis as a reliable and accurate indicator of neuropathy symptoms in rats.

Subtle abnormalities of gait detected early in vitamin B6 deficiency in aged and weanling rats with hind leg gait analysis

Motor abnormalities have been observed in every species made vitamin B6 deficient, and have been detected and quantified early in vitamin B6 deficiency in young adult female Long-Evans rats with hind leg gait analysis. Our objective was to determine if hind leg gait analysis could be used to detect vitamin B6 deficiency in weanling (3 weeks) and aged (23 months) Fischer 344 male rats. Rats (n = 10 per group) were fed: the control diet ad libitum (AL-CON); the control diet devoid of added pyridoxine hydrochloride (DEF); or the control diet pair-fed to DEF (PF-CON). At 10 weeks, plasma pyridoxal phosphate concentration confirmed deficiency in both age groups. Gait abnormalities were detected in the absence of gross motor disturbances in both aged and weanling DEF rats at 2-3 weeks. Width of step was significantly reduced (16%, p less than 0.003) in DEF aged rats compared to AL- and PF-CON. This pattern of response was similar to that reported previously in young adult rats. In weanling rats, pair feeding alone reduced mean width of step (+/- SEM) by 25% compared to ad libitum feeding (2.7 +/- 0.1 vs 3.6 +/- 0.1 cm for PF- vs AL-CON, respectively, p less than 0.05). In DEF weanling rats, width (3.0 +/- 0.1 cm) was increased compared to PF-CON (11%, p less than 0.05) but decreased compared to AL-CON (16%, p less than 0.05). Width of step was significantly altered early in B6 deficiency in rats of different ages and strains and in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pyrithiamine treatment and subsequent thiamine rehabilitation on regional cerebral amino acids and thiamine-dependent enzymes

Pyrithiamine-induced thiamine-deficiency encephalopathy in the rat shows many neuropathological and biochemical similarities to Wernicke's encephalopathy in humans. Treatment of rats with pyrithiamine resulted in moderate reductions of glutamate in thalamus and pons and in generalized severe reductions of aspartate in pons (by 89%, p less than 0.01), thalamus (by 83%, p less than 0.01), cerebellum (by 53%, p less than 0.01), and cerebral cortex (by 33%, p less than 0.05). Alanine concentrations were concomitantly increased. Activities of the thiamine-dependent enzyme alpha-ketoglutarate dehydrogenase (alpha KGDH) were decreased in parallel with the aspartate decreases; pyruvate dehydrogenase complex activities were unchanged in all brain regions. Following thiamine administration to symptomatic pyrithiamine-treated rats, neurological symptoms were reversed and concentrations of glutamate, aspartate, and alanine, as well as alpha KGDH activities, were restored to normal in cerebral cortex and pons. Aspartate levels and alpha KGDH activities remained below normal values, however, in thalamus. Thus, pyrithiamine treatment leads to reductions of cerebral alpha KGDH and (1) decreased glucose (pyruvate) oxidation resulting in accumulation of alanine and (2) decreased brain content of glutamate and aspartate. Such changes may be of key significance in the pathophysiology of the reversible and irreversible signs of Wernicke's encephalopathy in humans.

Experimental nerve reconnection: importance of initial repair

We believe that the randomness of sprout regrowth is the cause of most poor experimental and clinical functional results after nerve repair. We have elaborated a technique of repair, called "nerve reconnection," aiming to minimize randomness of regrowth. This technique enhances the precision of repair by minimizing physical and chemical damage to the stumps and by ensuring stress-free stump abutment. In this study, the reconnection technique was compared to the conventional microsuture method. First, both techniques were tested as the primary method of repair. A method of behavioral evaluation, the sciatic functional index, was used to assess the results. The reconnection groups consistently showed satisfactory functional results, even after two successive procedures. In contrast, only one-third of the animals in the suture groups reached satisfactory functional levels. In the second part of the study, animals with unsatisfactory results after primary suture were reoperated in an attempt to improve the poor results of initial surgery. The secondary procedures used were either the reconnection technique or conventional microsuture. All secondary procedures failed to improve poor preexisting functional conditions. These findings stress the importance of the original "blueprint" of the nerve and the necessity of maintaining this unique pattern during initial repair.

Reversible alterations of cerebral gamma-aminobutyric acid in pyrithiamine-treated rats: implications for the pathogenesis of Wernicke's encephalopathy

Treatment of rats with the central thiamine antagonist, pyrithiamine, results in severe neurological symptoms such as loss of righting reflex. Measurement of gamma-aminobutyric acid (GABA) content of brain tissue from symptomatic pyrithiamine-treated (PT) rats revealed significant reductions in thalamus, cerebellum, and pons. GABA content of cerebral cortex, however, was unaltered. Activities of the thiamine-dependent enzyme alpha-ketoglutarate dehydrogenase (alpha KGDH) were reduced in parallel with the GABA changes. On the other hand, activities of the GABA-synthetic enzyme glutamic acid decarboxylase (GAD) remained within normal limits, with the exception of a small but significant decrease in thalamus of symptomatic PT rats. Affinities and densities of high-affinity [3H]muscimol binding sites on crude cerebral membrane preparations from symptomatic PT rats were unchanged. Thiamine administration to symptomatic animals resulted in correction of abnormal righting reflexes and in normalization of decreased GABA levels and reduced alpha KGDH activities in cerebellum and pons. Thalamic GABA levels and alpha KGDH activities, on the other hand, remained significantly lower than normal. These results suggest that the reversible symptoms of pyrithiamine treatment may result from imparied GABA synthesis in cerebellum and pons of these animals. Similar mechanisms may play a role in the pathogenesis of the reversible symptoms of Wernicke's encephalopathy in man.

Activities of thiamine-dependent enzymes in two experimental models of thiamine deficiency encephalopathy: 3. Transketolase

Chronic thiamine deprivation in the rat leads to ataxia, loss of righting reflex and neuropathological damage to lateral vestibular nucleus. Before onset of neurological symptoms, transketolase (TK) activities were found to be selectively reduced by 25% in lateral vestibular nucleus and surrounding pons. Further progression of thiamine deprivation resulted in a generalized reduction in TK activity. Measurement of enzyme activity in the presence of added TPP cofactor in vitro did not lead to normalisation of enzyme activities suggesting loss of apoenzyme. Administration of thiamine to symptomatic thiamine-deprived rats resulted in reversal of neurological symptoms and to normalisation of defective TK activities in less vulnerable structures such as cerebral cortex, striatum and hippocampus; reduction of TK activity, however, persisted in brainstem and cerebellar regions. Pyrithiamine treatment results, within 3 weeks, in loss of righting reflex, convulsions and more widespread neuropathological damage compared to that observed following thiamine deprivation. TK activity was found to be significantly decreased before the onset of neurological symptoms in all brain regions and appearance of symptoms was accompanied by more severe reductions of TK. In contrast to chronic thiamine deprivation, TK activities following pyrithiamine treatment were: equally reduced in magnitude in vulnerable and non-vulnerable brain structures, unchanged following reversal of neurological abnormalities by thiamine administration.

Activities of thiamine-dependent enzymes in two experimental models of thiamine-deficiency encephalopathy. 2. alpha-Ketoglutarate dehydrogenase

Chronic thiamine deprivation in the rat leads to selective neuropathological damage to pontine structures. Onset of neurological symptoms of thiamine deprivation (ataxia, loss of righting reflex) was accompanied by selective decreases (of the order of 30%) in the activity of alpha-ketoglutarate dehydrogenase (alpha KGDH) in lateral vestibular nucleus and hypothalamus. Enzyme activities were decreased to a lesser extent in medulla oblongata, striatum and hippocampus and were unchanged in other brain structures. No changes in alpha KGDH occurred prior to the onset of neurological signs of thiamine deprivation. Administration of the central thiamine antagonist, pyrithiamine, results within 3 weeks in loss of righting reflex and convulsions and in more widespread neuropathological changes than those observed following thiamine deprivation. alpha KGDH activities were found to be substantially diminished in all brain regions studied following pyrithiamine treatment with most severe changes occurring in brain regions found to be vulnerable to pyrithiamine (lateral vestibular nucleus, hypothalamus, midbrain, medulla-pons). In some cases, alpha KGDH changes preceded the appearance of neurological symptoms of pyrithiamine treatment. Such decreases in alpha KGDH may explain previous findings of region-selective changes in energy metabolism and of decreased synthesis of glucose-derived neurotransmitters (acetylcholine, GABA, glutamate) in pyrithiamine-treated rat brain. Thiamine administration to symptomatic pyrithiamine treated rats resulted in reversal of neurological signs of encephalopathy and in normalisation of defective alpha KGDH activity in all brain regions. These findings suggest that the reversible neurological symptoms associated with Wernicke's Encephalopathy in man likely result from region-selective impairment of alpha KGDH.

Recovery of function after neonatal or adult hemispherectomy in cats. II. Limb bias and development, paw usage, locomotion and rehabilitative effects of exercise

To investigate the relationship of age-related processes in the recovery of complex motor functions of the limbs, a variety of neurobehavioral assessments were applied to cats with either neonatal (n = 9) or adult (n = 11) removal of the entire left hemitelencephalon (hemispherectomy). Neonatal-lesioned kittens showed no paw preference in reaching for a manipulandum between 5 and 8 weeks of age; thereafter they developed a preference (5.6%) for the unimpaired left limb which persisted throughout adulthood. Adult-lesioned cats showed a significantly greater left bias (13.9%) than neonatal-lesioned cats and they exhibited more abnormal movements and postures when reaching with the impaired limb. Exercising the impaired limb, was effective in reversing the paw preference bias in all lesioned cats. To master a food retrieval task with the impaired limb, adult-lesioned cats required more trials than the neonatal-lesioned group, extensive food deprivation and at least 1 month of postsurgical recovery. However, after mastering this task all cats could continue to perform it indefinitely in their home cages. In a paw print analysis of locomotion, only adult-lesioned cats showed abnormalities including splayed paws, decreased stride length, and adduction of the right hind limb. The results support the 'Kennard Principle' of enhanced recovery following neonatal vs late brain lesions for the present complex motor patterns and are interpreted in the context of neural plasticity and anatomical reorganization during development.

Activities of thiamine-dependent enzymes in two experimental models of thiamine-deficiency encephalopathy: 1. The pyruvate dehydrogenase complex

Chronic thiamine deprivation in the rat leads to selective neuropathological damage in brainstem structures whereas treatment with the central thiamine antagonist, pyrithiamine, results in more widespread damage. In order to further elucidate the neurochemical mechanisms responsible for this selective damage, the thiamine-dependent enzyme complex pyruvate dehydrogenase (PDHC) was measured in 10 brain structures in the rat during progression of thiamine deficiency produced by chronic deprivation or by pyrithiamine treatment. Feeding of a thiamine-deficient diet to adult rats resulted in 5-7 weeks in ataxia and loss of righting reflex accompanied by decreased blood transketolase activities. PDHC activities were selectively decreased by 15-30% in midbrain and pons (lateral vestibular nucleus). Thiamine treatment of symptomatic rats led to reversal of neurological signs and to concomitant reductions of the cerebral PDHC abnormalities. Daily pyrithiamine treatment led within 3 weeks to loss of righting reflex and convulsions and to decreased blood transketolase of a comparable magnitude to that observed in chronic thiamine-deprived rats. No significant regional alterations of PDHC, however, were observed in pyrithiamine-treated rats.

The automated analysis of coordinated hindlimb movement in rats during acute and prolonged exposure to toxic agents

The effects of CNS-active drugs and neurotoxic agents on motor coordination in the rat were studied using a newly developed, automated technique. In this test, a tv/microprocessor-based system was utilized to detect and describe the movement and placement characteristics of one of the rat's hindpaws as the rat placed its paw from one rung to another while walking in a rotating wheel. In studies employing a wheel speed of 8.2 cm/sec and a single 90-sec trial, significant deficits in coordinated hindlimb movement could be detected following the acute ip administration of a variety of compounds, including acrylamide (0, 50, and 100 mg/kg), diazepam (0, 0.5, 1.0, and 2.0 mg/kg), ethyl alcohol (0, 600, 900, and 1200 mg/kg), and tremorine (0, 2.5, 5.0, and 10.0 mg/kg). Further, results from a subacute study involving the oral administration of 2,5-hexanedione (2,5-HD; 0, 250, and 600 mg/kg) indicated that rats treated with 600 mg/kg, 2,5-HD were significantly impaired after 1 week of treatment and those treated with 250 mg/kg 2,5-HD, after 2 weeks of treatment. Although both groups improved during the recovery period, the performance of the 600 mg/kg group 5 weeks post-treatment was still inferior to controls. Taken together, these studies indicate that the coordinated hindlimb placement test provides a reliable, sensitive, and rapid technique for quantifying deficits in motor coordination in the rat during acute and prolonged exposure to neurotoxic substances.

Oxidative metabolism and acetylcholine synthesis during acetylpyridine treatment

In order to clarify the mechanisms by which nicotinic acid deficiency impairs brain function, the effects of the nicotinic acid antimetabolite, 3-acetylpyridine, have been investigated on behavior, cerebral oxidative metabolism, and acetylcholine synthesis. In young rats (21-23 days old), 3-acetylpyridine caused dose- and time-related deficits in behavior, as measured by a neurological scale and by "tight-rope" performance, loss of body weight, and decreased survival. An intermediate dosage decreased cerebral glucose utilization in the inferior olivary nuclei, but increased it in the fastigial, interpositus, red, dentate, vestibular, posterior mamillary, and habenular nuclei. Selective alteration of metabolism was also observed in brain slices from 3-acetylpyridine-treated rats. Although forebrain slices were unaffected, in brainstem slices the synthesis of acetylcholine decreased by 34% with depolarizing (31 mM) concentrations of K+ (P less than 0.05). This dose of 3-acetylpyridine did not deplete the total pool of NAD in any of the 7 brain regions examined. Thus, the nicotinic acid deficiency which results from 3-acetylpyridine treatment appears to be yet another metabolic encephalopathy in which cholinergic systems are impaired.

Amino acid changes in regions of the CNS in relation to function in experimental portal-systemic encephalopathy

Sustained hyperammonemia resulting from portocaval anastomosis (PCA) in the rat, is accompanied by neurological symptoms and reversible morphological changes in brain, the nature and distribution of which suggest selective vulnerability of certain brain structures. The present study was initiated to investigate the effects of increasing CNS ammonia on the distribution of amino acids in regions of the rat brain in relation to the degree of neurological impairment in PCA rats. Four weeks following PCA, rats were administered ammonium acetate (5.2 mmol/kg, i.p.) to precipitate neurological symptoms of encephalopathy which included diminished locomotor activity, loss of hindlimb extension and righting reflexes and ultimately coma. At various stages during the development of encephalopathy, rats were sacrificed and the amino acids glutamine, glutamate and aspartate measured simultaneously, using a sensitive double-isotope dansyl microassay. Homogenates of the following regions of the CNS were assayed: cerebral cortex, hippocampus, striatum, midbrain, hypothalamus, cerebellum, medulla-pons, spinal cord (gray matter) and spinal cord (white matter). Sustained hyperammonemia associated with PCA alone resulted in a non-uniform 2-4 fold increase of glutamine in all regions of the CNS. Glutamate, on the other hand, was selectively increased in striatum and cerebellum, two regions of brain shown to exhibit early morphologically-characterised astrocytic abnormalities in rats with PCA. Onset of severe neurological dysfunction was accompanied by significantly decreased glutamine and glutamate in striatum and cerebellum. Thus, sustained hyperammonemia in association with portocaval shunting results in region-selective effects with respect to glutamine-glutamate metabolism in the CNS.

Automated quantitative analysis of coordinated locomotor behaviour in rats

Disturbances of motor coordination are usually difficult to quantify. Therefore, a method was developed for the automated quantitative analysis of the movements of the dyed paws of stepping rats, registered by a colour TV camera. The signals from the TV-video system were converted by an electronic interface into voltages proportional to the X- and Y-coordinates of the paws, from which a desktop computer calculated the movements of these paws in time and distance. Application 1 analysed the steps of a rat walking in a hollow rotating wheel. The results showed low variability of the walking pattern, the method was insensitive to low doses of alcohol, but was suitable to quantify overt, e.g. neurotoxic, locomotor disturbances or recovery thereof. In application 2 hurdles were placed in a similar hollow wheel and the rats were trained to step from the top of one hurdle to another. Physostigmine-induced disturbances of this acquired complex motor task could be detected at doses far below those that cause overt symptoms.

Neurotensin affects hyperactivity but not stereotypy induced by pre and post synaptic dopaminergic stimulation

The effects of intraventricular administration of neurotensin (0.9, 3.75 and 15.0 micrograms) on hyperactivity and stereotypy induced by either amphetamine (1 mg/kg), nomifensine (20 mg/kg), apomorphine (0.5 mg/kg) or N-n-propylnorapomorphine (0.5 mg/kg) were examined. Results indicate that for each drug treatment, the effects of neurotensin were identical: hyperactivity was significantly reduced while stereotypy remained unaffected. Results also revealed that neurotensin significantly increased the hypothermia induced by apomorphine and N-n-propylnorapomorphine. Possible mechanisms which could underly neurotensin's selective inhibitory action on hyperactivity produced by both pre and post synaptic dopaminergic stimulation are discussed.

Regional amino acid distribution in relation to function in insulin hypoglycaemia

The amino acids glutamate, aspartate, gamma-aminobutyric acid (GABA), and glutamine were measured as their dansyl derivatives in whole brain and specific brain regions by a sensitive double-labelling technique at various times during the development of hypoglycaemic encephalopathy. Hypoglycaemia was induced by administration of insulin (100 i.u./kg) to 24-h fasted rats. No significant changes in glutamate, GABA, or glutamine were detected in whole brain at any time up to and including the onset of hypoglycaemic convulsions. In cerebral cortex, however, GABA levels were reduced to 65% or normal prior to the appearance of neurological symptoms of hypoglycaemia. Onset of symptoms (severe catalepsy and loss of righting reflex, but before the onset of convulsions) was accompanied by marked decreases of glutamate and glutamine in striatum and hippocampus. These regions, in addition to cerebral cortex, show the greatest vulnerability to hypoglycaemic insult, according to previous anatomical studies. Aspartate levels were significantly increased (p less than 0.01) in the cerebral cortex of convulsing animals, confirming a previous report. No changes were detectable in any of the amino acids studied in medulla-pons at any time during the progression of hypoglycaemia. Cerebral cortex and striatum showed a selective net loss of amino acids (2.2 and 3.5 mumol/g. respectively) prior to the onset of insulin-hypoglycaemic convulsions.

Tissue lipids in acute acrylamide intoxicated rats

A preliminary survey of tissue lipid composition in acrylamide intoxicated rats is reported. The animals were injected intraperitoneally with acrylamide 50 mg/kg body weight per day for 10 days. Liver cholesterol, mainly in the ester fraction, was decreased in treated rats. When fatty acid composition of liver cholesterol esters was examined, the proportions of linoleate and stearate were found to be decreased and were compensated by the increase of palmitate. Atrophy of epididymal fat pad resulted in severe triglyceride depletion and a relative increase in the proportion of phospholipids and cholesterol. There was also a reduction of linoleate, palmitate and palmitoleate in triglycerides and phospholipids of this tissue. There were, however, only minor changes in the fatty acid profile of the sciatic nerve.

Glutamate and aspartate do not modify the ataxic gait of acrylamide treated animals

The purpose of this experiment was to examine the effects of intraventricular injections of glutamate and aspartate on the gait of animals rendered ataxic by the administration of acrylamide. Contrary to their previously reported corrective influence on ataxia induced by 3-acetyl pyridine, these amino acids did not modify the ataxic gait of acrylamide treated animals. This suggests that glutamate and aspartate can act in cerebellar but not in peripheral types of ataxia in animals.

Influence of nicotinamide on neurobehavioral effects of 3-acetylpyridine

The purpose of the present study was to examine the ability of nicotinamide to prevent the appearance of neurobehavioral symptoms induced by 3-acetyl pyridine (3-AP) in rats. Nicotinamide in doses of 5,50 and 500 mg/kg was injected immediately after administration of 65 mg/kg 3-AP, and neurobehavioral measurements were made at 6, 12, 24, 48 and 72 hours after injections. The effects of 500 mg/kg nicotinamide injected at 3 and 6 hours after 3-AP treatment were also investigated. The results indicate that, starting at 50 mg/kg, nicotinamide can protect animals against most of the neurobehavioral effects of 3-AP. However, the muscular rigidity induced by 3-AP can only be reversed by 500 mg/kg nicotinamide, and the depressing influence of 3-AP on locomotor activity is not blocked by any of the doses of nicotinamide tested. In terms of time course, the protective action of 500 mg/kg is seen when injected 3, but not 6 hours after 3-AP.

Effects of glutamate and aspartate on ataxic gait induced by 3-acetyl pyridine in rats

The main purpose of this study was to examine the effects of intraventricular injections of glutamate and aspartate on the walking gait of rendered ataxic by the administration of 3-acetyl pyridine. Both amino acids significantly improved the walking gait of these animals. The effects of other substances known to have a stimulatory influence on locomotor activity in rats were also investigated. Amphetamine, apomorphine and thyrotropin releasing hormone (TRH) had no effect on the ataxic gait of 3-AP treated animals. Substance P significantly improved the gait of ataxic animals, but to a lesser extent than that seen with glutamate and aspartate.

Friedreich's ataxia 1980. An overview of the physiopathology

Phase three of the Quebec Cooperative Study of Friedreich's Ataxia was devoted to an understanding of the physiopathology of individual symptoms on the basis of previously discovered biochemical leads. The present paper attempts to pull these results together by presenting, as a hypothesis, a unifying scheme of possible interactions and relationships. The central core of this hypothesis is the demonstration in Friedreich's ataxia of a state of mitochondrial energy deprivation. This is indirectly responsible for such associated and important symptoms as muscle weakness, dying-back neuropathy, scoliosis and hypertrophic cardiomyopathy. Secondarily, and possibly as an independent but linked-event, the entry of glucose into cells and pyruvate oxidation, are slowed down, favoring the development of diabetes. As a consequence, tissue concentrations of glutamic acid and aspartic acid are decreased, particularly in more vulnerable areas such as the cerebellum, brain stem and dorsal root ganglia. This tissue deficiency in putative excitatory neurotransmitters is directly responsible for the symptom of ataxia. This conclusion is reinforced by the correction of the ataxia in experimental animals, by the intraventricular injection of the same amino acids, and not by the injection of other stimulants of motricity. The observed mitochondrial energy deprivation could be the metabolic consequence of major changes in the linoleic acid (18.2) composition of inner mitochondrial membrane phospholipids, such as cardiolipin. Such decreases in membrane 18:2 could be the result of interference with the normal incorporation of this fatty acid to lipoproteins and/or cell membranes. It is at this level that the search for the specific enzyme defect in Friedreich's ataxia is continuing.