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PubMed2005

Intracerebral hemorrhage in the iron-deficient rat.

BACKGROUND AND PURPOSE: Iron contributes to brain injury after intracerebral hemorrhage (ICH). Because ICH may occur in the context of iron deficiency anemia (IDA), a common nutritional disorder, the purpose of this study was to determine whether IDA in rats affects brain edema, functional behavior, and changes in brain iron-handling proteins after ICH. METHODS: Six-week-old male rats (n=75) were randomized to non-IDA or IDA groups and provided iron-sufficient or -deficient diets, respectively. After 1 month, 100 microL autologous blood was infused into the right basal ganglia (BG). Brains removed at days 1, 3, 7, and 28 after ICH were assessed for regional brain water content and BG transferrin and transferrin receptor concentrations (Western blotting). Sensorimotor measures of functional recovery were assessed. RESULTS: Brain water content was increased for IDA versus non-IDA in injured cortex and BG at day 3 (P<0.05). IDA rats had impaired left forepaw placing and more asymmetric forelimb use versus non-IDA after ICH (P<0.05). Transferrin and transferrin receptor concentrations in the BG were increased for IDA versus non-IDA within the first week (P<0.05). CONCLUSIONS: Rats with IDA have greater brain edema, poorer sensorimotor outcome, and a greater expression of iron regulatory proteins than non-IDA rats after ICH, suggesting brain iron status is a determinant of injury severity and recovery.

Anemia, Iron-Deficiency↗
PubMed2001

Homotopic grafts of septal neurons combined to polymeric hydrogels placed into a fimbria-fornix lesion cavity attenuate locomotor hyperactivity but not mnemonic dysfunctions in rats.

PURPOSE: We studied the behavioral effects of an intracavitary implantation of poly[N-(2-hydroxypropyl)-methacrylamidel (PHPMA) hydrogels combined to intraseptal grafts of fetal septal cell suspensions in adult female rats subjected to aspirative fimbria-fornix lesions. The hydrogels were used as substrates for bridging the lesion cavity between the septum and the hippocampus. METHODS: Control groups included sham-operated or lesion-only rats, as well as lesioned rats with only the hydrogel bridge in the lesion cavity, only the graft in the septum, or an intrahippocampal graft of a septal cell suspension as a control for the standardly used ectopic transplantation strategy. Up to 10 months after grafting surgery, all rats were tested for locomotor activity in their home cage, sensorimotor performances using a beam-walking test, and cognitive performances in a radial maze, a water maze and a T-maze (rewarded alternation). RESULTS: The lesions induced hyperlocomotion, sensorimotor disturbances and severe alterations of cognitive functions. We found that neither the grafts or the hydrogels, nor the combination of both, induced any significant enhancement of sensorimotor or cognitive performances. Nevertheless, in rats with both intraseptal (homotopic) grafts and a hydrogel implant, the locomotor activity did no longer differ from that found in sham-operated controls. Histological analysis showed that the hydrogels contained acetylcholinesterase(AChE)-positive fibers and that the hippocampal region in contact with the hydrogel exhibited AChE-positive reaction products over several hundreds of micrometers. CONCLUSIONS: These results are complementary to our previous report on electrophysiological evidence of septo-hippocampal reconnections (Duconseille et al., Rest. Neurol. Neurosci. 15, 1999, 305-317). They further suggest that septal neurons grafted homotopically and/or neurons from the host brain are able to elongate axonal processes through a PHPMA substrate up to the hippocampus. Although they did not affect the cognitive consequences of the lesion, the changes enabled by the homotopic grafts combined to the hydrogel have attenuated the lesion-induced hyperactivity.

Animals↗
PubMed1996

Neuropeptide localization in varicosities of Aplysia sensory neurons is regulated by target and neuromodulators evoking long-term synaptic plasticity.

The synapses between the sensory neuron (SN) and motor neuron of Aplysia undergo long-term functional and structural modulation with appropriate behavioral training or with applications of specific neuromodulators. Expression of molecules within the presynaptic terminals may be regulated in parallel with the changes evoked by the neuromodulators. We examined with immunocytochemical methods whether the level of sensorin, the SN-specific neuropeptide, is modulated in SN varicosities by the location of interaction with the target motor cell L7 and by applications of either 5-HT that evoke long-term facilitation or FMRFamide that evoke long-term depression of Aplysia sensorimotor connections in vitro. A significantly higher proportion of SN varicosities are sensorin positive when they are in contact with the proximal axons of L7 compared to varicosities of the same SNs in contact with distal L7 neurites. Both 5-HT and FMRFamide evoked changes in the efficacy and structure of sensorimotor connections that are accompanied by changes in the frequency of sensorin-positive varicosities contacting the axons of L7. More preexisting SN varicosities are stained after 5-HT, and fewer preexisting SN varicosities are stained after FMRFamide. These results suggest that the postsynaptic target and the neuromodulators not only regulate overall structure but also regulate the level of SN neuropeptide at synaptic sites.

Animals↗
PubMed2006

Acquisition of a conditioned avoidance reflex and morphometric characteristics of the sensorimotor cortex in rats subjected to social deprivation in early ontogenesis.

Male Wistar rats were subjected to social deprivation from day 22 to day 70 of postnatal development to form a group of isolants. Measures of learning of a passive avoidance and the results of training to active avoidance of painful electrical stimulation in these rats were significantly lower at age 110-120 days than in control rats. The characteristics of movement activity in isolants during training and testing, as well as in the open field test, probably resulted from their high levels of anxiety. Morphometric measurements of the numbers of neurons, satellite glial cells, and free glial cells in the sensorimotor area of the neocortex showed that isolants had a significantly lower density of neural elements per unit area, which resulted from a decrease in the afferent flow due to social isolation.

Age Factors↗
PubMed1985

Radial maze performance in young and aged mice: neurochemical correlates.

Young (8 month) and aged (27-28 month) male C57BL/6J mice were trained in a spatial discrimination task requiring working memory. The mice were tested during three trials daily in an eight-arm radial maze for 36 test days. Correct choices were reinforced with isotonic saline. In contrast to past reports, young mice learned the task. Old mice also learned the task, and no significant age-related differences in performance were observed. Following maze training, the mice were killed, the brains removed, and the specific activities of choline acetyltransferase (E.C.2.3.1.6., ChAT) and L-glutamic acid decarboxylase (E.C.4.1.1.15., GAD) were assayed in the hippocampus, and in frontal, sensorimotor, and cingulate areas of the cerebral cortex. The activities of these neurotransmitter synthetic enzymes did not differ significantly between young and old mice. Correct responding in the radial maze was positively correlated to ChAT activity in the cingulate cortex and negatively correlated to ChAT activity in the sensorimotor cortex. There was a similar pattern of correlation between performance and regional GAD activity, although none of the correlations involving GAD reached statistical significance.

Aging↗
PubMed2003

Sophisticated spinal contributions to motor control.

The neural circuitry of the spinal cord is capable of solving some of the most complex problems in motor control. Therefore, spinal mechanisms are much more sophisticated than many neuroscientists give them credit for. A key issue in motor control is how sensory inputs direct and inform motor output,--that is, the sensorimotor process. Other major issues involve the actual control of the motor apparatus. In general, there are at least three basic requirements for motor control: the transformations that map information from sensory to motor coordinates, the specification of individual muscle activations to achieve a kinematic goal, and the control of multiple degrees of freedom. Here, we make the case that the vertebrate spinal cord has the capacity to solve each of these problems to a degree that is relevant for normal behavior.

Animals↗
PubMed2003

Brain injury and neurofunctional deficit in neonatal mice with hypoxic-ischemic encephalopathy.

Birth asphyxia accounts for the majority of developmental motor and cognitive deficits. Studies were undertaken to develop a reproducible murine model of perinatal hypoxic-ischemic encephalopathy (HIE) which would permit both anatomic and neurofunctional quantification of injury. Short-term neurofunctional outcomes consisted of three developmental reflexes (righting, cliff aversion and geotaxis) assessed in 7-day-old mouse pups 24 h after unilateral carotid artery ligation followed by inhalation of 8% oxygen. Cerebral infarct volume was dependent on duration of hypoxia, being approximately 2.5-fold greater with longer (60 min) versus shorter (30 min) hypoxia exposure (P=0.001). All three sensorimotor neonatal reflexes assessed at 24 h after HIE injury correlated significantly with long-term neurofunction evaluated using a water-maze test of navigational learning and memory assessed 8 weeks later in the same animals. Cerebral atrophy, a delayed consequence of HIE in this model, also correlated strongly with water-maze performance (r=0.86, P=0.002). These data demonstrate for the first time that murine neonatal sensorimotor reflex performance can be rigorously quantified in the acute phase of perinatal HIE and has strong predictive value not only for anatomic extent of cerebral injury, but also for long-term neurofunctional outcome.

Animals↗
PubMed2006

Restless legs syndrome: a clinical update.

Restless legs syndrome (RLS) is a common and often disabling sensorimotor disorder. Epidemiologic studies suggest that RLS is an underrecognized and undertreated disorder affecting both children and adults. The diagnosis is based primarily on the following four essential criteria: (1) an urge to move, usually associated with paresthesias, (2) onset or exacerbation of symptoms at rest, (3) relief of symptoms with movement, and (4) symptoms manifesting in a circadian pattern. Supplemental workup including polysomnography, iron profile, and/or neuropathy screen can provide support for the diagnosis and aid in the treatment strategy. Behavioral techniques, dopaminergic agents, opiates, benzodiazepines, and antiepileptics all have potential value in treating this disorder. Dopaminergic agents continue to be the most effective RLS treatment. However, due to their potential long-term side effects, these agents should not be considered the sole treatment of choice. In the end, the therapeutic plan should be individualized to suit each patient's presentation and needs.

Behavior Therapy↗
PubMed2000

The role of glutamate receptors in antipsychotic drug action.

It has recently been postulated that disturbances in glutamatergic neurotransmission may contribute to the pathophysiology of schizophrenia. Therefore the aim of the present study was to evaluate the role of glutamate NMDA and group II metabotropic receptors in the antipsychotic drug action. To this aim the influence of some well-known neuroleptics on cortical NMDA receptors was examined. Furthermore, their behavioral effects were compared with those of the novel agonist of group II glutamate metabotropic receptors, LY 354740, in some animal models of schizophrenic deficits. We found that long-term administration of the typical neuroleptic haloperidol and the atypical one clozapine increased the number of NMDA receptors labelled with [3H]CGP 39653 in different cortical areas. Long-, but not short-term, treatment with haloperidol and raclopride diminished the deficit of prepulse inhibition produced by phencyclidine, which is a model of sensorimotor gating deficit in schizophrenia. In contrast, neither short- nor long-term treatment with clozapine influenced the phencyclidine effect in that model. Acute treatment with LY 354740 reversed neither (1) the deficit of prepulse inhibition produced by phencyclidine or apomorphine, nor (2) the impairment in a delayed alternation task induced by MK-801, which is commonly used to model the frontal lobe deficits associated with schizophrenia. The present study suggests that an increase in the density of cortical NMDA receptors may be important to a longterm neuroleptic therapy. Conversely, the results do not support the role of group II metabotropic glutamate receptors in the antipsychotic drug action.

2-Amino-5-phosphonovalerate↗
PubMed2002

Tauroursodeoxycholic acid, a bile acid, is neuroprotective in a transgenic animal model of Huntington's disease.

Huntington's disease (HD) is an untreatable neurological disorder caused by selective and progressive degeneration of the caudate nucleus and putamen of the basal ganglia. Although the etiology of HD pathology is not fully understood, the observed loss of neuronal cells is thought to occur primarily through apoptosis. Furthermore, there is evidence in HD that cell death is mediated through mitochondrial pathways, and mitochondrial deficits are commonly associated with HD. We have previously reported that treatment with tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, prevented neuropathology and associated behavioral deficits in the 3-nitropropionic acid rat model of HD. We therefore examined whether TUDCA would also be neuroprotective in a genetic mouse model of HD. Our results showed that systemically administered TUDCA led to a significant reduction in striatal neuropathology of the R6/2 transgenic HD mouse. Specifically, R6/2 mice began receiving TUDCA at 6 weeks of age and exhibited reduced striatal atrophy, decreased striatal apoptosis, as well as fewer and smaller size ubiquitinated neuronal intranuclear huntingtin inclusions. Moreover, locomotor and sensorimotor deficits were significantly improved in the TUDCA-treated mice. In conclusion, TUDCA is a nontoxic, endogenously produced hydrophilic bile acid that is neuroprotective in a transgenic mouse model of HD and, therefore, may provide a novel and effective treatment in patients with HD.

Animals↗
PubMed2005

Working memory deficits in retinoid X receptor gamma-deficient mice.

Retinoid signaling has been recently shown to be required for mnemonic functions in rodents. To dissect the behavioral and molecular mechanisms involved in this requirement, we have analyzed the spatial and recognition working memory in mice carrying null mutations of retinoid receptors RARbeta and RXRgamma. Double mutants appeared deficient in spatial working memory as tested in spontaneous alternation in the Y-maze and delayed nonmatch to place (DNMTP) test in the T-maze. These mutant mice did acquire, however, spatial place reference or right/left discrimination tasks in the T-maze set-up, indicating that basic sensorimotor functions, spatial orientation, and motivational factors are unlikely to account for deficits in working memory-sensitive tasks. Double-mutant mice were also deficient in novel object recognition at intermediate, but not short delays. RXRgamma appeared to be the functionally predominant receptor in modulation of the working memory, as RXRgamma, but not RARbeta single null mutant mice exhibited deficits similar to those observed in the double mutants. The mechanism of this modulation is potentially related to functions of RXRgamma in frontal and perirhinal cortex, structures in which we detected RXRgamma expression and which are functionally implicated in working memory processes.

Animals↗
PubMed2004

Lack of the metabotropic glutamate receptor subtype 7 selectively impairs short-term working memory but not long-term memory.

Metabotropic glutamate receptors (mGluRs), and in particular the mGluR group III receptors (subtypes 4, 6, 7, 8) are known to play a role in synaptic plasticity and learning. Here, we report the effect of mGluR7 gene ablation in different learning paradigms. In the acoustic startle response (ASR), no differences were seen between knockout (KO) mice and wildtype (WT) littermates in parameters including prepulse inhibition and habituation. In an open field test, no differences were seen between genotypes in motor activity, exploratory behaviour, and fearful behaviour. In a T-maze reinforced alternation working memory (WM) task, again no difference was seen between groups. However, when increasing the demands on working-memory in a 4-arm and 8-arm maze task, KO mice committed more WM errors than WT littermates thereby uncovering a highly significant difference between the two groups that persisted every day for the whole 9 days of the experiment. In a 4-arm maze with 2 arms baited, KO and wildtype mice committed the same number of LTM errors, whereas KOs committed more WM errors. Altogether, these findings suggest that a lack of mGluR7 mainly impairs short-term working but not long-term memory performance while having no effect on sensorimotor processing, non-associative learning, motor activity and spatial orientation. The effects on WM are task-dependent and become apparent in more complex but not simple learning tasks. We discuss how mGluR7 could influence WM.

Animals↗
PubMed1986

Variant and invariant characteristics of speech movements.

Upper lip, lower lip, and jaw kinematics during select speech behaviors were studied in an attempt to identify potential invariant characteristics associated with this highly skilled motor behavior. Data indicated that speech motor actions are executed and planned presumably in terms of relatively invariant combined multimovement gestures. In contrast, the individual upper lip, lower lip, and jaw movements and their moment-to-moment coordination were executed in a variable manner, demonstrating substantial motor equivalence. Based on the trial-to-trial variability in the movement amplitudes, absolute positions, and velocities of the upper lip, lower lip, and jaw, it appears that speech motor planning is not formulated in terms of spatial coordinates. Seemingly, object-level planning for speech may be encoded in relation to the acoustic consequences of the movements and ultimately with regard to listener's auditory perceptions. In addition, certain temporal parameters among the three movements (relative times of movement onsets and velocity peaks) were related stereotypically, reflecting invariances characteristic of more automatic motor behaviors such as chewing and locomotion. These data thus appear to provide some additional insights into the hierarchy of multimovement control. At the top of the motor control hierarchy, the overall plan appears to be generated with explicit specification of certain temporal parameters. Subsequently, based upon the plan and within that stereotypic temporal framework, covariable adjustments among the individual movements are implemented. Given the results of previous perturbation studies, it is hypothesized that these covariable velocity and amplitude adjustments reflect the action of sensorimotor mechanisms.

Adult↗
PubMed2001

Chronic intracerebroventricular exposure to beta-amyloid(1-40) impairs object recognition but does not affect spontaneous locomotor activity or sensorimotor gating in the rat.

This study examined the cognitive effects of chronic in vivo exposure to beta-amyloid(1-40) via the intracerebroventricular route on two distinct paradigms. The first test evaluated a form of early attentional control referred to as sensorimotor gating in which an antecedent weak prepulse stimulus modulates the reactivity to a subsequent startle-eliciting stimulus. The second test utilized the spontaneous preference for a novel object over that of a familiar one in rats as a measure of object recognition memory. We found that beta-amyloid exposure leads to a severe deficit in the object memory test but spares sensorimotor gating. Moreover, unlike the water maze deficit induced by beta-amyloid (Nag et al., in preparation), the deficit on object recognition was resistant to amelioration by systemic physostigmine treatment at a dose of 0.06 mg/kg per day intraperitoneally. The present results add to previous reports that beta-amyloid exposure can lead to deficits on hippocampal lesion sensitive tasks, suggesting that dysfunction of the rhinal cortices in addition to that of the septohippocampal system is implicated in beta-amyloid-induced behavioral impairments. It therefore lends support to the hypothesis that beta-amyloid exposure can lead to severe impairment across multiple memory systems.

Acoustic Stimulation↗
PubMed1992

Comparison of screening approaches.

Neurobehavioral techniques have been used extensively in animal toxicology studies because, in many cases, such procedures are designed to evaluate neurobiological functions thought to be affected in chemical-exposed humans, e.g., changes in sensorimotor function. Procedures used to identify or screen for the presence of neurotoxicity are usually designed to test large numbers of animals and are not considered to be as sensitive to subtle effects as more specialized tests for neurobiological dysfunction. For purposes of screening, the use of a functional observational battery (FOB) is now generally accepted. In general, FOB evaluations in animals are similar to clinical neurological examinations in humans in that they rate the presence and, in some cases, the severity of behavioral and neurological signs. A number of batteries containing different observations and measurements have been developed in several laboratories for rodents, dogs, and non-human primates. Frequently, the FOB is used in conjunction with other measures of neurotoxicity, i.e., neuropathology or sensory evoked potentials. FOB used in screening typically assess several neurobiological domains including neuromuscular (i.e., weakness, incoordination, abnormal movements, gait, motor seizures, myoclonia, rigidity and tremor), sensory (i.e., auditory, visual and somatosensory) and autonomic (i.e., pupil response, salivation) functions. Most FOB used for screening do not assess cognitive function (i.e., learning and memory). FOB evaluations can yield important information concerning dose-response characteristics and data on the onset, duration and persistence of an effect. FOB should be able to differentiate neurotoxicants from non-neurotoxicants and neurotoxicants having different mechanism(s) or site(s) of action.

Animals↗
PubMed2000

Prominence of direct entorhinal-CA1 pathway activation in sensorimotor and cognitive tasks revealed by 2-DG functional mapping in nonhuman primate.

The trisynaptic pathway from entorhinal cortex to the hippocampus has long been regarded as the major route of information transfer underlying memory consolidation. Most physiological studies of this pathway involve recording from hippocampal slices. We have used both single- and double-label 2-deoxyglucose autoradiographic methods to image the pattern of activation in the hippocampal formation of 14 rhesus monkeys performing cognitive tasks, varying in content (spatial or nonspatial), process (working memory or associative memory), and mode of response (oculomotor or manual). These studies revealed a highly differentiated pattern of metabolic activation throughout the rostrocaudal extent of the hippocampal formation that was common to all behavioral conditions examined. This pattern consisted of intense activation of the stratum lacunosum-moleculare of CA1 and the subiculum, contrasting with barely detectable activity in CA3 and modest activation in the dentate gyrus, which did not include its molecular layer. These findings indicate a remarkable invariance in hippocampal activation under conditions of varied content, varied process, and varied mode of response and an heretofore-unappreciated preferential engagement of the direct rather than the trisynaptic pathway during performance of a wide range of behavioral tasks.

Animals↗
PubMed1995

Alterations in intracellular calcium chelation reproduce developmental differences in repetitive firing and afterhyperpolarizations in rat neocortical neurons.

Many 1-week-old rat sensorimotor cortical neurons exhibit extreme spike-frequency adaptation (neurons only fire for the first 100-250 ms of a 1 s current injection) accompanied by a large, prolonged afterhyperpolarization (AHP). Relatively greater expression of a Ca-dependent K+ current appears to underlie the extreme adaptation observed in immature cells. In the present study, we examined whether altering intracellular Ca2+ buffering by introducing Ca2+ chelators via the recording electrode could reproduce the age-related differences in firing and AHPs. We studied firing behavior and AHPs in 1-week-old and adult neocortical neurons with sharp microelectrodes, under three recording conditions: no chelator, 2 mM BAPTA, or 100-200 mM BAPTA. Our principal findings in regard to firing behavior and AHPs were that (1) adult-low BAPTA neurons mimicked 1 week-control cells, (2) 1 week-high BAPTA neurons were similar to adult-control cells, (3) a greater percentage of 1 week-low BAPTA neurons showed complete adaptation, and (4) adult neurons impaled with high BAPTA electrodes fired in a burst-spiking mode. These data suggest that Ca2+ regulation is qualitatively different in immature and adult neurons.

Action Potentials↗
PubMed2004

Course of motor recovery following ventrolateral spinal cord injury in the rat.

The purpose of this study was to determine the importance of the pathways running in the ventrolateral spinal funiculus for overground locomotion in adult, freely behaving rats. Left-sided ventrolateral cervical spinal cord injury was performed in adult female Long-Evans rats. The behavioural abilities of these animals were analyzed at 2 days, and weekly for up to 5.5 weeks following spinal cord injury. Behavioural testing consisted of Von Frey filament testing, ladder walking, a paw usage task, and the assessment of ground reaction forces during unrestrained trotting. Animals with injury to the left ventrolateral cervical spinal cord did not develop enhanced sensitivity to pedal mechanical stimulation. At 2 days following injury, animals had impaired skilled locomotion as indicated by increased number of footslips during ladder walking. At 2 days, these animals also used both limbs together more often for support while rearing, while using the forelimb ipsilateral to the injury less than did uninjured animals. Ground reaction force determination revealed that animals tend to bear less weight on the forelimb and hindlimb ipsilateral to the spinal cord injury 2 days after injury. All animals recovered normal or near normal sensorimotor abilities although subtle asymmetries in ground reaction forces were detectable at 5.5 weeks following spinal cord injury. These results suggest that axons in the ventrolateral spinal funiculi contribute to limb movements during exploration and locomotion but their roles can be served by other pathways after ventrolateral spinal injury.

Animals↗