The temporal patterns of c-Fos and basic fibroblast growth factor expression following a unilateral anteromedial cortex lesion

The pattern of c-Fos expression and its refractory period in the brain of rats and monkeys

Intense activation of neurons triggers the appearance of immediate expression genes, including c-Fos. This gene is related to various signal cascades involved in biochemical processes such as neuronal plasticity, cell growth and mitosis. Here we investigate the expression pattern and the refractory period of c-Fos in rats and monkey's brains after stimulation with pentylenetetrazol. Rats and monkeys were sacrificed at various times after PTZ-induced seizure. Here we show that rats and monkeys already showed c-Fos expression at 0.5 h after seizure. Yet, the pattern of protein expression was longer in monkeys than rats, and also was not uniform (relative intensity) across different brain regions in monkeys as opposed to rats. In addition monkeys had a regional brain variation with regard to the temporal profile of c-Fos expression, which was not seen in rats. The refractory period after a second PTZ stimulation was also markedly different between rats and monkeys with the latter even showing a summatory effect on c-Fos expression after a second stimulation. However, assessment of c-Fos mRNA in rats indicated a post-transcriptional control mechanism underlying the duration of the refractory period. The difference in the protein expression pattern in rodents and primates characterizes a functional aspect of brain biochemistry that differs between these mammalian orders and may contribute for the more developed primate cognitive complexity as compared to rodents given c-Fos involvement in cognitive and learning tasks.

Biologic and plastic effects of experimental traumatic brain injury treatment paradigms and their relevance to clinical rehabilitation

Neuroplastic changes, whether induced by traumatic brain injury (TBI) or therapeutic interventions, alter neurobehavioral outcome. Here we present several treatment strategies that have been evaluated by using experimental TBI models and discuss potential mechanisms of action (ie, plasticity) and how such changes affect function.

Transient gastric irritation in the neonatal rats leads to changes in hypothalamic CRF expression, depression- and anxiety-like behavior as adults

AIMS

A disturbance of the brain-gut axis is a prominent feature in functional bowel disorders (such as irritable bowel syndrome and functional dyspepsia) and psychological abnormalities are often implicated in their pathogenesis. We hypothesized that psychological morbidity in these conditions may result from gastrointestinal problems, rather than causing them.

METHODS

Functional dyspepsia was induced by neonatal gastric irritation in male rats. 10-day old male Sprague-Dawley rats received 0.1% iodoacetamide (IA) or vehicle by oral gavage for 6 days. At 8-10 weeks of age, rats were tested with sucrose preference and forced-swimming tests to examine depression-like behavior. Elevated plus maze, open field and light-dark box tests were used to test anxiety-like behaviors. ACTH and corticosterone responses to a minor stressor, saline injection, and hypothalamic CRF expression were also measured.

RESULTS

Behavioral tests revealed changes of anxiety- and depression-like behaviors in IA-treated, but not control rats. As compared with controls, hypothalamic and amygdaloid CRF immunoreactivity, basal levels of plasma corticosterone and stress-induced ACTH were significantly higher in IA-treated rats. Gastric sensory ablation with resiniferatoxin had no effect on behaviors but treatment with CRF type 1 receptor antagonist, antalarmin, reversed the depression-like behavior in IA-treated rats

CONCLUSIONS

The present results suggest that transient gastric irritation in the neonatal period can induce a long lasting increase in depression- and anxiety-like behaviors, increased expression of CRF in the hypothalamus, and an increased sensitivity of HPA axis to stress. The depression-like behavior may be mediated by the CRF1 receptor. These findings have significant implications for the pathogenesis of psychological co-morbidity in patients with functional bowel disorders.

Lesion of the ventral tegmental area amplifies stimulation-induced Fos expression in the rat brain

Unilateral lesions of the ventral tegmental area (VTA), the key structure of the mesolimbic system, facilitate behavioral responses induced by electrical stimulation of the VTA in the contralateral hemisphere. In search of the neuronal mechanism behind this phenomenon, Fos expression was used to measure neuronal activation of the target mesolimbic structures in rats subjected to unilateral electrocoagulation and simultaneously to contralateral electrical stimulation of the VTA (L/S group). These were compared to the level of mesolimbic activation after unilateral electrocoagulation of the VTA (L group), unilateral electrical stimulation of the VTA (S group) and bilateral electrode implantation into the VTA in the sham (Sh) group. We found that unilateral stimulation of the VTA alone increased the density of Fos containing neurons in the ipsilateral mesolimbic target structures: nucleus accumbens, lateral septum and amygdala in comparison with the sham group. However, unilateral lesion of the VTA was devoid of effect in non-stimulated (L) rats and it significantly amplified the stimulation-induced Fos-immunoreactivity (L/S vs S group). Stimulation of the VTA performed after contralateral lesion (L/S) evoked strong bilateral induction of Fos expression in the mesolimbic structures involved in motivation and reward (nucleus accumbens and lateral septum) and the processing of the reinforcing properties of olfactory stimuli (anterior cortical amygdaloid nucleus) in parallel with facilitation of behavioral function measured as shortened latency of eating or exploration. Our data suggest that VTA lesion sensitizes mesolimbic system to stimuli by suppressing an inhibitory influence of brain areas afferenting the VTA.

Identification of astrocyte secreted proteins with a combination of shotgun proteomics and bioinformatics

Astrocytes are important regulators of normal brain function in mammals, including roles in synaptic signaling, synapse formation, and neuronal health and survival. Many of these functions are executed via secreted proteins. To analyze the astrocyte secretome, a combination of shotgun proteomics and bioinformatics was employed to analyze conditioned media from primary murine astrocyte cultures. Both two- and one-dimensional LC-MS/MS were used to analyze astrocyte secreted proteins, resulting in the identification of over 420 proteins. To refine our results, the intracellular protein contaminants were removed in silico using a cytoplasmic control. In additional rounds of refinement, putative secreted proteins were subjected to analysis by SignalP, SecretomeP, and gene ontology analysis, yielding a refined list of 187 secreted proteins. In conclusion, the use of shotgun proteomics combined with multiple rounds of data refinement produced a high quality catalog of astrocyte secreted proteins.

Anterior thalamic lesions produce chronic and profuse transcriptional de-regulation in retrosplenial cortex: A model of retrosplenial hypoactivity and covert pathology

Anterior thalamic lesions are thought to produce 'covert pathology' in retrosplenial cortex, but the causes are unknown. Microarray analyses tested the hypothesis that thalamic damage causes a chronic, hypo-function of metabolic and plasticity-related pathways (Experiment 1). Rats with unilateral, anterior thalamic lesions were exposed to a novel environment for 20 minutes, and granular retrosplenial tissue sampled from both hemispheres 30 minutes, 2h, or 8h later. Complementary statistical approaches (analyses of variance, predictive patterning and gene set enrichment analysis) revealed pervasive gene expression differences between retrosplenial cortex ipsilateral to the thalamic lesion and contralateral to the lesion. Selected gene differences were validated by QPCR, immunohistochemistry (Experiment 1), and in situ hybridisation (Experiment 2). Following thalamic lesions, the retrosplenial cortex undergoes profuse cellular transcriptome changes including lower relative levels of specific mRNAs involved in energy metabolism and neuronal plasticity. These changes in functional gene expression may be largely driven by decreases in the expression of multiple transcription factors, including brd8, c-fos, fra-2, klf5, nfix, nr4a1, smad3, smarcc2, and zfp9, with a much smaller number (nfat5, neuroD1, RXRγ) showing increases. These findings have implications for conditions such as diencephalic amnesia and Alzheimer's disease, where both anterior thalamic pathology and retrosplenial cortex hypometabolism are prominent.

Behavioral and immunohistological effects of cholinergic damage in immunolesioned rats: Alteration of c-Fos and polysialylated neural cell adhesion molecule expression

The aim of this study was to determine the brain structures as well as the plasticity events associated with the behavioral effects of cholinergic damage. Rats were submitted to injection of 192 IgG-saporin in the medial septum/diagonal band of Broca complex and the nucleus basalis magnocellularis. The immunohistochemical expression of c-Fos protein and PSA-NCAM (polysialylated neural cell adhesion molecule) and the behavioral performances in the nonmatching-to-position task were assessed at various post-lesion times. Thus, 3 days after injection of the immunotoxin, increased c-Fos labeling was observed in the areas of infusion, indicating these cells were undergoing some plastic changes and/or apoptotic processes. A drastic increase was observed in the number of PSA-NCAM positive cells and in their dendritic arborization in the dentate gyrus. At 7 days post-lesion, no behavioral deficit was observed in immunolesioned rats despite the drastic loss of cholinergic neurons. These neurons showed decreased c-Fos protein expression in the piriform and entorhinal cortex and in the dentate gyrus. In the latter, PSA-NCAM induction was high, suggesting that remodeling occurred, which in turn might contribute to sustaining some mnemonic function in immunolesioned rats. At 1 month, cholinergic neurons totally disappeared and behavioral deficits were drastic. c-Fos expression showed no change. In contrast, the increased PSA-NCAM-labeling observed at short post-lesion times was maintained but the plastic changes due to this molecule could not compensate the behavioral deficit caused by the immunotoxin. Thus, as the post-lesion time increases, a gradual degeneration process should occur that may contribute to mnemonic impairments. This neuronal loss leads to molecular and cellular alterations, which in turn may aggravate cognitive deficits.

Behavioral and neuroplastic effects of focal endothelin-1 induced sensorimotor cortex lesions

Previous studies have established the usefulness of endothelin-1 (ET-1) for the production of focal cerebral ischemia. The present study assessed the behavioral effects of focal ET-1-induced lesions of the sensorimotor cortex (SMC) in adult rats as well as cellular and structural changes in the contralateral homotopic motor cortex at early (2 days) and later (14 days) post-lesion time points. ET-1 lesions resulted in somatosensory and postural-motor impairments in the contralateral (to the lesion) forelimb as assessed on a battery of sensitive measures of sensorimotor function. The lesions also resulted in the development of a hyper-reliance on the ipsilateral forelimb for postural-support behaviors. In comparison to sham-operated rats, in layer V of the motor cortex opposite the lesions, there were time- and laminar-dependent increases in the surface density of dendritic processes immunoreactive for microtubule-associated protein 2, in the optical density of N-methyl-D-asparate receptor (NMDA) subunit 1 immunoreactivity, and in the numerical density of cells immunolabeled for Fos, the protein product of the immediate early gene c-fos. These findings corroborate and extend previous findings of the effects of electrolytic lesions of the SMC. It is likely that compensatory forelimb behavioral changes and transcallosal degeneration play important roles in these changes in the cortex opposite the lesion, similar to previously reported effects of electrolytic SMC lesions.

Propentofylline after focal cortical lesion in the rat: impact on functional recovery and basic fibroblast growth factor expression

The effects of propentofylline, a xanthine derivative and adenosine transport inhibitor, were evaluated following anteromedial cortex lesion in the rat. Propentofylline (2x/10 mg/kg, intraperitoneally) was administered for 7 days post-insult and basic fibroblast growth factor (bFGF) immunoreactivity measured at designated time points in the peri-lesional cortex and ipsilateral dorsal striatum. The spatiotemporal pattern of bFGF expression was then compared to functional recovery patterns. Propentofylline-treated animals displayed increased bFGF expression in the peri-lesional cortex which may have contributed to the observed early facilitation of functional recovery. Drug administration did not, however, produce a change in bFGF expression in the ipsilateral dorsal striatum compared to saline-treated animals. These findings taken together with other positive findings regarding propentofylline, support the drug's therapeutic potential.

Vigabatrin directed against kindled seizures following cortical insult: impact on epileptogenesis and somatosensory recovery

The anticonvulsant drug vigabatrin has not been found to be detrimental to the recovery process when administered following focal cortical insult. This finding is in contrast to the negative postinjury consequences of other anticonvulsant drugs (e.g., phenobarbital and diazepam) with more direct activation of the GABA/benzodiazepine receptor complex. Moreover, phenobarbital directed against kindled seizures affects functional recovery more adversely than either the drug or subconvulsive seizures alone. The purpose of the present study was to determine whether vigabatrin (150, 200, and 250 mg/kg) directed against kindled seizures would impact recovery from lesion-induced somatosensory deficits. Vigabatrin was coupled with daily electrical kindling of the amygdala during the first week after a unilateral anteromedial cortex (AMC) lesion. Somatosensory recovery was assessed using bilateral tactile stimulation tests. Animals receiving the highest dose of vigabatrin prior to electrical kindling (250 mg/kg vigabatrin/kindled) remained significantly impaired even after two months of testing relative to vehicle/kindled, kindled/250 mg/kg vigabatrin, which received vigabatrin after electrical kindling, and the 150, 200, and 250 mg/kg vigabatrin/nonkindled groups (p < 0.0001). In contrast, neither vigabatrin (at any of the doses tested) nor subconvulsive kindled seizures impacted the recovery process (p > 0.05) when administered alone (i.e., without the drug + seizure interaction). These data add to the accumulating experimental and clinical evidence suggesting that the neurobehavioral consequences of the interaction between anticonvulsant drugs and subclinical seizures after brain insult are detrimental to functional recovery.