The catechol-o-methyltransferase ValMet polymorphism modulates organization of regional cerebral blood flow response to working memory in adults

This study examined the effect of catechol-o-methyltransferase (COMT) Val¹⁵⁸Met genotypes on the co-activation of brain areas involved in cognition during a working memory (WM) task. The pattern of concomitant region of interest (ROI) activation during WM performance varied by genotype: Val/Val showing the least and Met/Met the most covariance. There were no differences of performance on the WM task between the COMT genotypes. However, relatively better performance was associated with less concomitance of dorsolateral prefrontal cortex (DLPFC) and cingulate cortex for Val/Val, but more concomitance of DLPFC with AH for Met/Met. Within genotypes WM performance was significantly correlated with rCBF to the amygdala/hippocampus (AH) for Val/Val (r = 0.44, p = 0.009), to the parietal lobe for Val/Met (r = 0.29, p = 0.03), and to the thalamus for Met/Met (r = 0.32, p = 0.04). Different genotypes showed different regional specificity and concomitant activation patterns suggesting that varying dopamine availability induces different brain processing pathways to achieve similar WM performance.     

Corticotropin-releasing factor antagonist reduces activation of noradrenalin and serotonin neurons in the locus coeruleus and dorsal raphe in the arousal response accompanied by yawning behavior in rats

We previously reported that intracerebroventricular (icv) administration of corticotropin-releasing factor (CRF) antagonist attenuates the arousal response during yawning behavior in rats. However, the CRF-related pathway involved in the arousal response during yawning is still unclear. In the present study, we assessed the involvement of the CRF-containing pathway from the hypothalamic paraventricular nucleus (PVN) to the locus coeruleus (LC) and the dorsal raphe nucleus (DRN) in the arousal response during frequent spontaneous yawning, which was induced by several microinjections of l-glutamate into the PVN in anesthetized rats, using c-Fos immunohistochemistry. The PVN stimulation showed significant increases in activation of PVN CRF neurons, LC noradrenalin (NA) neurons and DRN serotonin (5-HT) neurons as well as arousal response during yawning. But icv administration of a CRF receptor antagonist, α-helical CRF (9-41), significantly inhibited the activation of both LC NA neurons and DRN 5-HT neurons except the activation of CRF neurons in the PVN, and significantly suppressed the arousal response during yawning. These results suggest that the CRF-containing pathway from PVN CRF neurons to LC NA neurons and DRN 5-HT neurons can be involved in the arousal response during yawning behavior.     

Moderate noise induced cognition impairment of mice and its underlying mechanisms

Noise pollution is recognized as a serious human health problem in modern society. The aim of the present study was to explore the effects of moderate-intensity white noise exposure on learning and memory of mice, and the underlying mechanisms. The learning and memory ability of mice were evaluated by water maze and step-down inhibitory avoidance experiments respectively, following 1, 3, and 6 weeks noise exposure (80 dB SPL, 2 h/day). To explore potential mechanisms, we determined levels of oxidative stress in the inferior colliculus (IC), auditory cortex (AC), and hippocampus (the structures comprising the critical encephalic region associated with the acoustic lemniscal ascending pathway), the phosphorylation of microtubule-associated protein tau in the hippocampus (important role in learning and memory), and the basic auditory response properties of neurons in the IC. Moderate-intensity noise exposure impaired the learning and memory ability of mice in both water maze and step-down inhibitory avoidance experiments, and the longer the noise exposure time the greater the impairment. At 6 weeks after noise exposure, there was also evidence of oxidative damage in the IC, AC, and hippocampus, hyperphosphorylated tau protein in the hippocampus, and significant changes in the auditory response properties of neurons in the IC. These data results suggest that moderate-intensity noise can progressively impair the learning and memory ability of mice, which may result from peroxidative damage, tau hyperphosphorylation, and auditory coding alteration.     

Working memory impairment and reduced hippocampal and prefrontal cortex c-Fos expression in a rat model of cirrhosis

Hepatic encephalopathy (HE) is a frequent neurological complication observed in patients with liver malfunction. Previous studies have shown memory impairment in these patients. In order to investigate brain substrates of spatial working memory impairment in chronic HE, neuronal expression of c-Fos protein was studied in an experimental model of cirrhosis. Control and cirrhotic rats were trained on a spatial working memory task in the Morris water maze (MWM). Differences between groups were found in the working memory task. Cirrhotic rats were unable to locate the platform in the retention trial. Neuronal activation, measured by c-Fos protein, was compared between groups. No differences were found in c-Fos expression of control and cirrhotic rats that were not tested in the MWM. Working memory task produced increase in c-Fos positive cells in dorsal hippocampus, CA1 and CA3, and prefrontal cortex in control group compared to thioacetamide group or naïve, which only swam in the maze during a similar time. These findings suggest that cirrhotic rats show spatial working memory impairment that could be linked to dysfunction in neuronal activity in prefrontal cortex and hippocampus.     

Disinhibition of the prefrontal cortex leads to brain-wide increases in neuronal activation that are modified by spatial learning

Deficient prefrontal cortex (PFC) GABA function is hypothesized to play a role in schizophrenia and other psychiatric disorders. In rodents, PFC GABA_A receptor antagonism produces cognitive and behavioral changes relevant to these disorders, including impaired spatial memory assessed with the traditional working/reference memory radial maze task. This aspect of spatial memory does not depend on PFC, suggesting that deficient PFC GABAergic transmission may interfere with non-PFC-dependent cognitive functions via aberrant increases in PFC output. To test this, we assessed whether PFC GABA_A antagonism (50 ng bicuculline methbromide) alters neuronal activation in PFC terminal regions, including the striatum, thalamus, hippocampus, amygdala, and cortical regions, of adult male rats using the immediate early gene, c-Fos, as an activity marker. A subset of these animals were also trained and/or tested on the working/reference memory radial maze task. These treatments caused widespread increases in neuronal activation in animals under baseline conditions, with notable exception of the hippocampus. Furthermore, PFC GABA_A antagonism impaired task performance. In most instances, training and/or testing on the radial maze had no additional effects on neuronal activation. However, in both the hippocampus and rhomboid thalamic nucleus, PFC GABA_A antagonism caused a selective increase in neuronal activation in animals trained on the maze. These results indicate that deficiencies in PFC GABAergic transmission may have widespread impacts on neuronal activity that may interfere with certain PFC-independent cognitive functions. Furthermore, these alterations in activity are modulated by plasticity induced by spatial learning in the hippocampus and rhomboid thalamic nucleus.

     

不同张力扩张子宫颈诱导大鼠延髓内脏带c-Fos及神经型一氧化氮合酶的表达变化

目的观察不同张力扩张子宫颈(UCD)诱导大鼠延髓内脏带神经元c-Fos和神经型一氧化氮合酶(n NOS)的表达变化,探讨UCD疼痛在延髓水平的传导机制。方法成年雌性SD大鼠随机分为对照组(UCD 0g)、宫颈扩张50g张力组(UCD 50g)和宫颈扩张100g张力组(UCD 100g)。UCD组大鼠实施50g及100g张力扩张刺激,UCD刺激后2h,取延髓组织采用还原型辅酶Ⅱ(NADPH)组织化学和c-Fos免疫组织化学双重染色法观察c-Fos、n NOS和c-Fos/n NOS阳性神经元的分布,Western blotting和Real-time PCR法分别检测c-Fos及n NOS蛋白和mRNA水平。结果 c-Fos免疫阳性神经元的细胞核为棕黄色,呈圆形或卵圆形,胞质不着色。n NOS阳性神经元的胞体和突起呈蓝色,胞核不着色,呈空泡状。c-Fos/n NOS双标神经元的胞体和树突染成蓝色,细胞核呈棕黄色,这些神经元主要分布于延髓孤束核(NTS)和外侧网状核(LRN)内。与UCD 0g组相比,UCD 50g组和UCD 100g组大鼠NTS和LRN内c-Fos、n NOS以及c-Fos/n NOS阳性神经元数量明显增加,染色明显加深,c-Fos、n NOS蛋白及mRNA水平均明显升高(P0.01)。结论大鼠急性UCD可导致NTS和LRN神经元c-Fos及n NOS张力依赖性表达增加,NTS和LRN内的n NOS阳性神经元可能参与UCD疼痛在延髓水平的传导。     

Fos expression and task-related neuronal activity in rat cerebral cortex after instrumental learning

Learning has been shown to induce changes in neuronal gene expression and to produce development of task-specific neuronal activity. The connection between these two features of neuronal plasticity remains of a great interest. To address this issue we compared distribution of c-Fos expressing and task-related neurons in the rat cerebral cortex following instrumental learning of appetitive lever-press task. The number of Fos-positive neurons was determined immunohistochemically in the retrosplenial and the motor cortex of naive ("control" group), newly trained ("acquisition" group) and overtrained ("performance" group) animals. A significant activation of c-Fos expression was observed in the neurons of the retrosplenial but not motor cortex in the "acquisition" group rats, as compared with the "control" and "performance" groups. In accordance with this c-Fos expression difference, the retrosplenial cortex of the trained animals contained significantly more neurons with lever-press-related activity than the motor cortex. Therefore, the two examined cortical areas showed a parallel between experience-dependent induction of c-Fos and development of task-related neuronal activity. These data support a notion that learning-induced activation of c-Fos is associated with long-term neurophysiological changes produced by training.     

c-Fos expression in the visual system of the tree shrew (Tupaia belangeri)

c-Fos is a nuclear phosphoprotein coded by the proto-oncogen c-fos which can be detected immunohistochemically after both physiological and pathological stimuli. This property is of great importance, because it offers a valuable tool for morphofunctional identification of activated neurons. We have studied the neuronal activity in the visual pathway of Tupaia belangeri within the following anatomical structures: retina, superior colliculus (SC), dorsal lateral geniculate nucleus (dLGN), pulvinar (Pu), parabigeminal (PBG) nucleus and primary visual cortex (V1) analyzing the c-Fos expression after exposing the tree shrews to different light stimuli (white light –control positive group–, green light, blue light and darkness conditions –control negative group–). Our findings suggest that in the retina, the ganglion cells and the cells of the inner nuclear layer respond better to blue and green light stimuli, when comparing the c-Fos expression between white, green, blue lights and darkness conditions. However, in the SC, dLGN, Pu, PBG nucleus and V1 another pattern of c-Fos expression is observed: a maximum expression for the control positive group, a minimum expression for the control negative group and intermediate expressions within the blue and green light groups. Conclusion: the expression levels of c-Fos protein are able to show significant differences between distinct light stimuli in all anatomical structures studied (retina, SC, dLGN, Pu, PBG and V1) of T. belangeri.     

c-Fos expression in the supraoptic nucleus is the most intense during different durations of restraint water-immersion stress in the rat

Restraint water-immersion stress (RWIS) can induce anxiety, hypothermia, and severe vagally-mediated gastric dysfunction. The present work explored the effects of different durations of RWIS on neuronal activities of the forebrain by c-Fos expression in conscious rats exposed to RWIS for 0, 30, 60, 120, or 180 min. The peak of c-Fos induction was distinct for different forebrain regions. The most intense c-Fos induction was always observed in the supraoptic nucleus (SON), and then in the hypothalamic paraventricular nucleus (PVN), posterior cortical amygdaloid nucleus (PCoA), central amygdaloid nucleus (CeA), and medial prefrontal cortex (mPFC). Moreover, body temperature was reduced to the lowest degree after 60 min of RWIS, and the gastric lesions tended to gradually worsen with the prolonging of RWIS duration. These data strongly suggest that these nuclei participate in the organismal response to RWIS to different degrees, and may be involved in the hypothermia and gastric lesions induced by RWIS.     

Dorsal raphe nucleus and locus coeruleus neural networks and the elaboration of the sweet-substance-induced antinociception

In order to investigate the effects of monoaminergic neurons of the dorsal raphe nucleus (DRN) and locus coeruleus (LC) on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180–200 g received sucrose solution (250 g/L) for 7–14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of ibotenic acid (1.0 μg/0.2 μL) in the DRN or in the LC. The tail withdrawal latencies of the rats in the tail-flick test were measured immediately before and 7 days after this treatment. The neurochemical lesion of locus coeruleus, but not of DRN neural networks with ibotenic acid, after the chronic intake of sweetened solution, decreased the sweet-substance-induced antinociception. These results indicate the involvement of noradrenaline-containing neurons of the LC in the sucrose-induced antinociception. We also consider the possibility of DRN serotonergic neurons exerting some inhibitory effect on the LC neural networks involved with the elaboration of the sweet-substance-induced antinociception.     

c-Fos expression after deep brain stimulation of the pedunculopontine tegmental nucleus in the rat 6-hydroxydopamine Parkinson model

Deep brain stimulation (DBS) is used to alleviate motor dysfunction in Parkinson's disease (PD). The pedunculopontine nucleus (PPN) may be a potential target for severe freezing and postural instability with 25 Hz stimulation being considered more effective than 130 Hz stimulation. Here we evaluated the expression of c-Fos after 25 Hz and 130 Hz DBS of the pedunculopontine tegmental nucleus (PPTg, i.e., the rodent equivalent to the human PPN) in the rat 6-hydroxydopamine (6-OHDA) PD model.Anaesthetized male Sprague Dawley rats with unilateral 6-OHDA-induced nigrostriatal lesions were stimulated with 25 Hz, 130 Hz, or 0 Hz sham-stimulation for 4 h by electrodes implanted into the ipsilateral PPTg. Thereafter the distribution and number of neurons expressing the immediate early gene c-Fos, a marker for acute neuronal activity, was assessed.DBS of the PPTg induced strong ipsilateral c-Fos expression at the stimulation site, with 25 Hz having a more marked impact than 130 Hz. Additionally, c-Fos was strongly expressed in the central gray. In the dorsal part expression was stronger after 25 Hz stimulation, while in the medial and ventral part there was no difference between 25 Hz and 130 Hz stimulation. Expression in the basal ganglia was negligible.In the rat 6-OHDA PD model stimulation of the PPTg did not affect c-Fos expression in the basal ganglia, but had a strong impact on other functional circuitries. PPN stimulation in humans might therefore also have an impact on other systems than the motor system.     

Inflammation of temporomandibular joint increases neural activity in rat vestibular nucleus

To determine whether the vestibular nuclei are affected by inflammation of temporomandibular joint (TMJ) region, we studied vestibular nucleus neural activity using two experimental groups: (1) normal saline 0.1 cm³ injection at right TMJ region, (2) 10% formalin 0.1 cm³ injection at right TMJ region. Neural activity after 24 hours was assessed by immunohistochemical staining with free-floating section at the level of interaural −1.30 mm to −2.00 mm for c-Fos. In inflammation group, formalin injection produced a bilateral increase in c-Fos at vestibular nucleus with ipsilesional side higher activity. In control group, expression of c-Fos protein was also observed in the vestibular nucleus (VN), especially MVN. But stain intensity of Fos-positive neurons was much weaker and mean number of c-Fos positive cells was fewer than inflammation group. This result suggests that there is a close neural connection between TMJ and vestibular nucleus, especially in case of inflammation.     

Involvement of oxytocin and its receptor in nociceptive modulation in the central nucleus of amygdala of rats

Studies have demonstrated that oxytocin plays important roles in pain modulation in the central nervous system. Oxytocin-ergic neurons are found in paraventricular nucleus and supraoptic nucleus of the hypothalamus. The oxytocin-ergic neurons send fibers from hypothalamus to amygdala and high density of oxytocin receptors are found in the central nucleus of amygdala (CeA). The present study was performed to investigate the influences of oxytocin and its receptors on nociceptive responses in the CeA of rats. Intra-CeA injection of 0.1, 0.5 or 1 nmol of oxytocin induced dose-dependent increases in the handpaw withdrawal latency induced by noxious thermal and mechanical stimulation in rats. The oxytocin-induced anti-nociception could be blocked by the selective oxytocin antagonist 1-deamino-2-d-Tyr-(Oet)-4-Thr-8-Orn-oxytocin. The present study demonstrated that oxytocin and its receptors are involved in nociceptive modulation in the CeA of rats.     

Coordinate regulation of noradrenergic and serotonergic brain regions by amygdalar neurons

Based on the importance of the locus coeruleus-norepinephrine (LC-NE) system and the dorsal raphe nucleus-serotonergic (DRN-5-HT) system in stress-related pathologies, additional understanding of brain regions coordinating their activity is of particular interest. One such candidate is the amygdalar complex, and specifically, the central nucleus (CeA), which has been implicated in emotional arousal and is known to send monosynaptic afferent projections to both these regions. Our present data using dual retrograde tract tracing is the first to demonstrate a population of amygdalar neurons that project in a collateralized manner to the LC and DRN, indicating that amygdalar neurons are positioned to coordinately regulate the LC and DRN, and links these brain regions by virtue of a common set of afferents. Further, we have also characterized the phenotype of a population of these collaterally projecting neurons from the amygdala as containing corticotropin releasing factor or dynorphin, two peptides heavily implicated in the stress response. Understanding the co-regulatory influences of this limbic region on 5HT and NE regions may help fill a gap in our knowledge regarding neural circuits impacting these systems and their adaptations in stress.     

The effects of glycine transporter I inhibitor,N-methylglycine (sarcosine), on ketamine-induced alterations in sensorimotor gating and regional brain c-Fos expression in rats

Reduced N-methyl-d-aspartate receptor (NMDAR) function may contribute to the pathogenesis of schizophrenia. Sarcosine, a potent glycine transporter inhibitor, can increase synaptic glycine and then promote NMDAR function. We assessed the antipsychotic potential of sarcosine by comparing the abilities of sarcosine and clozapine to restore the prepulse inhibition (PPI) deficit, hyperlocomotion and regional brain c-Fos expression changes caused by an NMDAR antagonist, ketamine. Four groups of rats were given acute injections, including saline + saline, saline + 30 mg/kg ketamine, 100 mg/kg sarcosine + 30 mg/kg ketamine, and 15 mg/kg clozapine + 30 mg/kg ketamine. Both sarcosine and clozapine reversed the ketamine-induced PPI deficit and hyperlocomotion. They both did not change ketamine-induced increase in c-Fos expression in the prefrontal cortex and nucleus accumbens. However, in the olfactory bulb, sarcosine, but not clozapine, significantly reduced the ketamine-induced increase in c-Fos expression. Our animal study demonstrated that sarcosine may have antipsychotic potential.     

Spatiotemporal characteristics of pain-associated neuronal activities in primary somatosensory cortex induced by peripheral persistent nociception

The primary somatosensory cortex (S1 area) is one of the key brain structures for central processing of somatic noxious information to produce pain perception. However, so far, the spatiotemporal characteristics of neuronal activities associated with peripheral persistent nociception have rarely been studied. In the present report, we used c-Fos as a neuronal marker to analyze spatial and temporal patterns of pain-related neuronal activities within the S1 area of rats subjecting to subcutaneous (s.c.) injection of bee venom (BV) solution, a well-established animal model of persistent pain. In naïve and saline-treated rats, c-Fos-labeled neurons were diffusely and sparsely distributed in the hindlimb region of S1 area. Following s.c. BV injection, c-Fos-labeled neurons became densely increased in superficial layers (II–III) and less increased in deep layers (IV–VI). The mean number of c-Fos positive neurons in the layers II–III began to increase at 1 h and reached a peak at 2 h after BV treatment that was followed by a gradual decrease afterward. The time course of c-Fos expression in the layers IV–VI was in parallel with that of the superficial layers, but with a much lower density and magnitude. The present results demonstrated that BV-induced peripheral persistent nociception could evoke increased neuronal activities in the S1 area with predominant localization in layers II–III.     

Decreased Fos protein expression in rat caudal vestibular nucleus is associated with motion sickness habituation

We investigated the temporal change of Fos protein expression in the caudal vestibular nucleus of rats exposed to daily 2-h Ferris-wheel like (FWL) rotation. Repeated rotation (2 h daily for 14 consecutive days) caused an initial increase in defecation, followed by a gradual decline back to the baseline level after 8 rotation sessions. Unlike defecation, the Kaolin consumption of rats showed a bitonic function during the daily rotation sessions (2 h daily for 33 consecutive days) and finally recovered to the baseline after about 31 sessions. Immunohistochemistry study revealed increased Fos immunolabeled (Fos-LI) neurons in the medial vestibular nucleus and spinal vestibular nucleus during the initial 7 rotation sessions, and it decreased to the baseline level after 10 rotation sessions. There was a strong linear relationship between the amount of Fos-LI neurons and rat defecation level throughout the whole rotation sessions. These results suggest that the change of neuronal plasticity in the caudal vestibular nucleus might contribute to attenuation of gastrointestinal symptoms during motion sickness habituation process.     

Fine structural survey of Gudden's tegmental nuclei in the rat: cytology and axosomatic synapses

Summary The fine structure of neuronal somata and axosomatic synapses in each subnucleus of Gudden's tegmental nuclei was studied by use of electron microscopy. The pars principalis of the ventral tegmental nucleus of Gudden (TVP) is composed of oblong or triangular, medium sized neurons (11.8x22.6 m, 211.4 m²) containing many mitochondria, lysosomes, Golgi apparatus, and rough endoplasmic reticulum composing Nissl bodies. The light oval nucleus with a prominent nucleolus is centrally situated, and indentations of its nuclear envelope are recognized in all neurons. The neuron in the pars ventralis of the dorsal tegmental nucleus of Gudden (TDV) is similar to that in the TVP, but its average size is significantly smaller (10.0x18.8 m, 151.4 m²), and its organelles are also less well developed. The pars dorsalis of the dorsal tegmental nucleus of Gudden (TDD) is composed of spindle shaped, small neurons (6.9x16.2 m, 85.1 m²) characterized by their irregular shaped nucleus with its invaginated envelope. These neurons have a thin rim of cytoplasm, poorly developed organelles and no Nissl bodies. The average number of axosomatic terminals in a sectional plane is 9.9 in the TVP, 9.6 in the TDV and 2.6 in the TDD, and the bouton covering ratio is 24.3% in the TVP, 26.5% in the TDV and 7.4% in the TDD. The respective percentages of round, flat and pleomorphic type axosomatic terminals were estimated, and the flat type terminals were found to be dominant in the TVP, the pleomorphic type terminals in the TDV, and the round type terminals in the TDD.     

Neuromodulatory role of acetylcholine in visually-induced cortical activation: behavioral and neuroanatomical correlates

Acetylcholine is released in the primary visual cortex during visual stimulation and may have a neuromodulatory role in visual processing. The present study uses both behavioral and functional neuroanatomy investigations to examine this role in the rat. In the first set of experiments the cholinergic system was lesioned with 192 immunoglobulin G (IgG) saporin and the visual acuity and performance in a visual water maze task were assessed. The cholinergic lesion did not affect the visual acuity measured pre- and post-lesion but it did reduce the efficiency to learn a novel orientation discrimination task measured post-lesion. In order to better understand the involvement of the cholinergic system in the neuronal activity in the visual cortex c-Fos expression induced by patterned visual stimulation was further investigated. Results obtained following lesion of the cholinergic fibers (192 IgG-saporin or quisqualic acid), muscarinic inhibition (scopolamine), or NMDA receptor inhibition (CPP) were compared with control conditions. Double and triple immunolabeling was used in order to determine the neurochemical nature of the activated cortical cells. The results demonstrated that patterned stimulation elicited a significant increase in c-Fos immunolabeled neurons in layer IV of the contralateral primary visual cortex to the stimulated eye which was completely abolished by cholinergic fibers lesion as well as scopolamine administration. This effect was independent of NMDA receptor transmission. The c-Fos activation was predominantly observed in the glutamatergic spiny stellate cells and less frequently in GABAergic interneurons. Altogether, these results demonstrate a strong involvement of the basal forebrain cholinergic system in the modulation of post-synaptic visual processing, which could be related to cognitive enhancement or attention during visual learning.