Specific Regions Of Rat Brain Research Articles

Neurokinin-1 receptor antagonist rolapitant suppresses anxiety and alcohol intake produced by repeated withdrawal episodes.

Neurokinin-1 receptor (NK1r) antagonists have been shown to suppress operant self-administration of alcohol, voluntary alcohol consumption and stress-induced reinstatement of alcohol-seeking behaviour. Considering the long half-life and anxiolytic-like properties of NK1r antagonist rolapitant, we expected that it may be an effective option for reducing anxiety and alcohol motivation during early withdrawal. Voluntary alcohol intake (two-bottles paradigm) was recorded in male Wistar rats during the three periods: 24 days (basal level), 6-day period when rats received 5 mg·kg-1 rolapitant or vehicle and 12-h period after repeated withdrawal episodes (alcohol cessation for 36 h). We found that upon intraperitoneal (i.p.) administration, rolapitant rapidly penetrated into specific rat brain regions - amygdala, hypothalamus and neocortex - implicated in the control of anxiety and reward. Rolapitant did not affect basal voluntary alcohol intake, but significantly suppressed anxiety-like behaviour and alcohol consumption following withdrawal episodes. Our findings suggest that rolapitant should be further investigated as a novel treatment option for relapse prevention in alcohol-dependent patients.

Hypothermia selectively protects the anterior forebrain mesocircuit during global cerebral ischemia.

Hypothermia is an important protective strategy against global cerebral ischemia following cardiac arrest. However, the mechanisms of hypothermia underlying the changes in different regions and connections of the brain have not been fully elucidated. This study aims to identify the metabolic nodes and connection integrity of specific brain regions in rats with global cerebral ischemia that are most affected by hypothermia treatment. 18F-fluorodeoxyglucose positron emission tomography was used to quantitatively determine glucose metabolism in different brain regions in a rat model of global cerebral ischemia established at 31-33°C. Diffusion tensor imaging was also used to reconstruct and explore the brain connections involved. The results showed that, compared with the model rats established at 37-37.5°C, the rat models of global cerebral ischemia established at 31-33°C had smaller hypometabolic regions in the thalamus and primary sensory areas and sustained no obvious thalamic injury. Hypothermia selectively preserved the integrity of the anterior forebrain mesocircuit, exhibiting protective effects on the brain during the global cerebral ischemia. The study was approved by the Institutional Animal Care and Use Committee at Capital Medical University (approval No. XW-AD318-97-019) on December 15, 2019.

Midbrain and Lateral Nucleus Accumbens Dopamine Depletion Affects Free-choice High-fat high-sugar Diet Preference in Male Rats

Dopamine influences food intake behavior. Reciprocally, food intake, especially of palatable dietary items, can modulate dopamine-related brain circuitries. Among these reciprocal impacts, it has been observed that an increased intake of dietary fat results in blunted dopamine signaling and, to compensate this lowered dopamine function, caloric intake may subsequently increase. To determine how dopamine regulates food preference we performed 6-hydroxydopamine (6-OHDA) lesions, depleting dopamine in specific brain regions in male Sprague Dawley rats. Food preference was assessed by providing the rats with free choice access to control diet, fat, 20% sucrose and tap water. Rats with midbrain lesions targeting the substantia nigra (which is also a model of Parkinson’s disease) consumed fewer calories, as reflected by a decrease in control diet intake, but they surprisingly displayed an increase in fat intake, without change in the sucrose solution intake compared to sham animals. To determine which of the midbrain dopamine projections may contribute to this effect, we next compared the impact of 6-OHDA lesions of terminal fields, targeting the dorsal striatum, the lateral nucleus accumbens and the medial nucleus accumbens. We found that 6-OHDA lesion of the lateral nucleus accumbens, but not of the dorsal striatum or the medial nucleus accumbens, led to increased fat intake. These findings indicate a role for lateral nucleus accumbens dopamine in regulating food preference, in particular the intake of fat.

Methyl jasmonate ameliorates rotenone-induced motor deficits in rats through its neuroprotective activity and increased expression of tyrosine hydroxylase immunopositive cells.

Decreased tyrosine hydroxylase (TH) activity, due to degeneration of dopaminergic neurons contributes to the low dopamine content and the motor deficits that characterized Parkinson's disease (PD). This study examines the effect of methyl jasmonate (MJ), a neuroprotective bioactive compound isolated from jasminum grandiflorum, on motor functions, immunopositive cells of TH, dendritic neurons and dopamine contents in rotenone (Rot)-treated rats. Rats pretreated daily with MJ (100mg/kg, i.p) for 21days also received Rot (2.5mg/kg, i.p.) 30min after each pretreatment for every 48h for 21days. Motor functions were assessed on day 22. The specific brain regions of the rats were processed for determination of dopamine contents, immunopositive cells of TH, neuronal cell morphology and dendritic aborizations. Rot impaired locomotion and rearing behavior, and decreased dopamine content in the striatum, prefrontal cortex and midbrain. It further reduced the expression of TH in the substantia nigra and striatum relative to vehicle-control (p < 0.05). Histopathologic studies revealed that Rot-treated rats had degenerated neurons with pyknotic nuclei and loss of nigrostriatal neuronal cells. Rot also altered the nigrostriatal dendritic neuronal networks, decreased the dendritic length and spine density. However, pretreatment with MJ improved motor deficits, increased TH activity and dopamine contents in the specific brain regions of Rot-treated rats. MJ also attenuated the cyto-architectural distortions, loss of neuronal cells and dendritic aborizations of the striatum of Rot-treated rats. These findings suggest that MJ may reverse the motor deficits associated with PD by modifying the key pathological abnormalities involved in the disease progression.

Testosterone modulation of ethanol effects on the µ-opioid receptor kinetics in castrated rats.

The present investigation was conducted to evaluate the effects of testosterone on ethanol-induced alterations of µ-opioid receptor binding kinetics in specific brain regions of castrated rats. Male Sprague Dawley rats (100-124 g) adapted to a 12-h light/dark cycle were used. Animals were castrated under pentobarbital anesthesia. After a recovery period of 14 days, ethanol [3 g/kg as 22.5% solution in saline via intraperitoneal injection (i.p.)], testosterone [2.5 mg in 0.2 ml of olive oil via subcutaneous injection (s.c.) in the dorsal neck region] or the combination of ethanol and testosterone were administered to rats at 9:00 a.m. The control group was injected i.p. with 2 ml saline and s.c. with 0.2 ml olive oil for 7 days. Animals were sacrificed by decapitation at 2 h after the final injection. The brains were immediately removed, and the cortex, hippocampus, hypothalamus and midbrain were dissected. In an attempt to elucidate the mechanism involved in the hormonal modulation of the effects of ethanol and testosterone on the endogenous opioid system, the binding kinetics of the µ-opioid receptors were determined. The results obtained in the present study assisted in identifying the regulatory role of testosterone on ethanol-induced changes on µ-opioid receptor binding kinetics.

Interaction of Diet and Ozone Exposure on Oxidative Stress Parameters within Specific Brain Regions of Male Brown Norway Rats

Oxidative stress (OS) contributes to the neurological and cardio/pulmonary effects caused by adverse metabolic states and air pollutants such as ozone (O3). This study explores the interactive effects of O3 and diet (high-fructose (FRUC) or high–fat (FAT)) on OS in different rat brain regions. In acute exposure, there was a decrease in markers of reactive oxygen species (ROS) production in some brain regions by diet and not by O3. Total antioxidant substances (TAS) were increased in the cerebellum (CER) and frontal cortex (FC) and decreased in the striatum (STR) by both diets irrespective of O3 exposure. Protein carbonyls (PC) and total aconitase decreased in some brain regions irrespective of exposure. Following subacute exposure, an increase in markers of ROS was observed in both diet groups. TAS was increased in the FC (FAT only) and there was a clear O3 effect where TAS was increased in the FC and STR. Diet increased PC formation within the CER in the FAT group, while the hippocampus showed a decrease in PC after O3 exposure in controls. In general, these results indicate that diet/O3 did not have a global effect on brain OS parameters, but showed some brain region- and OS parameter-specific effects by diets.

Effects of haloperidol and clozapine on synapse-related gene expression in specific brain regions of male rats.

We investigated the effects of clozapine and haloperidol, drugs that are widely used in the treatment of schizophrenia, on gene expression in six cortical and subcortical brain regions of adult rats. Drug treatments started at postnatal day 85 and continued over a 12-week period. Ten animals received haloperidol (1mg/kg bodyweight) and ten received clozapine (20mg/kg bodyweight) orally each day. Ten control rats received no drugs. The ten genes selected for this study did not belong to the dopaminergic or serotoninergic systems, which are typically targeted by the two substances, but coded for proteins of the cytoskeleton and proteins belonging to the synaptic transmitter release machinery. Quantitative real-time PCR was performed in the prelimbic cortex, cingulate gyrus (CG1) and caudate putamen and in the hippocampal cornu ammonis 1 (CA1), cornu ammonis 3 (CA3) and dentate gyrus. Results show distinct patterns of gene expression under the influence of the two drugs, but also distinct gene regulations dependent on the brain regions. Haloperidol-medicated animals showed statistically significant downregulation of SNAP-25 in CA3 (p = 0.0134) and upregulation of STX1A in CA1 (p = 0.0133) compared to controls. Clozapine-treated animals showed significant downregulation of SNAP-25 in CG1 (p = 0.0013). Our results clearly reveal that the drugs' effects are different between brain regions. These effects are possibly indirectly mediated through feedback mechanisms by proteins targeted by the drugs, but direct effects of haloperidol or clozapine on mechanisms of gene expression cannot be excluded.

Water diffusion closely reveals neural activity status in rat brain loci affected by anesthesia.

Diffusion functional MRI (DfMRI) reveals neuronal activation even when neurovascular coupling is abolished, contrary to blood oxygenation level—dependent (BOLD) functional MRI (fMRI). Here, we show that the water apparent diffusion coefficient (ADC) derived from DfMRI increased in specific rat brain regions under anesthetic conditions, reflecting the decreased neuronal activity observed with local field potentials (LFPs), especially in regions involved in wakefulness. In contrast, BOLD signals showed nonspecific changes, reflecting systemic effects of the anesthesia on overall brain hemodynamics status. Electrical stimulation of the central medial thalamus nucleus (CM) exhibiting this anesthesia-induced ADC increase led the animals to transiently wake up. Infusion in the CM of furosemide, a specific neuronal swelling blocker, led the ADC to increase further locally, although LFP activity remained unchanged, and increased the current threshold awakening the animals under CM electrical stimulation. Oppositely, induction of cell swelling in the CM through infusion of a hypotonic solution (−80 milliosmole [mOsm] artificial cerebrospinal fluid [aCSF]) led to a local ADC decrease and a lower current threshold to wake up the animals. Strikingly, the local ADC changes produced by blocking or enhancing cell swelling in the CM were also mirrored remotely in areas functionally connected to the CM, such as the cingulate and somatosensory cortex. Together, those results strongly suggest that neuronal swelling is a significant mechanism underlying DfMRI.

Abstract 60: Inter-alpha Inhibitor Proteins Reduce the Quantity of Microglia in the Hippocampus After Hypoxic-ischemic Brain Injury in the Neonate

Background: Inter-alpha inhibitor proteins (IAIPs) are immunomodulatory proteins that act as anti-inflammatory agents in hypoxic-ischemic (HI) injury. We have recently shown that administering IAIP after HI improves histopathological brain injury, and behavioral outcomes in neonatal rats. Microglia are glial cells that act as macrophages in the brain and are important constituents in the neuroinflammatory response. Objective: To determine the effect of IAIP treatment on microglial expression in specific brain regions of neonatal rats after HI brain related injury. Methods: The Vannucci model was used to induce neonatal HI brain injury. Postnatal day 7 rats were assigned to a non-ischemic sham-control group (Sham, n=11), a right carotid ligation and hypoxia exposed (8% oxygen for 90 min) placebo-treated group (IschPL, n=12), or a right carotid ligation and hypoxia IAIP-treated group (Isch-IAIP, n=12). The sex of the rats was recorded. IAIP (30 mg/kg) or PL was given intraperitoneally at 0, 24 and 48 h after HI. 72 h after HI, brains were collected, sectioned, and prepared for slides. We performed immunohistochemistry by staining with Iba-1 (selective for microglia) and DAPI. Stereological analyses were then performed with the StereoInvestigator 10.0 Fractionator probe without knowledge of group assignment to quantify microglia present in the whole hemisphere, cortex, corpus callosum, and hippocampus. Results: The number of Iba-1 positive microglial cells per area of tissue was lower in Sham than in the Isch-PL animals in the cortex, hippocampus, and hemisphere of female and in the hippocampus and corpus callosum of male rats (P &lt;0.05). IAIP treatment appears to reduce the number of Iba-1 positive cells across all brain regions compared with the PL treated HI in the male but not female neonatal rats. Post hoc analysis showed that IAIP treatment significantly reduced the number of positive Iba-1 cells in the hippocampus of the male rats (P&lt;0.01).

Inhibiting HIF-1α Decreases Expression of TNF-α and Caspase-3 in Specific Brain Regions Exposed Kainic Acid-Induced Status Epilepticus

Background/Aims: A recent study demonstrates that pro-inflammatory cytokines (PICs, i.e., IL-1β, IL-6 and TNF-α) in specific brain regions of rats play a role in regulating kainic acid (KA)-induced status epilepticus (SE) via a GABAergic mechanism. The purposes of this report were to examine contributions of hypoxia inducible factor subtype 1α (HIF-1α) to expression of PICs in these specific brain regions in epileptic rats. Particularly, we investigated the parietal cortex, hippocampus and amygdala. In addition, we further examined expression of Caspase-3 indicating cell apoptosis in those brain regions of epileptic rats after infusing 2-methoxyestradiol (2-MET, inhibitor of HIF-1α) and etanercept (TNF-α receptor antagonist). Methods: ELISA was used to determine the levels of HIF-1α and PICs and western blot analysis was used to examine Caspase-3 expression. Results: Our data show that HIF-1α was significantly increased in the parietal cortex, hippocampus and amygdala 1, 3 and 7 days after induction of SE (P<0.05 vs. control rats). Our results also show that inhibiting HIF-1α by central infusion of 2-MET significantly decreased the amplified TNF-α expression in these brain regions evoked by SE (P<0.05 vs. vehicle control), but did not modify IL-1β and IL-6. Our results demonstrate that 2-MET and etanercept attenuated an increase in Caspase-3 evoked by SE. Conclusion: Overall, we suggest that HIF-1α activated by SE is likely to contribute to epileptic activity via a TNF-α pathway, which has pharmacological implications to target specific HIF-1α and TNF-α pathways for neuronal dysfunction and vulnerability related to epilepsy.

The proteins interacting with C-terminal of μ receptor are identified by bacterial two-hybrid system from brain cDNA library in morphine-dependent rats.

Opioid addiction is associated with long-term adaptive changes in the brain that involve protein expression. The carboxyl-terminal of the μ opioid receptor (MOR-C) is important for receptor signal transduction under opioid treatment. However, the proteins that interact with MOR-C after chronic morphine exposure remain unknown. The brain cDNA library of chronic morphine treatment rats was screened using rat MOR-C to investigate the regulator of opioids dependence in the present study. The brain cDNA library from chronic morphine-dependent rats was constructed using the SMART (Switching Mechanism At 5' end of RNA Transcript) technique. Bacterial two-hybrid system was used to screening the rat MOR-C interacting proteins from the cDNA library. RT-qPCR and immunoblotting were used to determine the variation of MOR-C interacting proteins in rat brain after chronic morphine treatment. Column overlay assays, immunocytochemistry and coimmunoprecipitation were used to demonstrate the interaction of MOR-C and p75NTR-associated cell death executor (NADE). 21 positive proteins, including 19 known proteins were screened to interact with rat MOR-C. Expression of several of these proteins was altered in specific rat brain regions after chronic morphine treatment. Among these proteins, NADE was confirmed to interact with rat MOR-C by in vitro protein-protein binding and coimmunoprecipitation in Chinese hamster ovary (CHO) cells and rat brain with or without chronic morphine treatment. Understanding the rat MOR-C interacting proteins and the proteins variation under chronic morphine treatment may be critical for determining the pathophysiological basis of opioid tolerance and addiction.

Methamphetamine induces DNA damage in specific regions of the female rat brain.

Methamphetamine (METH) is a highly addictive psychostimulant that has been shown to produce neurotoxicity. Methamphetamine increases the release of dopamine by reversing the direction of monoamine transporter proteins, leading to the formation of reactive oxygen species in the brain. In this study, we examined the effect of METH on DNA damage in vivo using the single cell gel electrophoresis assay (comet assay) under two different conditions. Rats treated with multiple doses of METH (10 mg/kg × 4) showed significant levels of DNA damage in the nucleus accumbens and striatum, both dopamine-rich areas. In contrast, a single dose of METH did not lead to significant levels of DNA damage in any of the dopamine-rich brain regions that were tested. Overall, the results of our study demonstrate that METH produces greater oxidative DNA damage in brain areas that receive greater dopamine innervation.

Effect of Ginkgo biloba Extract on Lead-Induced Oxidative Stress in Different Regions of Rat Brain.

Ginkgo biloba extract (GbE) is a well known natural antioxidant. In the present investigation, its ameliorative effects were tested against lead-induced oxidative stress in rat brain. Four groups of male Wistar rats (100 to 120 g) were used, consisting of eight rats per group. Rats in the control group received 500 ppm of sodium acetate through drinking water, and rats in the other three groups received 500 ppm of lead acetate through drinking water for 4 weeks. Rats in the third and fourth groups were administered (oral) 50 and 100 mg/kg of GbE, respectively, along with lead acetate. The rats were sacrificed after treatment and brains were isolated. Each brain was dissected on ice, and different regions, namely the cerebellum, hippocampus, frontal cortex, and brainstem, were separated. The results revealed a significant (P < .001) increase in reactive oxygen species, catalase, superoxide dismutase, lipid peroxidation products, and total protein carbonyl content, relative to their controls, in all four regions of the brain exposed to lead. These results indicate oxidative stress. Partial restoration was observed for all the parameters just mentioned in different brain regions on treatment with 50 mg/kg GbE. This amelioration was higher with 100 mg/kg GbE, showing dose-dependency. Overall the data suggest that GbE protects against lead-induced oxidative stress in specific regions of rat brain.

Nefiracetam Attenuates Pro-Inflammatory Cytokines and GABA Transporter in Specific Brain Regions of Rats with Post-Ischemic Seizures

Background/Aims: Prior studies demonstrated that pro-inflammatory cytokines (PICs) including IL-1β, IL-6 and TNF-α contribute to regulation of epilepsy-associated pathophysiological processes in the specific brain regions, namely the parietal cortex, hippocampus and amygdala. Moreover, GABA transporter type 1 and 3 (GAT-1 and GAT-3) modulating extracellular GABA levels are engaged in the role played by PICs in epileptogenesis. Note that brain ischemic injury also elevates cerebral PICs. Thus, in this report we examined the effects of nefiracetam (NEF), a pyrrolidone derivative, on the levels of IL-1β, IL-6 and TNF-α, and expression of GAT-1 and GAT-3 in the parietal cortex, hippocampus and amygdala using a rat model of post-ischemic nonconvulsive seizure (NCS). Methods: NCS was evoked by the middle cerebral artery occlusion (MCAO). ELISA and Western Blot analysis were employed to determine the levels of PICs and GAT-1/GAT-3, respectively. Results: MCAO significantly increased IL-1β, IL-6 and TNF-α in the parietal cortex, hippocampus and amygdala as compared with sham control animals (P<0.05 vs. control rats). Also, in these specific brain regions expression of GAT-1 and GAT-3 was amplified; and the levels of GABA were decreased in rats following MCAO (P<0.05 vs. control rats). Systemic administration of NEF significantly attenuated the elevated PICs, amplified GAT-1 and GAT-3 as well as impaired GABA. NEF also attenuated the number of NCS events following MCAO. Conclusion: our data demonstrate that NEF improves post-ischemia evoked-NCS by altering PICs, GABA transporters thereby alleviating GABA in the parietal cortex, hippocampus and amygdala. This support a role for PICs and GABA in engagement of the adaptive responses associated with epileptic activity, but also suggests that NEF has anti-epileptic effects via PICs-GABA mechanisms, having pharmacological implications to target the specific PICs for neuronal dysfunction and vulnerability related to post-ischemic seizures and cognitive impairment.

Effect of Plumbago zeylanica administration on brain neurotransmitter level in Wistar albino rats

According to WHO about 80% of the world’s population relies on traditional medicine for their primary health care.Plumbago zeylanica L. is a medicinal plant, belong to the family of Plumbaginaceae and the root of P. zeylanica contains several bioactive constituent like L-dopa, Plumbagin (naphthoquinone), droseron, chitranone, triterpenoid, anthraquinone. This study is designed to evaluate the effect of P. zeylanica and naphthoquinone on the level of various amine neurotransmitters namely epinephrine, norepinephrine, serotonin, 5-hydroxyindole 3-acetic acid (5-HIAA), and dopamine on the discrete regions of the brain tissues. Wistar male albino rats were treated separately with ethanoloic extract of P.zeylannica (root) and the commercially purchased phytochemical naphthoquinone at the dose of 2mg/kg b.wt with different experimental groups. The brain tissue homogenates (cerebral cortex, cerebellum, hypothalamus, pons-medulla, midbrain, and corpus striatum) were analyzed to quantify the aforementioned neurotransmitters by high performance liquid chromatography (HPLC). The results showed that, administration of P. zeylanicaand NQ does not alter the many of the studied neurotransmitter at significant level; however, there is a change in the neurotransmitter profile in few specific regions of Wistar rat brain and striatum was found to be affected more.

Endogenous concentrations of biologically relevant metals in rat brain and cochlea determined by inductively coupled plasma mass spectrometry.

Manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) are essential nutrients which aid in the proper functioning of cells, but high concentrations of these metals can be toxic to various organs. Little is known about the endogenous concentrations of these metals in the cochlea, the auditory portion of the inner ear which is extremely small and difficult to access. To fill this gap, a trace quantitative digestion and inductively coupled plasma mass spectrometry method was developed to determine the concentrations of these metals in the stria vascularis, organ of Corti, and spiral ganglion, three critically important parts of the cochlea (≤ 1.5 mg); these values were compared to those in specific brain regions (≤ 20 mg) of rats. Rats were sacrificed and the cochlea and brain regions were carefully isolated, digested, and analyzed to determine baseline concentrations of Mn, Fe, Cu, and Zn. In the cochlea, Mn, Fe, Cu, and Zn concentrations ranged from 3.2-6, 73-300, non-detect, and 13-200 µg/g respectively. In the brain, Mn, Fe, Cu, and Zn concentrations ranged from 1.3-2.72, 21-120, 5.0-10.6, and 33-47 µg/g respectively. Significant differences (p < 0.05) were observed between the tissue types within the cochlea, and between the cochlea and brain. This validated method provides the first quantitative assessment of these metals in the three key subdivisions of the cochlea compared to the levels in the brain; Mn, Fe, and Zn levels were considerably higher in the cochlea than brain.

Influence of Post-Traumatic Stress Disorder on Neuroinflammation and Cell Proliferation in a Rat Model of Traumatic Brain Injury

Long-term consequences of traumatic brain injury (TBI) are closely associated with the development of severe psychiatric disorders, such as post-traumatic stress disorder (PTSD), yet preclinical studies on pathological changes after combined TBI with PTSD are lacking. In the present in vivo study, we assessed chronic neuroinflammation, neuronal cell loss, cell proliferation and neuronal differentiation in specific brain regions of adult Sprague-Dawley male rats following controlled cortical impact model of moderate TBI with or without exposure to PTSD. Eight weeks post-TBI, stereology-based histological analyses revealed no significant differences between sham and PTSD alone treatment across all brain regions examined, whereas significant exacerbation of OX6-positive activated microglial cells in the striatum, thalamus, and cerebral peduncle, but not cerebellum, in animals that received TBI alone and combined TBI-PTSD compared with PTSD alone and sham treatment. Additional immunohistochemical results revealed a significant loss of CA3 pyramidal neurons in the hippocampus of TBI alone and TBI-PTSD compared to PTSD alone and sham treatment. Further examination of neurogenic niches revealed a significant downregulation of Ki67-positive proliferating cells, but not DCX-positive neuronally migrating cells in the neurogenic subgranular zone and subventricular zone for both TBI alone and TBI-PTSD compared to PTSD alone and sham treatment. Comparisons of levels of neuroinflammation and neurogenesis between TBI alone and TBI+PTSD revealed that PTSD did not exacerbate the neuropathological hallmarks of TBI. These results indicate a progressive deterioration of the TBI brain, which, under the conditions of the present approach, was not intensified by PTSD, at least within our time window and within the examined areas of the brain. Although the PTSD manipulation employed here did not exacerbate the pathological effects of TBI, the observed long-term inflammation and suppressed cell proliferation may evolve into more severe neurodegenerative diseases and psychiatric disorders currently being recognized in traumatized TBI patients.

Methacarn as a whole brain fixative for gene and protein expression analyses of specific brain regions in rats

For molecular analysis in anatomically-specific brain regions for rodent studies, it is necessary to establish a fast and accurate procedure for tissue sampling to achieve high integrity and expression fidelity of extracted molecules. The present study was performed to examine suitability of whole brain fixation with methacarn and subsequent tissue sampling using punch-biopsy devices for gene expression analysis in rats. After fixation, each specific region, i.e., hippocampal dentate gyrus, corpus callosum, cingulate cortex or cerebellar vermis was collected, and the integrity and variability of expression data of extracted total RNAs and polypeptides were examined. Methacarn fixation, acetone fixation, and unfixed tissues were compared. Methacarn fixation resulted in high integrity of total RNAs sufficient for conducting global expression analysis and superior in terms of uniformity in the integrity among brain regions to that of acetone fixation. Extracted polypeptide after methacarn fixation revealed similar integrity to that without fixation or with acetone fixation. Methacarn fixation resulted in lower mRNA expression variability between samples than acetone fixation in microarray analysis. The fidelity of polypeptide expression was mostly equivalent between methacarn and acetone fixation in 2-dimensional differential in-gel electrophoresis, although the expression levels of a small number of polypeptides from acetone-fixed tissues were affected. These results suggest that whole brain fixation with methacarn retains advantages for global analyses of mRNAs and polypeptides in rodent studies.

Biological sex influences learning strategy preference and muscarinic receptor binding in specific brain regions of prepubertal rats

According to the theory of multiple memory systems, specific brain regions interact to determine how the locations of goals are learned when rodents navigate a spatial environment. A number of factors influence the type of strategy used by rodents to remember the location of a given goal in space, including the biological sex of the learner. We recently found that prior to puberty male rats preferred a striatum-dependent stimulus-response strategy over a hippocampus-dependent place strategy when solving a dual-solution task, while age-matched females showed no strategy preference. Because the cholinergic system has been implicated in learning strategy and is known to be sexually dimorphic prior to puberty, we explored the relationship between learning strategy and muscarinic receptor binding in specific brain regions of prepubertal males and female rats. We confirmed our previous finding that at 28 days of age a significantly higher proportion of prepubertal males preferred a stimulus-response learning strategy than a place strategy to solve a dual-solution visible platform water maze task. Equal proportions of prepubertal females preferred stimulus-response or place strategies. Profiles of muscarinic receptor binding as assessed by autoradiography varied according to strategy preference. Regardless of biological sex, prepubertal rats that preferred stimulus-response strategy exhibited lower ratios of muscarinic receptor binding in the hippocampus relative to the dorsolateral striatum compared to rats that preferred place strategy. Importantly, much of the variance in this ratio was related to differences in the ventral hippocampus to a greater extent than the dorsal hippocampus. The ratios of muscarinic receptors in the hippocampus relative to the basolateral amygdala also were lower in rats that preferred stimulus-response strategy over place strategy. Results confirm that learning strategy preference varies with biological sex in prepubertal rats with males biased toward a stimulus-response strategy, and that stimulus-response strategy is associated with lower ratios of muscarinic binding in the hippocampus relative to either the striatum or amygdala.

Iron-Responsive Olfactory Uptake of Manganese Improves Motor Function Deficits Associated with Iron Deficiency

Iron-responsive manganese uptake is increased in iron-deficient rats, suggesting that toxicity related to manganese exposure could be modified by iron status. To explore possible interactions, the distribution of intranasally-instilled manganese in control and iron-deficient rat brain was characterized by quantitative image analysis using T1-weighted magnetic resonance imaging (MRI). Manganese accumulation in the brain of iron-deficient rats was doubled after intranasal administration of MnCl2 for 1- or 3-week. Enhanced manganese level was observed in specific brain regions of iron-deficient rats, including the striatum, hippocampus, and prefrontal cortex. Iron-deficient rats spent reduced time on a standard accelerating rotarod bar before falling and with lower peak speed compared to controls; unexpectedly, these measures of motor function significantly improved in iron-deficient rats intranasally-instilled with MnCl2. Although tissue dopamine concentrations were similar in the striatum, dopamine transporter (DAT) and dopamine receptor D1 (D1R) levels were reduced and dopamine receptor D2 (D2R) levels were increased in manganese-instilled rats, suggesting that manganese-induced changes in post-synaptic dopaminergic signaling contribute to the compensatory effect. Enhanced olfactory manganese uptake during iron deficiency appears to be a programmed “rescue response” with beneficial influence on motor impairment due to low iron status.