Region Of Rats Research Articles

Neuroprotective and anti-stress effect of A68930 in acute and chronic unpredictable stress model in rats

The neurorescuing effect of A68930 (a potent selective D1 agonist) and its role on the regulation of hypothalamus–pituitary–adrenal (HPA)-axis have been investigated. Acute (AS) and chronic unpredictable (CUS) stress models were used to evaluate the effect of A68930 on HPA-axis regulation in relation to the change in the fiber density and number of immunoreactive (ir) neurons of tyrosine hydroxylase (TH) and glucocorticoid receptor (GR) in the dopamine (DA) and GR rich brain regions in rats. CUS caused a significant decrease in the number of TH ir neurons in the striatum, medial forebrain bundle, ventral tegmental area and substansia nigra and GR in the cortex, striatum and hippocampus as compared to the non-stress controls (NS). Administration of A68930 (0.25mg/kg i.p.) significantly normalized these CUS-induced alterations. We also examined the role of A68930 on stress-induced brain oxidative status. AS enhanced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the cortex and striatum, while CUS reduced the activities of SOD and catalase (CAT) in the cortex, striatum and hippocampus, when compared with NS. Increased GSH-Px activity, with reduced glutathione and increased lipid peroxidation was observed in both AS and CUS in selected brain regions as compared to NS. Administration of A68930 normalized the antioxidant enzyme activities, replenished GSH and decreased the extent of lipid peroxidation. In conclusion, present findings suggest that the stress-induced immunoreactivity of TH and GR in distinct brain regions are modulated by A68930 leading to the normalization of HPA-axis response. Ours results show the therapeutic importance of DA D1 agonist in stress-induced dopaminergic-related neurological disorders. A68930 also influenced the brain antioxidant machinery probably through the restoration of stress-induced changes in the dopaminergic system and its crosstalk with GR.

Immunohistochemical localization and characterization of distinct angiotensin II AT1 and AT2 receptor isoforms in the adrenal glands of the Sprague-Dawley rat and the desert rodent Meriones crassus

Employing specific polyclonal anti-AT1 and anti-AT2 antibodies, AT1 and AT2 receptor expression was immunohistochemically demonstrable within adrenal tissues in Sprague-Dawley rats and the desert rodent Meriones crassus. Among adrenal cortical zones in rats, AT1 receptor labeling was evident in zona glomerulosa and zona reticularis. In contrast, AT1 receptor labeling was confined to the zona glomerulosa and the deep zona fasiculata in Meriones crassus. AT1 receptor labeling was, however, equally observed among ganglion and chromaffin cells constituting the adrenal medulla of both animal models. AT2 receptor labeling was faint in all adrenal regions in rats. However, intensity was high in the deep zona fasiculata, and medullary chromaffin and ganglion cells in Meriones crassus. Two-dimensional Western blotting, in the presence or absence of endoglycosidase-F, revealed that structurally distinct spectra of AT1 and AT2 receptor isoforms are expressed in the adrenal tissues of each animal model. These spectra were constituted by molecular isoforms with distinct patterns of charge microheterogeneity unique to each receptor type in each animal model. In both species, heterogeneity of AT1 and AT2 receptor isoforms may be attributed in part to differential post-translational glycosylation mechanisms of the receptor polypeptide backbones, which may be critical in differentially fine-tuning adrenal functions in lab-reared and desert rodents. Key words: Angiotensin II receptors, adrenal gland, desert rodents, N –linked glycosylation, immunohistochemistry.

Requirement of α7 nicotinic acetylcholine receptors for amyloid beta protein‐induced depression of hippocampal long‐term potentiation in CA1 region of rats in vivo

The high density of senile plaques with amyloid beta protein (Aβ) and the loss of cholinergic neurons in the brain are the dominated pathological characteristics of Alzheimer's disease (AD). However, the active center of Aβ, especially the cholinergic mechanism underlying the Aβ neurotoxicity, is mostly unknown. This study examined the effects of different Aβ fragments on hippocampal long-term potentiation (LTP) and investigated its probable α7 nicotinic acetylcholine receptors (nAChRs) mechanism. The results show that: (1) intracerebroventicular injection of Aβ25-35 or Aβ31-35 significantly and similarly suppressed hippocampal LTP in CA1 region in rats; (2) choline, a selective α7 nAChR agonist, did not affect the LTP induction but enhanced LTP suppression induced by Aβ31-35; and (3) methyllycaconitine, a specific α7 nAChR antagonist, slightly suppressed hippocamal LTP but effectively prevented against Aβ31-35-induced LTP depression in the presence of Aβ31-35. These results indicate that: (1) the amino acid sequence 31-35 of the Aβ peptide might be a shorter active sequence in the full length molecule; (2) α7 nAChRs are required for the Aβ-induced suppression of hippocampal LTP. Thus, this study not only provides a new insight into the mechanism by which Aβ impairs synaptic plasticity but also strongly suggests that sequence 31-35 in Aβ molecule and α7 nAChRs in the brain might be potential therapeutic targets for the treatment of AD.

Expression of the mRNA of neurotrophins in brain regions of rats after spontaneous morphine withdrawal

The expression of specific genes is an important factor of neuroplastic changes during the formation of opiate dependence. Neurotrophic factors participate in structural-functional modifications in CNS regions after opiate intoxication. Here, we studied the levels of mRNAs of the brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and insulin-like growth factor 1 (IGF1) in the frontal cortex, striatum, hippocampus, and midbrain after spontaneous morphine withdrawal in dependent rats. To induce physical dependence, morphine was injected intraperitoneally twice a day with increasing doses of 10–100 mg/kg for 6 days. The expression of mRNAs of BDNF, NGF, and IGF1 in the brain areas was estimated 40 hours after spontaneous morphine withdrawal using the real-time PCR method. We found that spontaneous morphine withdrawal induced an elevation of BDNF and IGF1 mRNAs in the frontal cortex. In the hippocampus and the midbrain only BDNF mRNA increased. The content of NGF mRNA did not change in all regions studied. We believe that changes in the expression of BDNF and IGF1 are involved in the mechanisms of neuroplastic modification during the formation of opiate dependence.

Neurotransmitter systems of some brain regions of rats subjected to chronic morphine intoxication

The content of neurotransmitters and their metabolites was investigated in brain cortex hemispheres, thalamus and brainstem of rats subjected to chronic morphine intoxication (7–21 days). Morphine administration for 7–14 days was accompanied by changes of the catecholamine system functioning, which was the most pronounced in the thalamus and the brainstem. These changes included increased secretion of dopamine and noradrenaline, their decrease in the brain tissue, and an increased content of their metabolites. The changes in serotonin and GABA content were less pronounced and included a decrease of serotonin level and the increase of the GABA content in different periods of opiate administration.

Mild Prenatal Stress-Modulated Behavior and Neuronal Spine Density without Affecting Amphetamine Sensitization

The present study investigated the effect of prenatal stress (PS) on juvenile behavior and adult amphetamine (AMPH) sensitization, as well as the effect of the interaction between experience (i.e. PS) and drug (i.e. AMPH) on cortical thickness and neuronal morphology in corticolimbic regions in rats. Juvenile male and female rats, exposed to gestational stress, were tested in behavioral tasks that included open field locomotion, elevated plus maze, novel object recognition, and play fighting behavior. The development and persistence of drug-induced behavioral sensitization in adults were tested by chronic AMPH administration and challenge, respectively. Spine density in corticolimbic regions was examined for structural plasticity. The findings showed that PS produced anxiety-like behavior in males. Furthermore, PS in males resulted in female-like play and enhanced partial rotation defense, whereas in females PS increased the probability of evasion in response to an attack. AMPH administration resulted in gradual increase in behavioral sensitization that persisted at least for 2 weeks; however, PS did not influence AMPH-induced behavioral sensitization in either male or female rats. Moreover, PS increased the spine density in the nucleus accumbens (NAc) and decreased it in the medial prefrontal cortex (mPFC) without any alteration in the orbital frontal cortex (OFC). Similarly, AMPH administration increased spine density in the NAc and mPFC, whereas a decrease was observed in the OFC. However, PS prevented the drug-induced alterations in the spine density observed in controls. In sum, PS modulated juvenile behavior and altered brain morphology without influencing AMPH-induced behavioral sensitization substantially.

Effects of Localized Hydrophilic Mannitol and Hydrophobic Nelfinavir Administration Targeted to Olfactory Epithelium on Brain Distribution

Many nasally applied compounds gain access to the brain and the central nervous system (CNS) with varying degree. Direct nose-to-brain access is believed to be achieved through nervous connections which travel from the CNS across the cribriform plate into the olfactory region of the nasal cavity. However, current delivery strategies are not targeted to preferentially deposit drugs to the olfactory at cribriform. Therefore, we have developed a pressurized olfactory delivery (POD) device which consistently and non-invasively deposited a majority of drug to the olfactory region of the nasal cavity in rats. Using both a hydrophobic drug, mannitol (log P = -3.1), and a hydrophobic drug, nelfinavir (log P = 6.0), and POD device, we compared brain and blood levels after nasal deposition primarily on the olfactory region with POD or nose drops which deposited primarily on the respiratory region in rats. POD administration of mannitol in rats provided a 3.6-fold (p < 0.05) increase in cortex-to-blood ratio, compared to respiratory epithelium deposition with nose drop. Administration of nelfinavir provided a 13.6-fold (p < 0.05) advantage in cortex-to-blood ratio with POD administration, compared to nose drops. These results suggest that increasing the fraction of drug deposited on the olfactory region of the nasal cavity will result in increased direct nose-to-brain transport.

Maternal separation altered behavior and neuronal spine density without influencing amphetamine sensitization

We studied the long-term influence of maternal separation (MS) on periadolescent behavior, adult amphetamine (AMPH) sensitization, and structural plasticity in the corticolimbic regions in rats. Male and female pups, separated daily for 3 h from the dam during postnatal day 3–21, were tested for periadolescent exploratory, emotional, cognitive, and social behaviors. The development and persistence of drug-induced behavioral sensitization were tested by repeated AMPH administration and a challenge, respectively. The spine density was examined in the nucleus accumbens (NAc), the medial prefrontal cortex (mPFC), and the orbital frontal cortex (OFC) from Golgi-Cox stained neurons. The results showed that MS enhanced anxiety-like behavior in males. MS abolished the sex difference in playful attacks observed in controls with resultant feminization of male play behavior. Furthermore, the probability of complete rotation defense to face an attack was decreased in females. AMPH administration resulted in the development of behavioral sensitization that persisted at least for two weeks. Sensitization was not influenced by MS. MS increased the spine density in the NAc, the mPFC, and the OFC. Repeated AMPH administration increased the spine density in the NAc and the mPFC, and decreased it in the OFC. MS blocked the drug-induced alteration in these regions. In sum, MS during development influenced periadolescent behavior in males, and structurally reorganized cortical and subcortical brain regions without affecting AMPH-induced behavioral sensitization.

Mediators of the Plasma Extravasation Response to Silver Nitrate in the Rat Skin, Subplantar Region and Ankle Joint

Plasma extravasation responses to silver nitrate (AgNO3), histamine, 5-hydroxytryptamine (5-HT), bradykinin and prostaglandin E1 (PGE1) in the abdominal skin, hindpaw ankle joint and subplantar region of rats have been investigated using the Evans blue dye leakage technique. All substances tested produced plasma extravasation and combination of low doses (5 x 10(-10) mol) of either histamine or bradykinin with PGE1 (5 x 10(-10) mol) exhibited potentiation of responses of all regions. Responses to AgNO3 (1 x 10(-6) mol) were significantly reduced by the H1 receptor antagonist, mepyramine, only in the abdominal skin, but the H2 receptor antagonist metiamide reduced the responses at subplantar and ankle joint regions. Indomethacin significantly reduced the AgNO3 responses at the ankle joint only, but aprotinin reduced it at the other two regions. In rats pretreated with a combination of all antagonists the residual plasma extravasation response to AgNO3 was very small, indicating that the response could be almost totally accounted for by the combined actions of mast cell amines, kinins and prostanoids. The finding that prostanoids played a major role in the plasma extravasation response of the rat ankle joint to AgNO3 indicated that this model would be useful for the screening of non-steroidal anti-inflammatory drugs.

Opiate-receptor mediated changes in monoamine synthesis in rat brain.

Abstract The effects of morphine, β-endorphin, naloxone and naltrexone on the rate of tyrosine and tryptophan hydroxylation were investigated in vivo by measuring the accumulation of dopa and 5-hydroxytryptophan (5-HTP) in different brain regions of rats after inhibition of the aromatic L-amino acid decarboxylase. The cerebral concentrations of tyrosine and tryptophan were also measured. Morphine (3–30 mg kg−1) increased the accumulation of dopa dose-dependently (25–50%) in the dopamine-rich areas (limbic forebrain and corpus striatum). In the noradrenaline-predominant parts of the brain (containing hemispheres, diencephalon and lower brain stem) only the highest dose of morphine (30 mg kg−1) significantly increased dopa formation (47%). Similarly to morphine, intracerebroventricularly injected β-endorphin (5–10 βg per rat) increased the formation of dopa. This increase was doubled in limbic forebrain, corpus striatum and cerebral hemispheres. Doses of 10 to 20 μg of β-endorphin were needed to increase dopa accumulation in the diencephalon and the lower brain stem. Naloxone antagonized the β-endorphin-induced increases in dopa. But naloxone and naltrexone (10–100 mg kg−1) decreased the dopa formation in the dopamine-rich areas (about 20–25 %) but not in the noradrenaline-predominant areas. Morphine (30 mg kg−1) and β-endorphin (5 μg per rat) increased the accumulation of 5-HTP whereas naloxone and naltrexone (10 mg kg−1) tended to decrease its formation. Morphine and β-endorphine increased the concentrations of tyrosine and tryptophan, and naloxone decreased the cerebral tryptophan concentration. These results show that the effects of a narcotic agonist (morphine) and of pure narcotic antagonists (naloxone and naltrexone) on the synthesis of dopamine and 5-HT are opposite to each other. Furthermore, the effects of β-endorphine on brain monoamine synthesis are remarkably similar to those of morphine. Thus, it is probable that opiate receptors and their endogenous ligands are involved in the regulation of dopamine and 5-HT synthesis.

Localization of fenfluramine and reserpine in brain regions of rats with extensive degeneration of 5-hydroxytryptaminergic neurons.

Localization of fenfluramine and reserpine in brain regions of rats with extensive degeneration of 5-hydroxytryptaminergic neurons.

Ex vivo evaluation of the serotonin 1A receptor partial agonist [3H]CUMI‐101 in awake rats

[³H]CUMI-101 is a 5-HT(1A) partial agonist, which has been evaluated for use as a positron emission tracer in baboon and humans. We sought to evaluate the properties of [³H]CUMI-101 ex vivo in awake rats and determine if [³H]CUMI-101 can measure changes in synaptic levels of serotonin after different challenge paradigms. [³H]CUMI-101 shows good uptake and good specific binding ratio (SBR) in frontal cortex 5.18 and in hippocampus 3.18. Binding was inhibited in a one-binding-site fashion by WAY100635 and unlabeled CUMI-101. The ex vivo B(max) of [³H]CUMI-101 in frontal cortex (98.7 fmol/mg) and hippocampus (131 fmol/kg) agree with the ex vivo B(max) of [³H]MPPF in frontal cortex (147.1 fmol/mg) and hippocampus (72.1 fmol/mg) and with in vitro values reported with 8-OH-DPAT. Challenges with citalopram, a selective serotonin reuptake inhibitor, fenfluramine, a serotonin releaser, and 4-chloro-DL-phenylalanine, a serotonin synthesis inhibitor, did not show any effect on the standardized uptake values (SUVs) in any region. Citalopram did alter SBR, but this was due to changes in cerebellar SUVs. Our results indicate that [³H]CUMI-101 is a good radioligand for imaging 5-HT(1A) high-density regions in rats; however, the results from pharmacological challenges remain inconclusive.

Direct effect of nicotine on mesolimbic dopamine release in rat nucleus accumbens shell

Nicotine stimulates dopamine (DA) cell firing via a local action at somatodendritic sites in the ventral tegmental area (VTA), increasing DA release in the nucleus accumbens (NAcc). Additionally, nicotine may also modulate DA release via a direct effect in the NAcc. This study examined the contribution of the latter mechanism on NAcc DA release by applying nicotine systemically, as well as locally in the VTA and NAcc shell region in rats. Furthermore, the effect of i.v. nicotine on cell firing rate of dopaminergic neurons in the VTA was measured. Systemic administration of nicotine (0.32 mg/kg s.c.) increased extracellular DA levels in the NAcc to ∼1.5 fold of baseline, while DA levels in the VTA remained unaffected. A similar DA increase was observed after local NAcc infusion of nicotine (1 μM and 10 μM). However, 10–1000-fold higher nicotine concentrations were required in the VTA to produce a comparable 150% increase in extracellular DA levels in the ipsilateral NAcc. Additionally, electrophysiological experiments showed that the dopaminergic firing rate in the VTA showed a trend towards an increase after a nicotine dose of 0.1 mg/kg i.v. Taken together these data indicate that the effects of nicotine on DA release at the level of the NAcc might be more important for the rewarding effects than originally proposed.

Quantitative and Qualitative Analyses of Low-mineral-diet Ovariectomised Rat Femora Using Microscopic Computed Tomography

The aim of this study was to monitor changes in bone density and bone quality (microarchitecture) in the femoral epiphyseal region in rats with bone loss induced by oestrogen deficiency and accelerated by mineral deficiency. Forty-eight Wistar rats were divided into 3 groups (n = 16 per group): Group 1, sham-operated rats on a normal diet; Group 2, ovariectomised rats on a normal diet; and Group 3, ovariectomised rats on a mineral-deficient diet. Observations were conducted 4, 8, 16, and 24 weeks after the operation (sham or ovariectomy), while the rats were on their respective diets. Microscopic computed tomography of the femoral epiphyseal region was used to generate 3-dimensional bone density distribution maps, and to compute bone density values. Densities of cortical and cancellous bone in Groups 2 and 3 were significantly less than densities in Group 1, and densities in Group 3 were significantly less than densities in Group 2 at nearly every post-operative time interval.This study demonstrated that: a) ovariectomy in rats induces bone loss; b) a mineral-deficient diet accelerates bone loss that has been induced by oestrogen deficiency; and c) 3-dimensional bone density distribution maps may be useful in diagnosing osteoporosis and other diseases causing bone loss. Microscopic computed tomography is a powerful analytical tool for measuring spatial variations in bone density, and temporal changes in the patterns of 3-dimensional bone density distribution maps.

Human Dental Pulp Stem Cells associated to silk protein scaffold restore critical size bone defects in vivo

The aim of this study is to evaluate potential of fibroin scaffold combined with human dental pulp stem cells (hDPSC) to reconstruct large sized cranial bone defects in animal model. We performed two symmetric full-thickness cranial defects on each parietal region of rats and we replenished them with collagen, poly-D,L-lactic acid (PDLLA) and silk fibroin scaffolds with or without stem cells already seeded into and addressed towards osteogenic lineage in vitro. Animals were euthanized after 4 weeks postoperatively and cranial tissue samples were taken for histological analysis. The presence of human cells in the new bone was confirmed by confocal analysis with an antibody directed to a human mitochondrial protein. We observed a mature bone formation and the most relevant defects correction in constructs with fibroin. Our findings demonstrated the strong potential of bioengineered constructs of stem cells-fibroin scaffold for correcting large cranial defects in animal model and constitutes a promising model for reconstruction of human large cranial defects in craniofacial surgery.

The Effect of Training on Motoneuron Survival in Amyotrophic Lateral Sclerosis: Which Motoneuron Type is Saved?

The Effect of Training on Motoneuron Survival in Amyotrophic Lateral Sclerosis: Which Motoneuron Type is Saved?

Lamotrigine blocks apoptosis induced by repeated administration of high-dose methamphetamine in the medial prefrontal cortex of rats

Lamotrigine (LTG) is sometimes co-administered with antipsychotic drugs for the treatment of schizophrenia. Nevertheless, the pharmacological basis of LTG use for schizophrenia has not been reported. Our group recently proposed a new psychostimulant animal model that might reflect the progressive pathophysiology of schizophrenia. Results obtained using that model show that LTG blocks the initiation and expression of repeated high-dosage methamphetamine-induced prepulse inhibition deficit in rats (Nakato et al., 2010, Neurosci. Lett. [25]). Using the model, the effect of LTG (30mg/kg) on methamphetamine (METH, 2.5mg/kg)-induced increases in extracellular glutamate levels in the medial prefrontal cortex (mPFC) was examined in this study. Then the effect of repeated co-administration of LTG (30mg/kg) on repeated METH (2.5mg/kg)-induced apoptosis in this region of rats was investigated. Results show that LTG (30mg/kg) blocked the METH (2.5mg/kg)-induced glutamate increase in the mPFC. Repeated co-administration of LTG (30mg/kg) blocked the development of apoptosis induced by repeated administration of METH (2.5mg/kg) in the mPFC. The LTG blocks histological abnormalities induced by repeated administration of METH, which suggests a mechanism of LTG that protects against progressive pathophysiology in schizophrenia.

The glutaminergic, GABAergic, dopaminergic but not cholinergic neurons are susceptible to anaesthesia-induced cell death in the rat developing brain

Neuronal cell death induced by anaesthetics in the developing brain was evident in previous pre-clinical studies. However, the neuronal cell types involved in anaesthesia-induced neuronal cell death remains elusive. The aim of this study was to investigate glutamatergic, GABAergic, cholinergic and dopaminergic neuronal cell apoptosis induced by anaesthetic exposure in specific brain regions in rats. Separate cohorts of 7-day-old Sprague Dawley (SD) rat pups were randomly assigned to two groups: Naive and anaesthetics alone (70% nitrous oxide and 0.75% isoflurane exposure for 6 h). The brains were sectioned and the slices that contained the basal forebrain, substantia nigra, cornu ammonis area 1 (CA1) subarea of hippocampus or cingulate cortex were selected and subsequently subjected to double-labelled fluorescent immunohistochemistry for choline acetyltransferase, dopamine, vesicular glutamate transporter 1 (vGLUT1) or glutamic acid decarboxylase 67 (GAD67) together with caspase 3, respectively. Compared to the naive control, anaesthetic exposure significantly increased the number of caspase-3 positive cells in the CA1 subarea of hippocampus, cingulate cortex, and substantia nigra, but not in the basal forebrain. 54% and 14% of apoptotic cells in the CA1 subarea of hippocampus were GABAergic and glutamatergic neurons respectively. In the cingulate cortex, 30% and 37% of apoptotic cells were GABAergic and glutamatergic neurons respectively. In the substantia nigra, 22% of apoptotic cells were dopaminergic neurons. Our data suggests, anaesthetic exposure significantly increases neuroapoptosis of glutamatergic, GABAergic and dopaminergic neurons in the developing brain but not that of the cholinergic neurons in the basal forebrain.

Effect of Naoling decoction on iNOS expression in hippocampal CA3 region in rats with synthetic Alzheimer's disease

To observe the effect of Naoling decoction on the expression of iNOS in hippocamal CA3 region in rats with Alzheimer's disease (AD), and to explore the potential mechanism. Forty SD rats were classified into 5 groups: a normal group, a sham-operated group, an AD group, a Naoling decoction group, and a Naofukang group. The Alzheimer's disease model was established by injecting Aβ1-42 into the hippocamal in the rats. Expression of iNOS in the CA3 region was measured with immunohistochemical staining. Compared with the normal group, the expression of iNOS protein in the hippocampal CA3 fields in the AD group increased (P<0.05). Naoling decoction decreased the iNOS expression. Naoling decoction can significantly reduce the expression of iNOS in the AD model rats, suggesting that Naoling decoction can be used for AD rats.

Increased αB-crystallin in hypothalamic paraventricular nucleus of rats with myocardial infarction

The hypothalamus plays an important role in maintaining a homeostasis of the body against stress response. In particular, the paraventricular nucleus of the hypothalamus is a critical region for disorders related to the autonomic nervous system, such as congestive heart failure and hypertension. αB-crystallin is a family of heat shock proteins that are widely expressed in the brain, including in glial cells, astrocytes, oligodendrocytes, and neurons. Many studies have demonstrated that expression level of αB-crystallin is up-regulated and involved in protecting cells from pathological conditions. In the present study, we examined the expression and potential role of αB-crystallin in the paraventricular nucleus (PVN) regions of rats with myocardial infarction (MI). Our results demonstrate that mRNA encoding αB-crystallin and protein for both native and phosphorylate forms (Ser-59) of αB-crystallin was significantly increased in the PVN during MI.