RESUMO
To contribute to research on female models of Alzheimer's disease (AD), our aim was to study the effect of intracerebroventricular (ICV) injection of streptozotocin (STZ) in female rats, and to evaluate a potential neuroprotective action of ovarian steroids against STZ. Female rats were either ovariectomized (OVX) or kept with ovaries (Sham) two weeks before ICV injections. Animals were injected with either vehicle (artificial cerebrospinal fluid, aCSF) or STZ (3 mg/kg) and separated into four experimental groups: Sham + aCSF, Sham + STZ, OVX + aCSF and OVX + STZ. Nineteen days post-injection, we assessed different behavioral aspects: burying, anxiety and exploration, object recognition memory, spatial memory, and depressive-like behavior. Immunohistochemistry and Immunoblot analyses were performed in the hippocampus to examine changes in AD-related proteins and neuronal and microglial populations. STZ affected burying and exploratory behavior depending on ovarian status, and impaired recognition but not spatial memory. STZ and ovariectomy increased depressive-like behavior. Interestingly, STZ did not alter the expression of ß-amyloid peptide or Tau phosphorylated forms. STZ affected the neuronal population from the Dentate Gyrus, where immature neurons were more vulnerable to STZ in OVX rats. Regarding microglia, STZ increased reactive cells, and the OVX + STZ group showed an increase in the total cell number. In sum, STZ partially affected female rats, compared to what was previously reported for males. Although AD is more frequent in women, reports about the effect of ICV-STZ in female rats are scarce. Our work highlights the need to deepen into the effects of STZ in the female brain and study possible sex differences.
Assuntos
Doença de Alzheimer , Ovariectomia , Estreptozocina , Animais , Feminino , Doença de Alzheimer/induzido quimicamente , Doença de Alzheimer/metabolismo , Ratos , Injeções Intraventriculares , Ratos Wistar , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Ovário/efeitos dos fármacos , Ovário/metabolismo , Depressão/induzido quimicamente , Depressão/metabolismo , Peptídeos beta-Amiloides/metabolismo , Memória Espacial/efeitos dos fármacosRESUMO
GH acts in numerous organs expressing the GH receptor (GHR), including the brain. However, the mechanisms behind the brain's permeability to GH and how this hormone accesses different brain regions remain unclear. It is well-known that an acute GH administration induces phosphorylation of the signal transducer and activator of transcription 5 (pSTAT5) in the mouse brain. Thus, the pattern of pSTAT5 immunoreactive cells was analyzed at different time points after IP or intracerebroventricular GH injections. After a systemic GH injection, the first cells expressing pSTAT5 were those near circumventricular organs, such as arcuate nucleus neurons adjacent to the median eminence. Both systemic and central GH injections induced a medial-to-lateral pattern of pSTAT5 immunoreactivity over time because GH-responsive cells were initially observed in periventricular areas and were progressively detected in lateral brain structures. Very few choroid plexus cells exhibited GH-induced pSTAT5. Additionally, Ghr mRNA was poorly expressed in the mouse choroid plexus. In contrast, some tanycytes lining the floor of the third ventricle expressed Ghr mRNA and exhibited GH-induced pSTAT5. The transport of radiolabeled GH into the hypothalamus did not differ between wild-type and dwarf Ghr knockout mice, indicating that GH transport into the mouse brain is GHR independent. Also, single-photon emission computed tomography confirmed that radiolabeled GH rapidly reaches the ventral part of the tuberal hypothalamus. In conclusion, our study provides novel and valuable information about the pattern and mechanisms behind GH transport into the mouse brain.
Assuntos
Encéfalo , Hormônio do Crescimento , Receptores da Somatotropina , Fator de Transcrição STAT5 , Animais , Fator de Transcrição STAT5/metabolismo , Fator de Transcrição STAT5/genética , Encéfalo/metabolismo , Hormônio do Crescimento/metabolismo , Camundongos , Receptores da Somatotropina/metabolismo , Receptores da Somatotropina/genética , Masculino , Camundongos Knockout , Camundongos Endogâmicos C57BL , Fosforilação , Plexo Corióideo/metabolismo , Hipotálamo/metabolismo , Injeções IntraventricularesRESUMO
Hypovolemia induced by hemorrhage is a common clinical complication, which stimulates vasopressin (AVP) secretion by the neurohypophysis in order to retain body water and maintain blood pressure. To evaluate the role of brain L-glutamate and angiotensin II on AVP secretion induced by hypovolemia we induced hemorrhage (â¼25% of blood volume) after intracerebroventricular (icv) administration of AP5, NBQX, or losartan, which are NMDA, AMPA, and AT1 receptor antagonists, respectively. Hemorrhage significantly increased plasma AVP levels in all groups. The icv injection of AP5 did not change AVP secretion in response to hemorrhage. Conversely, icv administration of both NBQX and losartan significantly decreased plasma AVP levels after hemorrhage. Therefore, the blockade of AMPA and AT1 receptors impaired AVP secretion in response to hemorrhage, suggesting that L-glutamate and angiotensin II acted in these receptors to increase AVP secretion in response to hemorrhage-induced hypovolemia.
Assuntos
Arginina Vasopressina , Hemorragia , Receptor Tipo 1 de Angiotensina , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico , Angiotensina II , Animais , Arginina Vasopressina/metabolismo , Pressão Sanguínea , Injeções Intraventriculares , Masculino , Ratos Wistar , Receptor Tipo 1 de Angiotensina/metabolismoRESUMO
AIM: The aim of this study was to assess the influence of adrenomedullary secretion on the plasma glucose, lactate, and free fatty acids (FFAs) during running exercise in rats submitted to intracerebroventricular (i.c.v.) injection of physostigmine (PHY). PHY i.c.v. was used to activate the central cholinergic system. METHODS: Wistar rats were divided into sham-saline (sham-SAL), sham-PHY, adrenal medullectomy-SAL, and ADM-PHY groups. The plasma concentrations of glucose, lactate, and FFAs were determined immediately before and after i.c.v. injection of 20 µL of SAL or PHY at rest and during running exercise on a treadmill. RESULTS: The i.c.v. injection of PHY at rest increased plasma glucose in the sham group, but not in the ADM group. An increase in plasma glucose, lactate, and FFAs mobilization from adipose tissue was observed during physical exercise in the sham-SAL group; however, the increase in plasma glucose was greater with i.c.v. PHY. Moreover, the hyperglycemia induced by exercise and PHY in the ADM group were blunted by ADM, whereas FFA mobilization was unaffected. CONCLUSION: These results indicate that there is a dual metabolic control by which activation of the central cholinergic pathway increases plasma glucose but not FFA during rest and exercise, and that this hyperglycemic response is dependent on adrenomedullary secretion.
Assuntos
Medula Suprarrenal/fisiologia , Fibras Colinérgicas/fisiologia , Metabolismo/fisiologia , Esforço Físico/fisiologia , Medula Suprarrenal/efeitos dos fármacos , Animais , Glicemia/efeitos dos fármacos , Fibras Colinérgicas/efeitos dos fármacos , Inibidores da Colinesterase/administração & dosagem , Inibidores da Colinesterase/farmacologia , Ácidos Graxos não Esterificados/sangue , Injeções Intraventriculares , Ácido Láctico/sangue , Masculino , Metabolismo/efeitos dos fármacos , Condicionamento Físico Animal , Fisostigmina/administração & dosagem , Fisostigmina/farmacologia , Ratos WistarRESUMO
BACKGROUND: Alzheimer's disease (AD) is characterized by cognitive impairment that eventually develops into dementia. Amyloid-beta (Aß) accumulation is a widely described hallmark in AD, and has been reported to cause olfactory dysfunction, a condition considered an early marker of the disease associated with injuries in the olfactory bulb (OB), the hippocampus (HIPP) and other odor-related cortexes. Adiponectin (APN) is an adipokine with neuroprotective effects. Studies have demonstrated that APN administration decreases Aß neurotoxicity and Tau hyperphosphorylation in the HIPP, reducing cognitive impairment. However, there are no studies regarding the neuroprotective effects of APN in the olfactory dysfunction observed in the Aß rat model. The aim of the present study is to determine whether the intracerebroventricular (i.c.v) administration of APN prevents the early olfactory dysfunction in an i.c.v Amyloid-beta1-42 (Aß1-42) rat model. Hence, we evaluated olfactory function by using a battery of olfactory tests aimed to assess olfactory memory, discrimination and detection in the Aß rat model treated with APN. In addition, we determined the number of cells expressing the neuronal nuclei (NeuN), as well as the number of microglial cells by using the ionized calcium-binding adapter molecule 1 (Iba-1) marker in the OB and, CA1, CA3, hilus and dentate gyrus (DG) in the HIPP. Finally, we determined Arginase-1 expression in both nuclei through Western blot. RESULTS: We observed that the i.c.v injection of Aß decreased olfactory function, which was prevented by the i.c.v administration of APN. In accordance with the olfactory impairment observed in i.c.v Aß-treated rats, we observed a decrease in NeuN expressing cells in the glomerular layer of the OB, which was also prevented with the i.c.v APN. Furthermore, we observed an increase of Iba-1 cells in CA1, and DG in the HIPP of the Aß rats, which was prevented by the APN treatment. CONCLUSION: The present study describes the olfactory impairment of Aß treated rats and evidences the protective role that APN plays in the brain, by preventing the olfactory impairment induced by Aß1-42. These results may lead to APN-based pharmacological therapies aimed to ameliorate AD neurotoxic effects.
Assuntos
Adiponectina/farmacologia , Doença de Alzheimer , Encéfalo/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Transtornos do Olfato , Peptídeos beta-Amiloides/toxicidade , Animais , Modelos Animais de Doenças , Injeções Intraventriculares , Masculino , Transtornos do Olfato/etiologia , Ratos , Ratos WistarRESUMO
Alamandine (Ala1-Arg2-Val3-Tyr4-Ile5-His6-Pro7), a heptapeptide hormone of the renin-angiotensin system (RAS), exerts its effects through the Mas-related G-protein coupled receptor of the type D, MrgD, which is expressed in different tissues, including the brain. In the present study, we tested the hypothesis that alamandine could attenuate the depression-like behavior observed in transgenic rats with low brain angiotensinogen, TGR (ASrAOGEN)680. Transgenic rats exhibited a significant increase in the immobility time in forced swim test, a phenotype reversed by intracerebroventricular infusion of alamandine. Pretreatment with D-Pro7-Ang-(1-7), a Mas/MrgD receptor antagonist, prevented the antidepressant-like effect induced by this peptide demonstrating, for the first time, that alamandine through MrgD receptor, can modulate depression-like behavior in TGR (ASrAOGEN)680. This result shows an action of alamandine which strengthens the importance of the counter-regulatory arms of the RAS in fight and treatment of neuropsychiatric diseases.
Assuntos
Angiotensinogênio/genética , Antidepressivos/farmacologia , Encéfalo/efeitos dos fármacos , Proteínas do Tecido Nervoso/fisiologia , Oligopeptídeos/farmacologia , Receptores Acoplados a Proteínas G/fisiologia , Angiotensina I/farmacologia , Angiotensinogênio/metabolismo , Animais , Encéfalo/metabolismo , Injeções Intraventriculares , Masculino , Proteínas do Tecido Nervoso/antagonistas & inibidores , Oligopeptídeos/administração & dosagem , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Ratos Transgênicos , Receptores Acoplados a Proteínas G/antagonistas & inibidores , Receptores Acoplados a Proteínas G/metabolismoRESUMO
Sex differences in the immune response can also affect the febrile response, particularly the fever induced by lipopolysaccharide (LPS). However, other pathogen-associated molecular patterns, such as zymosan A (Zym) and polyinosinic-polycytidylic acid (Poly I:C), also induce fever in male rats with a different time course of cytokine release and different mediators such as endothelin-1 (ET-1). This study investigated whether female sex hormones affect Zym- and Poly I:C-induced fever and the involvement of ET-1 in this response. The fever that was induced by Zym and Poly I:C was higher in ovariectomized (OVX) female rats compared with sham-operated female rats. Estrogen replacement in OVX females reduced Zym- and Poly I:C-induced fever. The ETB receptor antagonist BQ788 reversed the LPS-induced fever in cycling females but not in OVX females. BQ788 did not alter the fever that was induced by Zym or Poly I:C in either cycling or OVX females. These findings suggest that the febrile response in cycling females is lower, independently of the stimulus that is inducing it and is probably controlled by estrogen. Also, ET-1 seems to participate in the febrile response that was induced by LPS in males and cycling females but not in the LPS-induced fever in OVX females. Additionally, ET-1 was not involved in the febrile response that was induced by Zym or Poly I:C in females.
Assuntos
Endotelina-1/metabolismo , Febre/induzido quimicamente , Febre/metabolismo , Hormônios Esteroides Gonadais/metabolismo , Poli I-C/toxicidade , Zimosan/toxicidade , Animais , Endotelina-1/antagonistas & inibidores , Feminino , Injeções Intraventriculares , Masculino , Ovariectomia/tendências , Poli I-C/administração & dosagem , Ratos , Ratos Wistar , Zimosan/administração & dosagemRESUMO
Orexins-A (OrxA) and -B (OrxB) neuropeptides are synthesized by a group of neurons located in the lateral hypothalamus and adjacent perifornical area, which send their projections to the mesolimbic dopaminergic (DAergic) system including ventral tegmental area and nucleus accumbens (NAc), where orexin receptors are expressed. NAc plays a central role in reward-seeking behavior and drug abuse. NAc-neurons express dopamine-1 (D1R) and dopamine-2 (D2R) receptors. Orexins bind to their two cognate G-protein-coupled receptors, orexin-receptor type-1 (Orx1R) and type-2 (Orx2R). Orexin receptor signaling is involved in behaviors such as motivation and addiction. Orexin-containing neurons modulate DAergic activity that is key in synaptic plasticity induced by addictive drugs. However, the effect of OrxA on expression and content of DAergic receptors in NAc is unknown. The purpose of this study was to investigate whether OrxA can alter gene expression and protein levels of D1R/D2R in NAc. Gene expression was evaluated by real-time PCR analysis and protein levels by western blot in rats. The results show that intracerebroventricular (i.c.v.) injection of OrxA increases both gene transcription and protein content of D2R but fails to modify D1R. This effect was also confirmed with OrxA infusion in NAc/Shell. Our results demonstrate for the first time that OrxA induces up-regulation of gene and protein of D2R in NAc. These findings support the hypothesis that OrxA modulates the DAergic transmission and this may serve to understand how orexin signaling enhances DA responses at baseline conditions and in response to psychostimulants.
Assuntos
Neurônios Dopaminérgicos/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Orexinas/farmacologia , Receptores de Dopamina D1/genética , Receptores de Dopamina D2/genética , Animais , Neurônios Dopaminérgicos/citologia , Neurônios Dopaminérgicos/metabolismo , Regulação da Expressão Gênica , Injeções Intraventriculares , Masculino , Núcleo Accumbens/citologia , Núcleo Accumbens/metabolismo , Orexinas/metabolismo , Ligação Proteica , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Transdução de Sinais , Técnicas EstereotáxicasRESUMO
A nontransgenic rat model based on intracerebroventricular injection of streptozotocin (STZ) has been used as an animal model to investigate mechanisms associated to the late onset of sporadic Alzheimer's disease, such as anatomical and behavioral impairments. However, molecular aspects related to gene expression, mainly in the hippocampus, require more investigation. Thus, this study evaluated the early and late cognitive functions and hippocampal gene expression after STZ administration. Male Wistar rats were divided into 4 groups: STZ (injected bilaterally), control group for the early memory function evaluation (1 month after surgery = phase 1, same volume of vehicle), and the same treatment for the late memory function evaluation (4 months after surgery = phase 2). The animals were observed in the elevated plus maze to assess behaviors related to anxiety, riskassessment and fearrelated memories. The behavioral tests were followed by brain removal and hippocampal dissection for RNA extraction and qRTPCR to assess the expression levels of 4 Alzheimer's disease related genes: Mapt, Apoe, C3 and Ps1. Animals from both phases showed increased time percentage and number of entries into the open arms, indicating risk behavior associated with anxiety, and an increased time percentage in the center square for both exposures (retest) when compared to the control group, suggesting working memory impairment related to an aversive event. Statistical analyses indicated that the STZ group presented alterations in anxiety, memory and risk assessment responses. Additionally, one month after STZ administration, C3 gene assays revealed an increased expression. Therefore, current data indicate that neuroinflammatory events linked to the expression of pro inflammatory cytokines such as C3 are related to memory, anxiety and decision-making alterations.
Assuntos
Comportamento Animal/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Transtornos da Memória/tratamento farmacológico , Estreptozocina/farmacologia , Animais , Cognição/efeitos dos fármacos , Modelos Animais de Doenças , Hipocampo/metabolismo , Injeções Intraventriculares/métodos , Masculino , Transtornos da Memória/metabolismo , Memória de Curto Prazo/efeitos dos fármacos , Ratos Wistar , Estreptozocina/administração & dosagem , Estreptozocina/metabolismoRESUMO
Amyloid-ß (Aß) peptides play a significant role in the pathogenesis of Alzheimer's disease (AD). Neurotoxic effects promoted by Aß peptides involve glutamate transmission impairment, decrease of neurotrophic factors, mitochondrial dysfunction, oxidative stress, synaptotoxicity, and neuronal degeneration. Here, we assessed the early events evoked by Aß1-40 on the hippocampus. Additionally, we sought to unravel the molecular mechanisms of atorvastatin preventive effect on Aß-induced hippocampal damage. Mice were treated orally (p.o.) with atorvastatin 10 mg/kg/day during 7 consecutive days before the intracerebroventricular (i.c.v.) infusion of Aß1-40 (400 pmol/site). Twenty-four hours after Aß1-40 infusion, a reduced content of mature BDNF/proBDNF ratio was observed in Aß-treated mice. However, there is no alteration in synaptophysin, PSD-95, and doublecortin immunocontent in the hippocampus. Aß1-40 promoted an increase in reactive oxygen species (ROS) and nitric oxide (NO) generation in hippocampal slices, and atorvastatin prevented this oxidative burst. Mitochondrial OXPHOS was measured by high-resolution respirometry. At this time point, Aß1-40 did not alter the O2 consumption rates (OCR) related to phosphorylating state associated with complexes I and II, and the maximal OCR. However, atorvastatin increased OCR of phosphorylating state associated with complex I and complexes I and II, maximal OCR of complexes I and II, and OCR associated with mitochondrial spare capacity. Atorvastatin treatment improved mitochondrial function in the rodent hippocampus, even after Aß infusion, pointing to a promising effect of improving brain mitochondria bioenergetics. Therefore, atorvastatin could act as an adjuvant in battling the symptoms of AD to preventing or delaying the disease progression.