RESUMEN
Childhood and adolescence are sensitive periods of development, marked by high brain maturation and plasticity. Exposure to early life stress, such as social isolation, is able to prompt changes in sensitive brain circuitries, essentially in the mesolimbic dopaminergic system and increase the risk for addictive behaviors later in life. Post-weaning social isolation can stimulate the consumption of rewarding substances, like drugs of abuse and palatable foods. However, most studies analyze long periods of social isolation and very little is known about the effects of a brief social isolation in a sensitive period of development and its association with palatable food on the reward system sensitization. Furthermore, females are more susceptible to the reinforcing effect of drugs than males. Therefore, the aim of this study was to analyze the effects of a short post-weaning social isolation combined with a free access to a chronic high sugar diet (HSD) on the dopaminergic system, oxidative status and behavioral response to an amphetamine-like drug in adulthood. We used female Wistar rats that were socially isolated from post-natal days (PD) 21 to 35 and received free access to a HSD until PD 60. On PD 65, animals were submitted to a challenge with diethylpropion (DEP), an amphetamine-like drug and different responses were analyzed: locomotor activity, immmunocontent of dopamine related proteins, and the oxidative status in the striatum, before and after the DEP challenge. We showed that a short post-weaning social isolation (SI) increased the locomotor response to DEP, when compared with previous saline administration. Social isolation also increased dopamine transporter, tyrosine hydroxylase, and decreased dopamine D2 receptor immunocontent. Additionally, SI increased the overall oxidative status parameters after the challenge with DEP. Interestingly, the exposure to a HSD prevented the SI effects on locomotor response, but did not interfere in the dopaminergic parameters evaluated, despite having modified some oxidative parameters. This study showed for the first time that a short post-weaning social isolation was able to induce long-term changes in the striatal dopaminergic system and increased the response to psychostimulants. These results emphasize the importance of stressful experiences during a short period of development on programming susceptibility to psychostimulants later in life.
Asunto(s)
Anfetamina/farmacología , Estimulantes del Sistema Nervioso Central/farmacología , Dopamina/metabolismo , Aislamiento Social , Trastornos Relacionados con Sustancias/fisiopatología , Animales , Animales Recién Nacidos , Catalasa/metabolismo , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Femenino , Fluoresceínas/metabolismo , Preferencias Alimentarias/efectos de los fármacos , Preferencias Alimentarias/fisiología , Glutatión Peroxidasa/metabolismo , Locomoción/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Receptores Dopaminérgicos/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Tamoxifen (TAM) is a selective estrogen receptor modulator (SERM) used in the treatment of breast cancer; however many women complain of weight gain during TAM treatment. The anorectic effects of estradiol (E) and TAM are well known, although the effects of E on the consumption of palatable food are controversial and there is no information regarding the effects of TAM on palatable food consumption. The aim of this study was to investigate the effects of chronic treatment with estradiol and/or tamoxifen on feeding behavior in ovariectomized rats exposed to standard chow and palatable foods (Froot Loops® or chocolate). Additionally, parameters such as body weight, uterine weight, lipid profile and plasma glucose were also measured. Wistar rats were ovariectomized (OVX) and subsequently injected (ip.) for 40 days with: E, TAM, E+TAM or vehicle (OVX and SHAM - controls). Behavioral tests were initiated 25 days after the start of treatment. Froot Loops® consumption was evaluated in a novel environment for 3 min. Standard chow intake was evaluated for two days and chocolate intake for 7 days in the home cage in a free choice model (chocolate or standard chow). Rats injected with E, TAM and E+TAM groups showed a reduction in body weight and standard chow intake, compared with control groups. With regard to palatable food intake, the E, TAM and E+TAM groups demonstrated increased consumption of Froot Loops®, compared with the SHAM and OVX groups. In contrast, all groups increased their consumption of chocolate, compared with standard chow; however the E group consumed more chocolate than the OVX, TAM and E+TAM groups. Despite these differences in chocolate consumption, all groups showed the same caloric intake during the chocolate exposure period; however the TAM and E+TAM groups presented decreased body weight. Treatment with estradiol and tamoxifen showed a favorable lipid profile with low levels of TC, LDL, LDL/HDL ratio and lower levels of plasma glucose. The E group presented high levels of TG and HDL, when compared with the TAM and E+TAM groups. Taken together, results suggest that TAM acted in an estrogen-like manner on the majority of parameters analyzed. However, tamoxifen acts in a different manner depending on the type of palatable food and the exposure. In addition, the TAM group demonstrated weight loss, compared with other groups independently of the type of food presented (palatable food or standard chow), showing a low caloric efficiency.
Asunto(s)
Glucemia/metabolismo , Estradiol/farmacología , Conducta Alimentaria/efectos de los fármacos , Preferencias Alimentarias/efectos de los fármacos , Lípidos/sangre , Tamoxifeno/farmacología , Animales , Peso Corporal/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Estradiol/administración & dosificación , Femenino , Ovariectomía , Ratas , Moduladores Selectivos de los Receptores de Estrógeno/farmacología , Tamoxifeno/administración & dosificación , Útero/efectos de los fármacosRESUMEN
This study examined the effects of two chronic stress regimens upon depressive-like behavior, A(1) and A(2A) adenosine receptor binding and immunocontent. Male rats were subjected to unpredictable chronic mild stress (UCMS) or to chronic restraint stress (CRS) for 40 days. Subsequently, depressive-like behaviors (forced swimming and consumption of sucrose) were evaluated, and A(1) adenosine or A(2A) adenosine receptors were examined in the hippocampus or striatum, respectively. UCMS animals demonstrated depressive-related behaviors (decrease in sucrose consumption and increased immobility in the forced swimming test). This group also presented increased A(1) adenosine receptor binding and immunoreactivity in hippocampus, as well as increased striatal A(2A) adenosine receptor binding in the striatum, without alteration in immunoreactivity. Conversely, the chronic restraint stress group displayed only an increase in A(1) adenosine receptor binding and no alteration in the other parameters evaluated. We suggest that the alteration in adenosine receptors, particularly the upregulation of striatal A(2A) adenosine receptors following UCMS, could be associated with depressive-related behavior.
Asunto(s)
Depresión/etiología , Depresión/patología , Hipocampo/metabolismo , Receptor de Adenosina A1/metabolismo , Receptor de Adenosina A2A/metabolismo , Estrés Psicológico/complicaciones , Adenosina Desaminasa/farmacología , Análisis de Varianza , Animales , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Hipocampo/efectos de los fármacos , Técnicas In Vitro , Masculino , Unión Proteica/efectos de los fármacos , Purinérgicos/farmacocinética , Ratas , Ratas Wistar , Sacarosa/administración & dosificación , Edulcorantes/administración & dosificación , Natación/psicología , Factores de Tiempo , Tritio/farmacocinética , Xantinas/farmacocinéticaRESUMEN
Morphine exposure during the neonatal period can promote changes in pain signaling pathways that can be expressed as an increased nociceptive response in adult life. Glutamate is the major excitatory neurotransmitter in primary afferent terminals and plays a critical role in normal spinal excitatory synaptic transmission. Considering the importance of a better understanding of the mechanisms that underlie nociceptive changes throughout the life course, the aim of this study was investigate the effects of repeated morphine administration at postnatal days 8 (P8) to 14 (P14) on glutamate uptake in spinal synaptosomes at P30 and P60. The morphine group showed decreased [3H]-glutamate uptake as compared to control groups in both P30 and P60. These findings suggest that morphine exposure in early life leads to changes in glutamatergic signaling at least until the 60th day of age, which may lead to increased levels of glutamate in the spinal synaptic cleft and, consequently, an increased nociceptive response in adult life. Thus, this study highlights the importance of conducting research in this field to provide a comprehensive knowledge of the long-term effects of early-life morphine treatment on nociceptive pathways.
Asunto(s)
Envejecimiento/metabolismo , Ácido Glutámico/metabolismo , Morfina/administración & dosificación , Neuronas/metabolismo , Médula Espinal/metabolismo , Sinaptosomas/metabolismo , Envejecimiento/efectos de los fármacos , Animales , Animales Recién Nacidos , Masculino , Neuronas/efectos de los fármacos , Neurotransmisores/metabolismo , Ratas , Ratas Wistar , Médula Espinal/efectos de los fármacos , Sinaptosomas/efectos de los fármacosRESUMEN
This study was undertaken to evaluate the effects of chronic variate stress and lithium treatment on glutamatergic activity and neuronal vulnerability of rat hippocampus. Male Wistar rats were simultaneously treated with lithium and submitted to a chronic variate stress protocol during 40 days, and afterwards the hippocampal glutamatergic uptake and release, measured in slices and synaptosomes, were evaluated. We observed an increased synaptosomal [(3)H]glutamate uptake and an increase in [(3)H]glutamate stimulated release in hippocampus of lithium-treated rats. Chronic stress increased basal [(3)H]glutamate release by synaptosomes, and decreased [(3)H]glutamate uptake in hippocampal slices. When evaluating cellular vulnerability, both stress and lithium increased cellular death after oxygen and glucose deprivation (OGD). We suggest that the manipulation of glutamatergic activity induced by stress may be in part responsible for the neuroendangerment observed after stress exposure, and that, in spite of the described neuroprotective effects of lithium, it increased the neuronal vulnerability after OGD.
Asunto(s)
Muerte Celular/efectos de los fármacos , Glucosa/metabolismo , Ácido Glutámico/metabolismo , Hipocampo/efectos de los fármacos , Hipoxia/metabolismo , Compuestos de Litio/farmacología , Estrés Fisiológico , Animales , Enfermedad Crónica , Hipocampo/enzimología , Hipocampo/metabolismo , Hipocampo/patología , L-Lactato Deshidrogenasa/metabolismo , Masculino , Necrosis , Ratas , Ratas WistarRESUMEN
In this study, we examined the effects of two chronic stress regimens upon anxiety-like behavior, Na(+), K(+)-ATPase activity and immunocontent, and oxidative stress parameters (antioxidant enzymes and reactive oxygen species production) in the amygdala. Male rats were subjected to chronic unpredictable and to chronic restraint stress for 40 days. Subsequently, anxiety-like behavior was examined. Both stressed groups presented increased anxiety-like behavior. Reduced amygdalal Na(+), K(+)-ATPase activity in the synaptic plasma membranes was also observed, without alterations in the amygdala immunocontent. In addition, when analyzing oxidative stress parameters, only superoxide dismutase activity was decreased in the amygdala of animals subjected to unpredictable stress. We conclude that both models of chronic stress lead to anxiety-like behavior and decreased amygdalal Na(+), K(+)-ATPase activity, which appears not to be related to oxidative imbalance. The relationship between this decreased activity and anxiety-like behavior remains to be studied.
Asunto(s)
Amígdala del Cerebelo/enzimología , Conducta Animal/fisiología , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Estrés Psicológico/enzimología , Animales , Ansiedad/etiología , Masculino , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas WistarRESUMEN
Previous studies have shown sex-specific oxidative changes in spinal cord of rats submitted to chronic stress, which may be due to gonadal hormones. Here, we assessed total radical-trapping potential (TRAP), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and lipid peroxidation (evaluated by the TBARS test) in the spinal cord of ovariectomized (OVX) female rats. Female rats were subjected to OVX, and half of the animals received estradiol replacement. Animals were subdivided into controls and chronically stressed (for 40 days). Our findings demonstrate that chronic stress decreased TRAP, and increased SOD activity in spinal cord homogenates from ovariectomized female rats and had no effect on GPx activity. On the other hand, groups receiving 17ß-estradiol replacement presented a decreased GPx activity, but no alteration in TRAP and in SOD activity. No differences in the TBARS test were found in any of the groups analyzed. In conclusion, our results support the idea that chronic stress induces an imbalance between SOD and GPx activities, additionally decreasing TRAP. Estradiol replacement did not reverse the effects of chronic stress, but induced a decrease in GPx activity. Therefore, estradiol replacement in ovariectomized chronically stressed rats could make the spinal cord more susceptible to oxidative injury.
Asunto(s)
Estradiol/farmacología , Estrés Oxidativo/efectos de los fármacos , Restricción Física/fisiología , Médula Espinal/metabolismo , Estrés Psicológico/fisiopatología , Animales , Femenino , Glutatión Peroxidasa/metabolismo , Peroxidación de Lípido/efectos de los fármacos , Ovariectomía , Ovario/fisiología , Ratas , Ratas Wistar , Médula Espinal/efectos de los fármacos , Superóxido Dismutasa/metabolismoRESUMEN
Caffeine is widely consumed in beverages and food, and its consumption in high doses is associated with anxiety increase. Stress situations are often associated to coffee consumption, and have a strong influence on oxidative DNA damage. As there are sex-specific differences in many metabolic, neurochemical and behavioral aspects, the aim of this study is to verify the interaction between chronic consumption of caffeine and chronic stress on anxiety and DNA breaks in the hippocampus on male and female rats. Wistar rats were submitted to restraint stress for at least 50 days. The diet consisted of standard rat chow and caffeine 0.3 or 1 g/L in drinking water "ad libitum" as the only drinking source. Controls received tap water. Anxiety-like behavior and DNA breaks in the hippocampus were evaluated. Caffeine consumption and chronic stress increased anxiety-like behavior as well as DNA breaks in the hippocampus of male rats. No effect on these parameters was observed in females. These results may be related to the presence of estradiol, which may have anxiolytic and neuroprotective properties.
Asunto(s)
Ansiedad/fisiopatología , Cafeína/administración & dosificación , Estimulantes del Sistema Nervioso Central/administración & dosificación , Roturas del ADN , Hipocampo/química , Estrés Fisiológico , Estrés Psicológico/fisiopatología , Glándulas Suprarrenales/anatomía & histología , Análisis de Varianza , Animales , Conducta Animal , Cafeína/efectos adversos , Cafeína/metabolismo , Estimulantes del Sistema Nervioso Central/efectos adversos , Estimulantes del Sistema Nervioso Central/metabolismo , Corticosterona/sangre , Conducta Exploratoria , Femenino , Locomoción , Masculino , Aprendizaje por Laberinto , Tamaño de los Órganos , Ratas , Ratas Wistar , Restricción Física , Caracteres SexualesRESUMEN
We studied the effect of chronic caffeine on parameters related to oxidative stress in different brain regions of stressed and non-stressed rats. Wistar rats were divided into three groups: control (receiving water), caffeine 0.3 g/L and caffeine 1.0 g/L (in the drinking water). These groups were subdivided into non-stressed and stressed (repeated restraint stress during 40 days). Lipid peroxide levels and the total radical-trapping potential were assessed, as well as antioxidant enzyme activities superoxide dismutase, gluthatione peroxidase, and catalase in hippocampus, striatum and cerebral cortex. Results showed interactions between stress and caffeine, especially in the cerebral cortex, since caffeine increased the activity of some antioxidant enzymes, but not in stressed animals. We concluded that chronic administration of caffeine led, in some cases, to increased activity of antioxidant enzymes. However, these effects were not observed in the stressed animals.
Asunto(s)
Antioxidantes/metabolismo , Cafeína/farmacología , Estrés Oxidativo , Estrés Psicológico/metabolismo , Animales , Catalasa/metabolismo , Corteza Cerebral/metabolismo , Cuerpo Estriado/metabolismo , Glutatión Peroxidasa/metabolismo , Hipocampo/metabolismo , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Restricción Física , Superóxido Dismutasa/metabolismo , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
Glutamate is an excitatory neurotransmitter involved in neuronal plasticity and neurotoxicity. Chronic stress produces several physiological changes on the spinal cord, many of them presenting sex-specific differences, which probably involve glutamatergic system alterations. The aim of the present study was to verify possible effects of exposure to chronic restraint stress and 17beta-estradiol replacement on [3H]-glutamate release and uptake in spinal cord synaptosomes of ovariectomized (OVX) rats. Female rats were subjected to OVX, and half of the animals received estradiol replacement. Animals were subdivided in controls and chronically stressed. Restraint stress or estradiol had no effect on [3H]-glutamate release. The chronic restraint stress promoted a decrease and 17beta-estradiol induced an increase on [3H]-glutamate uptake, but the uptake observed in the restraint stress +17beta-estradiol group was similar to control. Furthermore, 17beta-estradiol treatment caused a significant increase in the immunocontent of the three glutamate transporters present in spinal cord. Restraint stress had no effect on the expression of these transporters, but prevented the 17beta-estradiol effect. We suggest that changes in the glutamatergic system are likely to take part in the mechanisms involved in spinal cord plasticity following repeated stress exposure, and that 17beta-estradiol levels may affect chronic stress effects in this structure.
Asunto(s)
Estradiol/farmacología , Ácido Glutámico/metabolismo , Restricción Física , Médula Espinal/efectos de los fármacos , Estrés Psicológico/metabolismo , Animales , Enfermedad Crónica , Transportador 1 de Aminoácidos Excitadores/metabolismo , Transportador 2 de Aminoácidos Excitadores/metabolismo , Transportador 3 de Aminoácidos Excitadores/metabolismo , Femenino , Ovariectomía , Ratas , Ratas Wistar , Médula Espinal/metabolismo , Sinaptosomas/metabolismoRESUMEN
Anorectic effects of caffeine are controversial in the literature, while stress and obesity are growing problems in our society. Since many stressed people are coffee drinkers, the objective of the present study was to evaluate the effect of stress and chronic administration of caffeine on feeding behavior and body weight in male and female rats. Wistar rats (both males and females) were divided into 3 groups: control (receiving water), caffeine 0.3 g/L and caffeine 1.0 g/L (in the drinking water). These groups were subdivided into non-stressed and stressed (repeated-restraint stress for 40 days). During the entire treatment, chow consumption was monitored and rats were weighed monthly. Afterwards, feeding behavior was evaluated during 3-min trials in food-deprived and ad libitum fed animals and also in repeated exposures, using palatable food (Froot Loops and Cheetos). Chronic administration of caffeine did not affect rat chow consumption or body weight gain, but diminished the consumption of both salty (Cheetos) and sweet (Froot Loops) palatable food. In the repeated trial tests, stress diminished savory snack consumption in the later exposures [I.S. Racotta, J. Leblanc, D. Richard The effect of caffeine on food intake in rats: involvement of corticotropin-releasing factor and the sympatho-adrenal system. Pharmacol Biochem Behav. 1994, 48:887-892; S.D. Comer, M. Haney, R.W. Foltin, M.W. Fischman Effects of caffeine withdrawal on humans living in a residential laboratory. Exp Clin Psychopharmacol. 1997, 5:399-403; A. Jessen, B. Buemann, S. Toubro, I.M. Skovgaard, A. Astrup The appetite-suppressant effect of nicotine is enhanced by caffeine. Diab Ob Metab. 2005, 7:327-333; J.M. Carney Effects of caffeine, theophylline and theobromine on scheduled controlled responding in rats. Br J Pharmacol. 1982, 75:451-454] and caffeine diminished consumption of both palatable foods (savory and sweet) during the early and later exposures. Most responses to caffeine were stronger in females, and stress exposure influenced the effect. Neither chronic caffeine nor stress affected adrenal weight and plasma corticosterone levels of the rats. These observations suggest that chronic caffeine consumption may have sex-specific effects on palatable food ingestion.
Asunto(s)
Cafeína/administración & dosificación , Estimulantes del Sistema Nervioso Central/administración & dosificación , Conducta Alimentaria/efectos de los fármacos , Conducta Alimentaria/fisiología , Estrés Psicológico/fisiopatología , Adrenalectomía/métodos , Análisis de Varianza , Animales , Conducta Animal/efectos de los fármacos , Composición Corporal/efectos de los fármacos , Peso Corporal/efectos de los fármacos , Peso Corporal/fisiología , Corticosterona/sangre , Relación Dosis-Respuesta a Droga , Ingestión de Alimentos/efectos de los fármacos , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Masculino , Ratas , Ratas Wistar , Tiempo de Reacción/efectos de los fármacos , Tiempo de Reacción/fisiología , Restricción Física/métodos , Sales (Química)/metabolismo , Factores SexualesRESUMEN
Natural products, including those derived from plants, have largely contributed to the development of therapeutic drugs. Glutamate is the main excitatory neurotransmitter in the central nervous system and it is also considered a nociceptive neurotransmitter, by acting on peripheral nervous system. For this reason, in this study we investigated the effects of the hydroalcoholic extracts from Drymis winteri (polygodial and drimanial), Phyllanthus (rutin and quercetine), Jathopha elliptica (jatrophone), Hedyosmum brasiliense (13HDS), Ocotea suaveolens (Tormentic acid), Protium kleinii (alphabeta-amyrin), Citrus paradise (naringin), soybean (genistein) and Crataeva nurvala (lupeol), described as having antinociceptive effects, on glutamatergic transmission parameters, such as [(3)H]glutamate binding, [(3)H]glutamate uptake by synaptic vesicles and astrocyte cultures, and synaptosomal [(3)H]glutamate release. All the glutamatergic parameters were affected by one or more of these compounds. Specifically, drimanial and polygodial presented more broad and profound effects, requiring more investigation on their mechanisms. The putative central side effects of these compounds, via the glutamatergic system, are discussed.
Asunto(s)
Encéfalo/efectos de los fármacos , Ácido Glutámico/metabolismo , Extractos Vegetales/farmacología , Transmisión Sináptica/efectos de los fármacos , Sinaptosomas/metabolismo , Animales , Encéfalo/metabolismo , Diterpenos/farmacología , Flavanonas/farmacología , Genisteína/farmacología , Ácido Oleanólico/análogos & derivados , Ácido Oleanólico/farmacología , Ratas , Ratas Wistar , Sesquiterpenos/farmacología , Sinaptosomas/efectos de los fármacos , Triterpenos/farmacologíaRESUMEN
The excitotoxicity induced by QA has been related to its ability to increase free radical content and oxidative stress. In order to investigate the time course of toxicity and oxidative profile in the mice hippocampus following seizures induced by QA infusion (36.8 nM, i.c.v.), we evaluated the cellular damage (PI uptake assay), content of ROS formation (DCF assay) and the total radical antioxidant potential (TRAP) and reactivity (TAR) levels. The present results showed that a cellular damage occurred as early as 4 h after QA infusion coincident with an increase in the ROS contents, which returned to control levels after 24 h, while the cellular damage persisted for 72 h. There was a marked increased in the total antioxidant capacity at 8 h after QA infusion in both reactivity and potential levels. By 72 h post-treatment, the TRAP levels decreased, but the TAR levels remained augmented. Therefore, the delayed and persistent increase in the antioxidant capacity after QA insult may be a cellular adaptative response, probably contributing to decrease the ROS levels in order to prevent the spreading of the cellular damage. Therefore, the increase in the QA level in the brain ventricle may induce oxidative stress, which is followed by a persistent response in the antioxidant system in the hippocampus. The present study may, therefore, contribute to elucidate the mechanism of the brain dysfunction in patients with several neurological disorders involving elevation of QA in the CSF.
Asunto(s)
Encefalitis/metabolismo , Hipocampo/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Estrés Oxidativo/fisiología , Ácido Quinolínico/efectos adversos , Complejo SIDA Demencia/complicaciones , Complejo SIDA Demencia/metabolismo , Complejo SIDA Demencia/fisiopatología , Animales , Antioxidantes/metabolismo , Células Cultivadas , Modelos Animales de Enfermedad , Encefalitis/inducido químicamente , Encefalitis/fisiopatología , Radicales Libres/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/fisiopatología , Inyecciones Intraventriculares , Masculino , Ratones , Degeneración Nerviosa/inducido químicamente , Degeneración Nerviosa/metabolismo , Degeneración Nerviosa/fisiopatología , Enfermedades Neurodegenerativas/inducido químicamente , Enfermedades Neurodegenerativas/fisiopatología , Estrés Oxidativo/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismo , Convulsiones/etiología , Convulsiones/metabolismo , Convulsiones/fisiopatología , Factores de Tiempo , Regulación hacia Arriba/fisiologíaRESUMEN
Natural products including those derived from plants, have over the years greatly contributed to the development of therapeutic drugs. Polygodial and drimanial are sesquiterpenes isolated from the bark of the plant Drymis Winteri (Winteraceae) that exhibit antinociceptive properties. Since peripheral glutamate presents nociceptive actions, in this study it was investigated the effects of hydroalcooholic extracts from Drymis winteri (polygodial and drimanial) on the glutamatergic system in rat brain. Polygodial and drimanial inhibited glutamate uptake by astrocytes, as well as by cortical, hippocampal and striatal slices, and increased synaptosomal glutamate release. These concurrent effects would predispose to an increase in the extracellular glutamate concentrations, leading to possible neurotoxic effects (excitotoxicity) of these natural compounds, which would suggest the need for some caution in their therapeutic application.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Encéfalo/efectos de los fármacos , Ácido Glutámico/metabolismo , Sesquiterpenos/farmacología , Animales , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Transporte Biológico , Encéfalo/metabolismo , Células Cultivadas , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Técnicas In Vitro , Extractos Vegetales/farmacología , Ratas , Ratas Wistar , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo , WinteraceaeRESUMEN
The excitatory amino acids (EAAs) transporters regulate the balance between physiological and pathological signaling over stimulation of the glutamatergic system pathway. The effect of transportable substrates and glutamate (Glu) receptor agonists on Glu uptake in neuronal cells was assessed at different conditions. Cells pre-incubated with Glu, L- or D-aspartate (Asp) and washed presented an inhibition on [(3)H]-Glu uptake and this effect was not mimicked by Glu receptors agonists. The effects of L- and D-Asp were not altered by the presence of N-methyl-d-aspartate (NMDA) receptor antagonists. Thus, the reduction on Glu uptake induced by EAAs is probably linked to the transporter activity. In contrast, the presence of NMDA or (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (SR-ACPD) during the pre-incubation and the [(3)H]-Glu uptake assay period increased Glu uptake, whilst kainic acid (KA) had no effect. The NMDA effect was not altered by its antagonists (+/-)-2-amino-5-phosphonopentanoic acid (AP-5) or dizocilpine (MK-801). The SR-ACPD effect was due to the activation of metabotropic Glu receptor, since it was abolished by its antagonist, L(+/-)-2-amino-3-phosphonopropionic acid (L-AP3). Thus, the current studies suggest that the neuronal EAAs transporter is regulated in different manner by transportable substrates and Glu receptor agonists. The possible involvement of this modulation after certain neurotoxicity insults is discussed.
Asunto(s)
Sistema de Transporte de Aminoácidos X-AG/metabolismo , Agonistas de Aminoácidos Excitadores/farmacología , Neuronas/efectos de los fármacos , Receptores de Glutamato/metabolismo , Sistema de Transporte de Aminoácidos X-AG/agonistas , Animales , Animales Recién Nacidos , Ácido Aspártico/farmacología , Células Cultivadas , Cerebelo/citología , Cicloleucina/análogos & derivados , Cicloleucina/farmacología , Maleato de Dizocilpina/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Antagonistas de Aminoácidos Excitadores/farmacología , Ligandos , N-Metilaspartato/farmacología , Naftalenos , Neuronas/metabolismo , Fármacos Neuroprotectores/farmacología , Oxepinas , Ratas , Ratas Wistar , Tritio/metabolismo , Valina/análogos & derivados , Valina/farmacologíaRESUMEN
N-Methyl-D-aspartate (NMDA) preconditioning is evoked by subtoxic concentrations of NMDA (50 microM), which has been shown previously to lead to transient resistance to subsequent lethal dose of glutamate or NMDA in cultured neurons. The purpose of this study was to investigate the participation of adenosine A1 and A2A receptors on NMDA preconditioning against glutamate-induced cellular damage in cerebellar granule cells. NMDA preconditioning prevented the stimulatory effect induced by glutamate on AMP hydrolysis, but not on ADP hydrolysis. The neuroprotection evoked by NMDA preconditioning against glutamate-induced cellular damage was prevented by the presence of adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT, 100 nM), but not by the adenosine A2A receptors antagonist, (4-(2[7-amino-2-(2-furyl {1,2,4}-triazolo{2,3-a{1,3,5}triazian-5-yl-aminoethyl)phenol (ZM 241385, 50 nM). Interestingly, a long-term treatment with CPT or ZM 241385 alone protected cells against glutamate-induced neurotoxicity. Moreover, the functionality of adenosine A1 receptor was not affected by NMDA preconditioning, but this treatment promoted adenosine A2A receptor desensitization, measured by cAMP accumulation. Taken together, the results described herein suggest that the neuroprotection evoked by NMDA preconditioning against cellular damage elicited by glutamate occurs through mechanisms involving adenosine A2A receptors desensitization co-operating with adenosine A1 receptors activation in cerebellar granule cells.
Asunto(s)
Cerebelo/citología , Agonistas de Aminoácidos Excitadores/farmacología , Ácido Glutámico/toxicidad , N-Metilaspartato/farmacología , Neuronas/efectos de los fármacos , Receptores Purinérgicos P1/fisiología , Adenosina Difosfato/metabolismo , Adenosina Trifosfatasas/metabolismo , Animales , Animales Recién Nacidos , Muerte Celular/efectos de los fármacos , Células Cultivadas , AMP Cíclico/metabolismo , Antagonismo de Drogas , Hidrólisis/efectos de los fármacos , Neuronas/fisiología , Agonistas del Receptor Purinérgico P1 , Antagonistas de Receptores Purinérgicos P1 , Ratas , Ratas Wistar , Teofilina/análogos & derivados , Teofilina/farmacología , Triazinas/farmacología , Triazoles/farmacologíaRESUMEN
Glutamatergic mechanisms are thought to be involved in stress-induced changes of brain function, especially in the hippocampus. We hypothesized that alterations caused by the hormonal changes associated with chronic and acute stress may affect glutamate uptake and release from hippocampal synaptosomes in Wistar rats. It was found that [3H]glutamate uptake and release by hippocampal nerve endings, when measured 24 h after 1 h of acute restraint, presented no significant difference. The exposure to repeated restraint stress for 40 days increased neuronal presynaptic [3H]glutamate uptake as well as basal and K+-stimulated glutamate release when measured 24 h after the last stress session. Chronic treatment also caused a significant decrease in [3H]glutamate binding to hippocampal membranes. We suggest that changes in the glutamatergic system are likely to take part in the mechanisms involved in nervous system plasticity following repeated stress exposure.
Asunto(s)
Ácido Glutámico/metabolismo , Hipocampo/fisiología , Estrés Psicológico/metabolismo , Sinaptosomas/metabolismo , Animales , Transporte Biológico , Masculino , Ratas , Ratas Wistar , Valores de Referencia , Restricción FísicaRESUMEN
PURPOSE: N-methyl D-aspartate (NMDA) preconditioning has been used to prevent cellular death induced by glutamate or NMDA in cultured neurons. Quinolinic acid (QA)-induced seizures are used to average NMDA receptors-evoked neurotoxicity in animal models. The purpose of this study was to investigate the potential neuroprotective effects of NMDA preconditioning against QA-induced seizures and hippocampal damage in vivo. METHODS: Mice were pretreated with nonconvulsant doses of NMDA for different times before i.c.v. QA infusion and observed for the occurrence of seizures. Hippocampal slices from mice were assayed to measure cellular viability. RESULTS: NMDA preconditioning presented 53% protection against QA-induced seizures, as well as QA-induced cellular death in the hippocampus. The NMDA receptor antagonist, MK-801, prevented the protection evoked by NMDA preconditioning. The adenosine A1 receptor antagonist, CPT, prevented the protection evoked by NMDA preconditioning against QA-induced seizures, but not against QA-induced hippocampal cellular damage. The adenosine A1 receptor agonist, CPA, did not mimic the NMDA preconditioning-evoked protective effects. CONCLUSIONS: These results suggest that in vivo preconditioning with subtoxic doses of NMDA protected mice against seizures and cellular hippocampal death elicited by QA, probably through mechanisms involving NMDA receptors operating with adenosine A1 receptors.
Asunto(s)
Apoptosis/efectos de los fármacos , Agonistas de Aminoácidos Excitadores/farmacología , Hipocampo/efectos de los fármacos , N-Metilaspartato/farmacología , Ácido Quinolínico , Convulsiones/inducido químicamente , Convulsiones/prevención & control , Animales , Apoptosis/fisiología , Maleato de Dizocilpina/farmacología , Relación Dosis-Respuesta a Droga , Agonistas de Aminoácidos Excitadores/administración & dosificación , Hipocampo/fisiología , Humanos , Masculino , Ratones , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , N-Metilaspartato/administración & dosificación , Neuronas/efectos de los fármacos , Neuronas/fisiología , Síndromes de Neurotoxicidad/etiología , Síndromes de Neurotoxicidad/prevención & control , Ácido Quinolínico/administración & dosificación , Ácido Quinolínico/farmacología , Receptores de N-Metil-D-Aspartato/efectos de los fármacosRESUMEN
In previous work we showed that phosphorylation of glial fibrillary acidic protein (GFAP), an astrocyte marker, is increased by glutamate in hippocampal slices from immature rats via a type II metabotropic receptor. In the present work we show that glutamate also stimulates GFAP phosphorylation in microslices prepared from immature cerebellar cortex, but by a different receptor mechanism from that observed in the hippocampus. Thus, in cerebellar microslices, NMDA consistently stimulated GFAP phosphorylation, whereas no effect of metabotropic or non-NMDA ionotropic agonists was observed. Glutamate and NMDA also stimulated GFAP phosphorylation in mixed neuronal/glial cell cultures from the cerebellum, although no effect of these agonists was observed in primary cultures of cerebellar astrocytes. In both models, the effects of glutamate and NMDA were dependent on external Ca(2+), were reversed by the NMDA receptor antagonist AP5 and were not blocked by tetrodotoxin. In the slice study the effect of NMDA was confined to a period starting with the first detectable expression of GFAP at 10 days and finishing at 16 days postnatal, as previously observed with metabotropic agonists in hippocampal slices. This period in the rat corresponds to the start of synaptogenesis when astrocyte hypertrophy is occurring. The results are discussed in the light of information in the literature on the occurrence of functional NMDA receptor subunits in glia.
Asunto(s)
Astrocitos/metabolismo , Cerebelo/crecimiento & desarrollo , Cerebelo/metabolismo , Proteína Ácida Fibrilar de la Glía/metabolismo , Ácido Glutámico/metabolismo , Neuronas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animales , Animales Recién Nacidos , Astrocitos/citología , Astrocitos/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Células Cultivadas , Cerebelo/citología , Técnicas de Cocultivo , Relación Dosis-Respuesta a Droga , Agonistas de Aminoácidos Excitadores/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Ácido Glutámico/farmacología , Filamentos Intermedios/efectos de los fármacos , Filamentos Intermedios/metabolismo , Masculino , N-Metilaspartato/farmacología , Neuronas/citología , Neuronas/efectos de los fármacos , Fosforilación/efectos de los fármacos , Terminales Presinápticos/efectos de los fármacos , Terminales Presinápticos/metabolismo , Ratas , Ratas Wistar , Receptores de N-Metil-D-Aspartato/agonistas , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidoresRESUMEN
Extracellular ATP and adenosine modulate synaptic transmission in hippocampal neurons. ATP released from neural cells is hydrolyzed to adenosine by a chain of ecto-nucleotidases. ATP diphosphohydrolase hydrolyses ATP and ADP nucleotides to AMP and 5'-nucleotidase hydrolyses AMP to adenosine. In this work, we investigated the ATPase and ADPase activities of ATP diphosphohydrolase in cultured hippocampal neurons. The apparent Michaelis-Menten constant (K(m)) was 233.9 +/- 14.6 and 221.8 +/- 63.6 microM, with a calculated maximal velocity (V(max), approximately) of 49.2 +/- 10.7 and 10.9 +/- 5.2 nmol Pi/mg protein/min for ATP and ADP, respectively. The horizontal straight line obtained in the competition plot indicated that only one active site is able to hydrolyze both substrates. Furthermore, we detected the presence of this enzyme using anti-CD39 antibody, which strongly stained the soma of pyramidal and bipolar neurons, but the neurites connecting the cell clusters were also immunopositive. This antibody recognized three bands with a molecular mass close to 95, 80 and 60kDa in immunoblotting analysis. The present results show, for the first time, the kinetic and immunocytochemical characterization of an ATP diphosphohydrolase in cultured hippocampal neurons. Probably, the widespread distribution of this enzyme on the surface of neurons in culture could reflect its functional importance in studies of synaptic plasticity hippocampal.