Repeated exposure of adolescent rats to oral methylphenidate does not induce behavioral sensitization or cross-sensitization to nicotine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reduction of enantioselectivity in the kinetic disposition and metabolism of verapamil in rats exposed to toluene

Toluene and verapamil are subject to extensive oxidative metabolism mediated by CYP enzymes, and their interaction can be stereoselective. In the present study we investigated the influence of toluene inhalation on the enantioselective kinetic disposition of verapamil and its metabolite, norverapamil, in rats. Male Wistar rats (n = 6 per group) received a single dose of racemic verapamil (10 mg/kg) orally at the fifth day of nose-only toluene or air (control group) inhalation for 6 h/day (25, 50, and 100 ppm). Serial blood samples were collected from the tail up to 6 h after verapamil administration. The plasma concentrations of verapamil and norverapamil enantiomers were analyzed by LC-MS/MS by using a Chiralpak AD column. Toluene inhalation did not influence the kinetic disposition of verapamil or norverapamil enantiomers (p > 0.05, Kruskal-Wallis test) in rats. The pharmacokinetics of verapamil was enantioselective in the control group, with a higher plasma proportion of the S-verapamil (AUC 250.8 versus 120.4 ng.h.mL(-1); p <= 0.05, Wilcoxon test) and S-norverapamil (AUC 72.3 versus 52.3 ng.h.mL(-1); p <= 0.05, Wilcoxon test). Nose-only exposure to toluene at 25, 50, or 100 ppm resulted in a lack of enantioselectivity for both verapamil and norverapamil. The study demonstrates the importance of the application of enantioselective methods in studies on the interaction between solvents and chiral drugs.

The semi-synthetic kaurane ent-16 alpha-methoxykauran-19-oic acid induces vascular relaxation and hypotension in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Antipanic procedures reduce the strychnine-facilitated wild running of rats

Wild running (WR) behavior of rats seen in response to intense acoustic stimulation of audiogenic seizure-paradigm is very similar to the panic flight and can be facilitated by subconvulsive doses of strychnine. The present work aimed to test whether antipanic procedures, such as dorsal periaqueductal gray (dPAG) lesion and imipramine treatments, affect the strychnine-facilitated WR. In study 1, six Wistar male adult rats with electrolytic lesion of dPAG had their WR completely blocked, whereas it was facilitated in 50% of sham-lesioned control rats by a dose of 0.5 mg/kg of strychnine administered intraperitoneal. This effect was not reproduced with a higher strychnine dose (1.0 mg/kg). In study 2, the effects of imipramine were investigated by testing 36 rats under a dose of strychnine that induces WR in 50% of subjects. They were assigned into three experimental groups: imipramine treatments of 5.0 and 10.0 mg/kg, and infusions of saline. All these treatments were subchronical with three intraperitoneal injections within 24h. Imipramine (10.0mg/kg) reduced the incidence of WR in comparison to the saline results. It is concluded that strychnine-facilitated WR is reduced by antipanic procedures and, therefore, can be viewed as a manifestation closely related to panic. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Correlation between the fighting rates of REM sleep-deprived rats and susceptibility to the 'wild running' of audiogenic seizures

Sleep-deprived rats exhibit defensive fighting as well as explosive flights very similar to the wild-running of audiogenic seizures. In order to determine why sleep deprivation is a common factor that facilitates both panic and convulsive manifestations, the present study was undertaken to investigate whether rats that display sleep deprivation-induced fighting (SDIF) are the same as those that are susceptible to audiogenic wild-running (WR). Twenty-eight male adult Wistar rats were divided into two groups assigned to two e-sleep deprivation for 5 days and had their SDIF evaluated in social experimental schemes. In the first, 18 subjects were submitted to REM grouping. After 1 week for recovery, their susceptibility to WR was tested in an acoustic stimulation trial ( 104 dB, 200 Hz, 60 S). Rats that did not present WR received a lactate infusion and were tested again by acoustic stimulation 40 min later. In the second experimental scheme, 10 subjects were initially evaluated for WR susceptibility and the number of SDIF was recorded in social grouping after I week. Three categories of WR-susceptibility were determined: WR-sensitive rats, intermediate WR-sensitive rats and WR-insensitive rats. T'he number of SDIF in each category was significantly different and there was a high positive correlation (r=0.89; Spearman test) between the number of SDIF and the level of WR-susceptibility. We conclude that the reasons why sleep deprivation exerts facilitatory effects on both panic and convulsive manifestations are due to overlappings of neural pathways responsible for both behavioral patterns and for the property of sleep deprivation to increase neuronal excitability. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Reduced pancreatic β-cell mass is associated with decreased FoxO1 and Erk1/2 protein phosphorylation in low-protein malnourished rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Increased pancreatic islet mass is accompanied by activation of the insulin receptor substrate-2/serine-threonine kinase pathway and augmented cyclin D(2) protein levels in insulin-resistant rats

It is well known that glucocorticoids induce peripheral insulin resistance in rodents and humans. Here, we investigated the structural and ultrastructural modifications, as well as the proteins involved in beta-cell function and proliferation, in islets from insulin-resistant rats. Adult male Wistar rats were made insulin resistant by daily administration of dexamethasone (DEX; 1mg/kg, i.p.) for five consecutive days, whilst control (CTL) rats received saline alone. Structure analyses showed a marked hypertrophy of DEX islets with an increase of 1.7-fold in islet mass and of 1.6-fold in islet density compared with CTL islets (P < 0.05). Ultrastructural evaluation of islets revealed an increased amount of secreting organelles, such as endoplasmic reticulum and Golgi apparatus in DEX islets. Mitotic figures were observed in DEX islets at structural and ultrastructural levels. Beta-cell proliferation, evaluated at the immunohistochemical level using anti-PCNA (proliferating cell nuclear antigen), showed an increase in pancreatic beta-cell proliferation of 6.4-fold in DEX islets compared with CTL islets (P < 0.0001). Increases in insulin receptor substrate-2 (IRS-2), phosphorylated-serine-threonine kinase AKT (p-AKT), cyclin D(2) and a decrease in retinoblastoma protein (pRb) levels were observed in DEX islets compared with CTL islets (P < 0.05). Therefore, during the development of insulin resistance, the endocrine pancreas adapts itself increasing beta-cell mass and proliferation, resulting in an amelioration of the functions. The potential mechanisms that underlie these events involve the activation of the IRS-2/AKT pathway and activation of the cell cycle, mediated by cyclin D(2). These adaptations permit the maintenance of glycaemia at near-physiological ranges.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28%, WKY = 64%, 3 days) and (SHR = 141%, WKY = 122%, 13 weeks). SHR had higher values of AP than WKY (174 ± 4 vs 111 ± 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28%, WKY = 36%) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19%, WKY = 15%). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18%, WKY = 19%), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.

Influence of the estrous cycle on the behavior of rats in the elevated T-maze

The elevated T-maze is an animal anxiety model which can discriminate between anxiety-like and fear-like behaviors. The estrous cycle is an important variable of the response in animal anxiety tests and is known to affect other models. The aim of the present study was to investigate the influence of the estrous cycle on behavior displayed in the elevated T-maze test. Seventeen male and 60 female rats were submitted to one session in this test, with the females being screened for the estrous cycle and divided into groups according to the various phases. The elevated T-maze had three arms of equal dimensions (50 cm x 10 cm), one enclosed by 40-cm high walls and perpendicular to the others, the apparatus being elevated 50cm above the floor. Each rat was placed in the end of the enclosed arm and the latency for it to leave this arm was recorded. These measurements were repeated three times separated by 30-s intervals (passive avoidance). After trial 3, each rat was placed at the distal end of the right open arm and the latency to exit this arm was recorded. Whenever latencies were greater than 300 s the trial was finished. The results demonstrated females in diestrus exhibited anxiety-like behaviors while females in metaestrus behaved in a similar way as the males. There were no differences between groups in fear-like behaviors. The results also indicate the elevated T-maze to be a sensitive test to measure anxiety. (C) 2004 Elsevier B.V. All rights reserved.

Prevention of renal ischemia/reperfusion injury in rats using acetylcysteine after anesthesia with isoflurane

OBJETIVO: Avaliar o efeito da N-acetilcisteína na proteção renal contra lesão de isquemia/reperfusão, quando administrada logo após a indução anestésica, em ratos anestesiados com isoflurano. MÉTODOS: Dezoito ratos Wistar machos pesando mais que 300g foram anestesiados com isoflurano. A jugular interna direita e a carótida esquerda foram dissecadas e canuladas. Os animais foram distribuídos aleatoriamente em GAcetil, recebendo N-acetilcisteína por via intravenosa, 300mg/kg, e GIsot, solução salina. Foi realizada nefrectomia direita e clampeamento da artéria renal esquerda por 45 min. Os animais foram sacrificados após 48h, sendo colhidas amostras sanguíneas após a indução anestésica e ao sacrifício dos mesmos para avaliar a creatinina sérica. Realizou-se histologia renal. RESULTADOS: A variação da creatinina foi 2,33mg/dL ± 2,21 no GAcetil e 4,38mg/dL ± 2,13 no GIsot (p=0,074). Dois animais apresentaram necrose tubular intensa no GAcetil, comparados a cinco no GIsot. Apenas GAcetil apresentou animais livres de necrose tubular (dois) e degeneração tubular (um). CONCLUSÃO: Após isquemia/reperfusão renais, os ratos aos quais se administrou N-acetilcisteína apresentaram menor variação na creatinina sérica e lesões renais mais leves que o grupo controle.

Influence of S(+)-ketamine analgesia in renal intraoperative ischemia: histological study in rats

OBJETIVO: Investigar, em ratos, o efeito da S(+)cetamina na histologia renal após hemorragia intra-operatória. MÉTODOS: Vinte ratos Wistar machos, anestesiados com pentobarbital sódico, foram divididos, aleatoriamente, em 2 grupos: G1 - controle (n=10) e G2 - S(+)cetamina (n=10), submetidos a hemorragia de 30% da volemia em 3 momentos (10% a cada 10 min) 60 min após anestesia. G2 recebeu S(+)cetamina, 15 mg. kg-1, i.m., 5 min após anestesia e 55 min antes do 1.º momento de hemorragia (M1). Foram monitorizadas a pressão arterial média (PAM), temperatura retal (T) e freqüência cardíaca. Os animais foram sacrificados (M4) 30 min após o 3.º momento de hemorragia (M3). Os rins e o sangue das hemorragias foram utilizados para estudo histológico e do hematócrito (Ht). RESULTADOS: Houve redução significativa da PAM, T e Ht. Na histologia, G1=G2 na dilatação tubular, congestão e necrose. A soma total dos escores foi significativamente diferente e G2>G1. CONCLUSÃO: Hemorragia e hipotensão determinaram alterações na histologia renal. O aumento da concentração sangüínea de catecolaminas provavelmente determinou escores mais altos de alterações histológicas com o uso de S(+)cetamina.

Remifentanil, Isoflurane, and Preconditioning Attenuate Renal Ischemia/Reperfusion Injury in Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caffeic Acid Phenethyl Ester Effects in the Kidney During Ischemia and Reperfusion in Rats Anesthetized with Isoflurane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Erythropoietin Attenuates Apoptosis After Ischemia-Reperfusion-Induced Renal Injury in Transiently Hyperglycemic Wister Rats

Background. Hyperglycemia is associated with a decreased tolerance to ischemia and an increased severity of renal ischemia reperfusion (I/R) injury. It has been suggested that erythropoietin (EPO) attenuates this effect in normoglycemic animals. This study sought to examine the effects of EPO on treatment renal I/R injury (IRI) in transiently hyperglycemic rats.Material and Methods. Twenty-eight male Wister rats anesthetized with isoflurane received glucose (2.5 g.kg(-1) intraperitoneally) before right nephrectomy. They were randomly assigned to four groups: sham operation (S); IRI (ISO); IRI+EPO, (600 UI kg(-1) low-dose EPO [EL]); and IRI+EPO 5000 UI kg(-1) (high-dose EPO [EH]). IRI was induced by a 25-minute period of left renal ischemia followed by reperfusion for 24 hours. Serum Creatinine and glucose levels were measure at baseline (M1), immediately after the ischemic period (M2), and at 24 hours after reperfusion (M3). After sacrificing the animals, left kidney specimens were submitted for histological analysis including flow cytometry to estimate tubular necrosis and the percentages of apoptotic, dead or intact cells.Results. Scr in the ISO group was significantly higher at M3 than among the other groups. Percentages of early apoptotic cells in ISO group were significantly higher than the other groups. Percentages of late apoptotic cells in S and ISO groups were significantly greater than EL and EH groups. However, no significant intergroup differences were observed regarding the incidence of tubular necrosis.Conclusions. Our results suggested that, although not preventing the occurrence of tubular necrosis, EPO attenuated apoptosis and glomerular functional impairment among transiently hyperglycemic rats undergoing an ischemia/reperfusion insult.

Effects of pancreas transplantation on oxidative stress in pulmonary tissue from alloxan-induced diabetic rats

Purpose. There is considerable evidence that cellular oxidative stress caused by hyperglycemia plays an important role in the genesis and evolution of chronic diabetic lesions. In this study, we determined the effectiveness of pancreas transplantation (PT) in preventing the imbalance caused by excessive production of reactive oxygen species over antioxidant defenses in lungs of rats rendered diabetic by alloxan injection.Methods. Sixty inbred male Lewis rats, weighing 250-280 g, were randomly assigned to 3 experimental groups: NC, 20 nondiabetic control rats; DC, 20 untreated diabetic control rats; and PT, 20 diabetic rats that received syngeneic PT from normal donor Lewis rats. Each group was further divided into 2 subgroups of 10 rats each which were killed after 4 and 12 weeks of follow-up. Plasma glucose, glycosylated hemoglobin, and insulin levels were determined in all rats. Lipid hydroperoxide (LPO) concentrations and enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were measured in the pulmonary tissue of all rats.Results. The DC rats showed elevated blood glucose and glycosylated hemoglobin levels, with insulin blood levels significantly lower than the NC rats (P < .001). They also showed significantly increased LPO concentrations in the lungs (P < .01) after 4 and 12 weeks of follow-up. In contrast, SOD, CAT, and GSH-Px antioxidant activities were significantly reduced in these periods (P < .01) 12 weeks after diabetes induction. Successful PT corrected all clinical and metabolic changes in the diabetic rats, with sustained normoglycemia throughout the study. Excessive lung LPO production and low SOD, CAT, and GSH-Px antioxidant activities were already back to normal 4 weeks after PT.Conclusion. PT can control oxidative stress in pulmonary tissue of diabetic rats. It may be the basis for preventing chronic diabetic lesions in lungs.