The strain of spontaneously hypertensive rats (SHR) is considered a genetic model for the study of attention-deficit hyperactivity disorder (ADHD), as it displays hyperactivity, impulsivity and poorly sustained attention. Recently, we have shown the involvement of adenosinergic neuromodulation in the SHR's short-term and long-term memory impairments. In this study, we investigated the performance of male and female SHR in a modified version of the object-recognition task (using objects with different structural complexity) and compared them with Wistar rats, a widely used outbred rat strain for the investigation of learning processes. The suitability of the SHR strain to represent an animal model of ADHD, as far as mnemonic deficits are concerned, was pharmacologically validated by the administration of methylphenidate, the first-choice drug for the treatment of ADHD patients. The role of adenosine A1 and A2A receptors in object discrimination was investigated by the administration of caffeine (nonselective antagonist) or selective adenosine receptor antagonists. Wistar rats discriminated all the objects used (cube vs. pyramid; cube vs. T-shaped object), whereas SHR only discriminated the most structurally distinct pairs of objects (cube vs. pyramid). Pretraining administration of methylphenidate [2 mg/kg, intraperitoneal (i.p.)], caffeine (1-10 mg/kg, i.p.), the selective adenosine receptor antagonists DPCPX (8-cyclopenthyl-1,3-dipropylxanthine; A1 antagonist, 5 mg/kg, i.p.) and ZM241385 (A2A antagonist, 1.0 mg/kg, i.p.), or the association of ineffective doses of DPCPX (3 mg/kg) and ZM241385 (0.5 mg/kg), improved the performance of SHR in the object-recognition task. These findings show that the discriminative learning impairments of SHR can be attenuated by the blockade of either A1 or A2A adenosine receptors, suggesting that adenosinergic antagonists might represent potentially interesting drugs for the treatment of ADHD.
Mate (Ilex paraguariensis A. St.-Hil) is a native species of South America used to prepare traditional beverages. Recently a possible effect of its infusion on oxidative stress found in dyslipidemias has been reported. The main compounds related to these activities are phenolic compounds derived from chlorogenic acid. This study aimed to determine the anticholesteremic effect of the hydroethanolic extract (HEIP) and its n-butanolic fraction (n-BFIP), with standardized content of phenolic compounds derived from chlorogenic acid, in rats treated with high-fat diet (HFD). The contents of these compounds in the ethanol extract and n-butanol fraction were respectively two and three times higher than in traditional infusion with predominance of dicaffeoylquinic derivatives. The extracts were able to reduce serum triglycerides and cholesterol and decrease the atherogenic index in treated animals. These results support a potential effect of the mate extract in cardiovascular disease.
Although Vitex megapotamica (Spreng.) Moldenke is used in Brazilian folk medicine as hypolipidemic drug no study has been conducted to evaluate the effects of this species in an experimental model of atherosclerosis. So, the aim of this study was to evaluate the possible renoprotective activity of methanolic extract obtained from Vitex megapotamica (MEVM) using C57BL/6 LDLr-null mice submitted to high fat diet (HFD). MEVM was orally administered at doses of 30, 100, and 300 mg/kg, for three weeks, starting from the 2nd week of HFD. Systolic blood pressure (SBP) and diuretic activity were measured weekly. At the end of experiments the serum lipids, atherogenic index serum (AIS), oxidative stress, and markers of renal function were determined. HFD induced a significant increase in the systolic blood pressure, dyslipidemia, increase in AIS, and lipid peroxidation accompanied by an important reduction in renal function. Treatment with MEVM was able to prevent increase in SBP, total cholesterol, triglycerides, AIS, urea, and creatinine levels in LDLr-null mice. These effects were accompanied by a significant reduction in oxidative stress and renal injury. The data reported here support the potential of Vitex megapotamica as candidate to be an herbal medicine used in cardiovascular or renal diseases.
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