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Background: Angiotensin II, is critical in regulating the sympathetic and neuroendocrine systems through angiotensin II type 1 receptors (AT 1 -R). Angiotensin II intracerebral administration increases water and sodium intake, as well as renal sodium excretion. Previously, our group has shown that AT 1 -R is involved in behavioral and neurochemical sensitization induced by amphetamine. We aimed to assess the physiological output, behavioral, and neurochemical responses to intracerebral angiotensin II administration, via the AT 1 -R, twenty-one days after amphetamine administration., Material and Methods: Male Wistar rats received daily vehicle or AT 1 -R antagonist (oral) for 10 days, and amphetamine or saline intraperitoneal (i.p.) from day 6 to 10. On day 25 they were implanted with an intracerebral cannula. On day 32, the animals received intracerebral angiotensin II. First group: the animals were tested in a free choice paradigm for 2% NaCl and water intake, and sacrificed for neuronal activity assessment via c-Fos immunohistochemistry. Second group: urine samples were collected for electrolyte determination. Third group: the animals were tested in the plus maze or the hole board for anxiety and working memory evaluation, respectively, and sacrificed for c-Fos immunohistochemistry., Results: Amphetamine exposure blunted the increase in sodium intake ( p = 0.0022), and potentiated the natriuretic ( p = 0.0043) and kaliuretic effect ( p = 0.0002) induced by angiotensin II. Moreover, amphetamine exposure prevented the expression of the anxiogenic effect (drug effect p < 0.0001) and the memory deficit ( p = 0.1314) induced by cerebral angiotensin II administration. Amph decreased c-Fos immunoreactivity in nucleus tractus solitarii (NTS) p = 0.0037; paraventricular nucleus (PVN) p = 0.0047; Central amygdala (CeA) p = 0.0008; Basolateral amygdala (BLA) p = 0.0018; increased in hippocampus region CA1 p = 0.0043; CA3 p = 0.026; and dentate gyrus (DG) p = 0.0057. The blockade of AT 1 -R prevented these alterations (sodium intake p = 0.0421 natriuresis p = 0.019; kaliuresis p = 0.196; working memory ( p < 0.0001); but no the anxiogenic response to angiotensin II (drug effect p < 0.0001); as well as the c-Fos changes (NTS p = 0.0052; PVN p = 0.029; CeA p = 0.0002; BLA p = 0.0021; CA1 p = 0.0026; CA3 p = 0.022; and DG p = 0.0016)., Conclusion: Most of the long-lasting AT 1 -R altered responses to brain angiotensin II administration induced by repeated amphetamine exposure could be prevented by AT 1 -R blockade.

Amphetamine (AMPH) exposure induces behavioural and neurochemical sensitization observed in rodents as hyperlocomotion and increased dopamine release in response to a subsequent dose. Brain Angiotensin II modulates dopaminergic neurotransmission through its AT 1 receptors (AT 1 -R), positively regulating striatal dopamine synthesis and release. This work aims to evaluate the AT 1 -R role in the development and maintenance of AMPH-induced sensitization. Also, the AT 1 -R involvement in striatal dopamine reuptake was analysed. The sensitization protocol consisted of daily AMPH administration for 5 days and tested 21 days after withdrawal. An AT 1 -R antagonist, candesartan, was administered before or after AMPH exposure to evaluate the participation of AT 1 -R in the development and maintenance of sensitization, respectively. Sensitization was evaluated by locomotor activity and c-Fos immunostaining. Changes in dopamine reuptake kinetics were evaluated 1 day after AT 1 -R blockade withdrawal treatment, with or without the addition of AMPH in vitro. The social interaction test was performed as another behavioural output. Repeated AMPH exposure induced behavioural and neurochemical sensitization, which was prevented and reversed by candesartan. The AT 1 -R blockade increased the dopamine reuptake kinetics. Neither the AMPH administration nor the AT 1 -R blockade altered the performance of social interaction. Our results highlight the AT 1 -R's crucial role in AMPH sensitization. The enhancement of dopamine reuptake kinetics induced by the AT 1 -R blockade might attenuate the neuroadaptive changes that lead to AMPH sensitization and its self-perpetuation. Therefore, AT 1 -R is a prominent candidate as a target for pharmacological treatment of pathologies related to dopamine imbalance, including drug addiction and schizophrenia., (© 2024 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Amphetamine-induced neuroadaptations involve vascular damage, neuroinflammation, a hypo-functioning prefrontal cortex (PFC), and cognitive alterations. Brain angiotensin II, through angiotensin type 1 receptor (AT 1 -R), mediates oxidative/inflammatory responses, promoting endothelial dysfunction, neuronal oxidative damage and glial reactivity. The present work aims to unmask the role of AT 1 -R in the development of amphetamine-induced changes over glial and vascular components within PFC and hippocampus. Attention deficit was evaluated as a behavioral neuroadaptation induced by amphetamine. Brain microvessels were isolated to further evaluate vascular alterations after amphetamine exposure. Male Wistar rats were administered with AT 1 -R antagonist, candesartan, followed by repeated amphetamine. After one week drug-off period, animals received a saline or amphetamine challenge and were evaluated in behavioral tests. Afterward, their brains were processed for cresyl violet staining, CD11b (microglia marker), GFAP (astrocyte marker) or von Willebrand factor (vascular marker) immunohistochemistry, and oxidative/cellular stress determinations in brain microvessels. Statistical analysis was performed by using factorial ANOVA followed by Bonferroni or Tukey tests. Repeated amphetamine administration increased astroglial and microglial markers immunoreactivity, increased apoptotic cells, and promoted vascular network rearrangement at the PFC concomitantly with an attention deficit. Although the amphetamine challenge improved the attentional performance, it triggers detrimental effects probably because of the exacerbated malondialdehyde levels and increased heat shock protein 70 expression in microvessels. All observed amphetamine-induced alterations were prevented by the AT 1 -R blockade. Our results support the AT 1 -R involvement in the development of oxidative/inflammatory conditions triggered by amphetamine exposure, affecting cortical areas and increasing vascular susceptibility to future challenges., (© 2019 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

The use of psychostimulants, such as amphetamine (Amph), is associated with inflammatory processes, involving glia and vasculature alterations. Brain Angiotensin II (Ang II), through AT 1 -receptors (AT 1 -R), modulates neurotransmission and plays a crucial role in inflammatory responses in brain vasculature and glia. Our aim for the present work was to evaluate the role of AT 1 -R in long-term alterations induced by repeated exposure to Amph. Astrocyte reactivity, neuronal survival and brain microvascular network were analysed at the somatosensory cortex. Thermal nociception was evaluated as a physiological outcome of this brain area. Male Wistar rats (250-320 g) were administered with AT 1 -R antagonist Candesartan/vehicle (3 mg/kg p.o., days 1-5) and Amph/saline (2.5 mg/kg i.p., days 6-10). The four experimental groups were: Veh-Sal, CV-Sal, Veh-Amph, CV-Amph. On day 17, the animals were sacrificed and their brains were processed for Nissl staining and immunohistochemistry against glial fibrillary acidic protein (GFAP) and von Willebrand factor. In another group of animals, thermal nociception was evaluated using hot plate test, in the four experimental groups, on day 17. Data were analysed with two-way anova followed by Bonferroni test. Our results indicate that Amph exposure induces an increase in: neuronal apoptosis, astrocyte reactivity and microvascular network, evaluated as an augmented occupied area by vessels, branching points and their tortuosity. Moreover, Amph exposure decreased the thermal nociception threshold. Pretreatment with the AT 1 -R blocker prevented the described alterations induced by this psychostimulant. The decreased thermal nociception and the structural changes in somatosensory cortex could be considered as extended neuroadaptative responses to Amph, involving AT 1 -R activation., (© 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

A single exposure to amphetamine induces neurochemical sensitization in striatal areas. The neuropeptide angiotensin II, through AT 1 receptors (AT 1 -R) activation, is involved in these responses. However, amphetamine-induced alterations can be extended to extra-striatal areas involved in blood pressure control and their physiological outcomes. Our aim for the present study was to analyze the possible role for AT 1 -R in these events using a two-injection protocol and to further characterize the proposed AT 1 -R antagonism protocol. Central effect of orally administered AT 1 -R blocker (Candesartan, 3mg/kg p.o.×5days) in male Wistar rats was analyzed by spontaneous activity of neurons within locus coeruleus. In another group of animals pretreated with the AT 1 -R blocker or vehicle, sensitization was achieved by a single administration of amphetamine (5mg/kg i.p. - day 6) followed by a 3-week period off drug. On day 27, after receiving an amphetamine challenge (0.5mg/kg i.p.), we evaluated: (1) the sensitized c-Fos expression in locus coeruleus (LC), nucleus of the solitary tract (NTS), caudal ventrolateral medulla (A1) and central amygdala (CeAmy); and (2) the blood pressure response. AT 1 -R blockade decreased LC neurons' spontaneous firing rate. Moreover, sensitized c-Fos immunoreactivity in TH+neurons was found in LC and NTS; and both responses were blunted by the AT 1 -R blocker pretreatment. Meanwhile, no differences were found neither in CeAmy nor A1. Sensitized blood pressure response was observed as sustained changes in mean arterial pressure and was effectively prevented by AT 1 -R blockade. Our results extend AT 1 -R role in amphetamine-induced sensitization over noradrenergic nuclei and their cardiovascular output., (Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.)

Unlabelled: Previous results from our laboratory showed that angiotensin II AT1 receptors (AT1-R) are involved in the neuroadaptative changes induced by amphetamine. The aim of the present work was to study functional and neurochemical responses to angiotensin II (ANG II) mediated by AT1-R activation in animals previously exposed to amphetamine. For this purpose male Wistar rats (250-320 g) were treated with amphetamine (2.5mg/kg/day intraperitoneal) or saline for 5 days and implanted with intracerebroventricular (i.c.v.) cannulae. Seven days after the last amphetamine administration the animals received ANG II (400 pmol) i.c.v. One group was tested in a free choice paradigm for sodium (2% NaCl) and water intake and sacrificed for Fos immunoreactivity (Fos-IR) determinations. In a second group of rats, urine and plasma samples were collected for electrolytes and plasma renin activity determination and then they were sacrificed for Fos-IR determination in Oxytocinergic neurons (Fos-OT-IR)., Results: Repeated amphetamine exposure (a) prevented the increase in sodium intake and Fos-IR cells in caudate-putamen and accumbens nucleus induced by ANG II i.c.v. (b) potentiated urinary sodium excretion and Fos-OT-IR in hypothalamus and (c) increased the inhibitory response in plasma renin activity, in response to ANG II i.c.v. Our results indicate a possible functional desensitisation of AT1-R in response to ANG II, induced by repeated amphetamine exposure. This functional AT1-R desensitisation allows to unmask the effects of ANG II i.c.v. mediated by oxytocin. We conclude that the long lasting changes in brain AT1-R functionality should be considered among the psychostimulant-induced neuroadaptations., (Published by Elsevier Ltd.)

A single or repeated exposure to psychostimulants induces long-lasting neuroadaptative changes. Different neurotransmitter systems are involved in these responses including the neuropeptide angiotensin II. Our study tested the hypothesis that the neuroadaptative changes induced by amphetamine produce alterations in brain RAS components that are involved in the expression of the locomotor sensitization to the psychostimulant drug. Wistar male rats, pretreated with amphetamine were used 7 or 21 days later to study AT1 receptors by immunohistochemistry and western blot and also angiotensinogen mRNA and protein in caudate putamen and nucleus accumbens. A second group of animals was used to explore the possible role of Ang II AT1 receptors in the expression of behavioral sensitization. In these animals treated in the same way, bearing intra-cerebral cannula, the locomotor activity was tested 21 days later, after an amphetamine challenge injection and the animals received an AT1 blocker, losartan, or saline 5min before the amphetamine challenge. An increase of AT1 receptor density induced by amphetamine was found in both studied areas and a decrease in angiotensinogen mRNA and protein only in CPu at 21 days after treatment; meanwhile, no changes were established in NAcc. Finally, the increased locomotor activity induced by amphetamine challenge was blunted by losartan administration in CPu. No differences were detected in the behavioral sensitization when the AT1 blocker was injected in NAcc. Our results support the hypothesis of a key role of brain RAS in the neuroadaptative changes induced by amphetamine., (Published by Elsevier B.V.)