Navegando por Palavras-chave "PAG"

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    Methimazole-induced hypothyroidism inhibits the panic-like behaviors produced by electrical stimulation of dorsal periaqueductal gray matter of rats
    (Elsevier B.V., 2010-06-01) Siqueira, Carla Coelho; Rossoni, Renzo Roldi; Carleti Pereira Tiengo, Ana Neide; Tufik, Sergio [UNIFESP]; Schenberg, Luiz Carlos; Univ Fed Espirito Santo; Universidade Federal de São Paulo (UNIFESP)
    Conflicting clinical data on the relationship of panic disorder and thyroid diseases illustrate the need for a simpler approach using animal models. Defensive behaviors evoked by electrical or chemical stimulation of dorsal periaqueductal gray matter (DPAG) have been proposed as a model of panic attack. Therefore, the present study examined the effects of the anti-thyroid agent methimazole (MTZ) either on the panic-like behaviors induced by electrical stimulation of DPAG or the anxiety-like behaviors of rats exposed to the elevated plus-maze (EPM). Male Wistar rats bearing electrodes in the DPAG were stimulated with stepwise increased currents. Rats which displayed galloping at intensities below 60 mu A were retested following 5- and 10-day treatments with MTZ (0.6 mg/kg/day, i.p.) or 10- and 15-day washout periods. MTZ effects on EPM performance were assessed in separate groups. MTZ-treated groups were compared to saline-treated controls. in other experiments, rats were similarly treated with MTZ and the blood was collected for hormone assays. the 10-day treatment with MU produced marked increases in the thresholds of exophthalmus (65%), immobility (75%), trotting (63%), galloping (56%), jumping (47%), defecation (114%) and micturition (85%). Effects outlasted the drug discontinuation. in contrast, MU had variable effects in the EPM, significantly increasing the open-arm exploration in 5-day treated and 10-day washout groups. Biochemical data revealed a small but significant decrease (13%) in free thyroxine in MTZ-treated groups. Although not significant, thyrotrophin levels showed a 111% increase following the 10-day treatment with MU. Selective attenuation by MU of DPAG-evoked defensive behaviors supports attenuation of panic attacks in hypothyroidism. (c) 2009 Elsevier B.V. All rights reserved.
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    Organization of single components of defensive behaviors within distinct columns of periaqueductal gray matter of the rat: Role of N-methyl-D-aspartic acid glutamate receptors
    (Elsevier B.V., 2004-01-01) Bittencourt, A. S.; Carobrez, A. P.; Zamprogno, L. P.; Tufik, S.; Schenberg, L. C.; Univ Fed Espirito Santo; Universidade Federal de Santa Catarina (UFSC); Universidade Federal de São Paulo (UNIFESP)
    The periaqueductal gray matter (PAG) is functionally organized in longitudinal columns arranged along the aqueduct. Stimulation of lateral and dorsal columns produces a complex set of unconditioned behaviors named the 'defense reaction.' Overt responses in rats comprise a tense immobile display, fully opened eyes (herein named exophthalmus), trotting, galloping, jumping, micturition and defecation. Besides, the PAG is rich in glutamate and respective receptors, including the N-methyl-D-aspartic acid (NMDA) type. Therefore, the present study employed regression analysis to map out electrically and NMDA-induced single components of defensive behaviors produced by stepwise increasing stimulation of PAG. Data confirmed the defensive nature of PAG-evoked responses. Neither the appetitive, nor offensive, mouse-killing or male reproductive behaviors were produced by stimulation of PAG in presence of appropriate targets. Threshold and dose-response logistic analyses largely corroborated the columnar organization of PAG-evoked responses. Thus, whereas the defecation was restricted to PAG lateral column, exophthalmus, micturition and somatic defensive responses were similarly organized in dorsolateral and lateral, but not in the ventrolateral column. Moreover, thresholds of dorsolateral and lateral repertoires were strictly hierarchical, with exophthalmus, immobility, trotting, galloping and jumping appearing in this very order. However, the defensive responses of PAG dorsolateral column required NMDA doses significantly lower than those of lateral PAG. Accordingly, NMDA receptors within the dorsolateral PAG are likely to play a major role in the initiation of PAG-evoked defensive responses. in contrast, the present data do not support the organization of unconditioned defensive behaviors in ventrolateral PAG. the neuroanatomical substrate of each response and the role of PAG and NMDA receptors are discussed in relation to the present data. Further, this is the first report on PAG columnar organization of single components of defensive behaviors. (C) 2004 IBRO. Published by Elsevier B.V. All rights reserved.