Dorsal raphe nucleus and locus coeruleus neural networks and the elaboration of the sweet-substance-induced antinociception |
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Authors: | Renato Kishi Renata BongiovanniTales Rubens de Nadai Renato Leonardo FreitasRicardo de Oliveira Célio Marcos dos Reis FerreiraNorberto Cysne Coimbra |
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Institution: | Laboratório de Neuroanatomia e Neuropsicobiologia, Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP), Avenida dos Bandeirantes, 3900, Ribeirão Preto (SP) 14049-900, Brasil |
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Abstract: | In order to investigate the effects of monoaminergic neurons of the dorsal raphe nucleus (DRN) and locus coeruleus (LC) on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180–200 g received sucrose solution (250 g/L) for 7–14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of ibotenic acid (1.0 μg/0.2 μL) in the DRN or in the LC. The tail withdrawal latencies of the rats in the tail-flick test were measured immediately before and 7 days after this treatment. The neurochemical lesion of locus coeruleus, but not of DRN neural networks with ibotenic acid, after the chronic intake of sweetened solution, decreased the sweet-substance-induced antinociception. These results indicate the involvement of noradrenaline-containing neurons of the LC in the sucrose-induced antinociception. We also consider the possibility of DRN serotonergic neurons exerting some inhibitory effect on the LC neural networks involved with the elaboration of the sweet-substance-induced antinociception. |
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Keywords: | Sweet-substance-induced analgesia Tail-flick test Dorsal raphe nucleus Locus coeruleus Pain endogenous inhibitory system |
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