Dorsal raphe nucleus and locus coeruleus neural networks and the elaboration of the sweet-substance-induced antinociception.
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 microg/0.2 microL) 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.
Kishi
Renato
R
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.
Bongiovanni
Renata
R
de Nadai
Tales Rubens
TR
Freitas
Renato Leonardo
RL
de Oliveira
Ricardo
R
Ferreira
Célio Marcos Dos Reis
CM
Coimbra
Norberto Cysne
NC
D000284:Administration, Oral; D000700:Analgesics / Q000008:administration & dosage; D000818:Animals; D008125:Locus Coeruleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009415:Nerve Net / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology*; D011903:Raphe Nuclei / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013395:Sucrose / Q000008:administration & dosage*
D000700:Analgesics; D013395:Sucrose