| Texto completo | |
| Autor(es): |
Eichenberger‚ GCD
;
Ribeiro‚ SJ
;
Osaki‚ MY
;
Maruoka‚ RY
;
Resende‚ GCC
;
Castellan-Baldan‚ L.
;
CorrÍa‚ SAL
;
Da Silva‚ LA
;
Coimbra‚ NC
Número total de Autores: 9
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Neuropharmacology; v. 42, n. 1, p. 48-59, 2002. |
| Resumo | |
The effects of central administration of opioid antagonists on the aversive responses elicited by electrical (at the freezing and escape thresholds) or chemical stimulation (crossings. rearings. turnings and jumps, induced by microinjections of bicuculline) of the midbrain tectum were determined. Central microinjections of naloxone and naltrexone in the mesencephalic tectum caused a significant increase in the freezing and escape thresholds elicited by electrical midbrain tectum stimulation. Furthermore, both opioid antagonists caused a significant decrease in the mean incidence of aversive behavioral responses induced by microinjections of bicuculline in the deep layers of the superior colliculus (DLSC) and in dorsal aspects of the periaqueductal gray matter (DPAG), as compared with controls. These findings suggest an opioid modulation of the GABAergic inhibitory inputs controlling the aversive behavior elicited by midbrain tectum stimulation. In fact, immunohistochemical evidence suggests that the dorsal mesencephalon is rich in (beta-endorphin-containing neurons and fibers with varicosities. Iontophoretical microinjections of the neurotracer biodextran in the substantia nigra. pars reticulata (SNpr), show nigro-tectal pathways connecting SNpr with the same neural substrate of the DPAG rich in neuronal cells immunoreactive for opioid peptides. Labeled neurons of the DLSC and periaqueductal gray matter send inputs with varsicosities to ipsi- and contralateral DPAG and ipsilateral SNpr. These findings. in addition to the psychopharmacological evidence for the interaction between opioid and GABAergic mechanisms, offer a neuroanatomical basis of a possible presynaptic opioid inhibition of GABAergic nigro-tectal neurons modulating the fear in aversive structures of the cranial mesencephalon. in a short link. and maybe through a major neural circuit, also in GABA-containing perikarya of nigro-tectal neurons. (C) 2002 Elsevier Science Ltd. All rights reserved. (AU) | |
| Processo FAPESP: | 00/08953-7 - Estudo neuroanatomico e psicofarmacologico do duplo elo gabaergico estriado-nigro-tectal e de sua influencia sobre o comportamento de defesa eliciado por estimulacao do coliculo inferior. |
| Beneficiário: | Lissandra Castellan Baldan |
| Modalidade de apoio: | Bolsas no Brasil - Mestrado |
| Processo FAPESP: | 96/06946-6 - Estudo da neuroquímica de processos aversivos e antinoceptivos em estruturas encefálicas, utilizando microeletrodos na determinação de neurotransmissores in vitro e in vivo através de voltametria cíclica e de pulso diferencial |
| Beneficiário: | Luis Antonio da Silva |
| Modalidade de apoio: | Bolsas no Brasil - Jovens Pesquisadores |
| Processo FAPESP: | 98/11187-2 - Neurobiologia do medo e da ansiedade |
| Beneficiário: | Marcus Lira Brandão |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |