| Full text | |
| Author(s): Show less - |
Coimbra‚ NC
;
De Oliveira‚ R.
;
Freitas‚ RL
;
Ribeiro‚ SJ
;
Borelli‚ KG
;
Pacagnella‚ RC
;
Moreira‚ JE
;
Da Silva‚ LA
;
Melo‚ LL
;
Lunardi‚ LO
;
others
Total Authors: 11
|
| Document type: | Journal article |
| Source: | Experimental Neurology; v. 197, n. 1, p. 93-112, 2006. |
| Abstract | |
Deep layers of the superior colliculus, the dorsal periaqueductal gray matter and the interior colliculus are midbrain structures involved ill the generation of defensive behavior and fear-induced anti-nociception. Local injections of the GABA(A) antagonist bicuculline into these structures have been used to produce this defense reaction. Serotonin is thought to be the main neurotransmitter to modulate such defense reaction in mammals. This study is the first attempt to employ immunohistochemical techniques to locate serotonergic cells in the same midbrain sites from where defense reaction is evoked by chemical stimulation with bicuculline. The blockade of GABAA receptors in the neural substrates of the dorsal mesencephalon was followed by vigorous defensive reactions and increased nociceptive thresholds. Light microscopy immuocytochemistry with streptavidin method was used for the localization of the putative cells of defensive behavior with antibodies to serotonin in the rat's midbrain. Neurons positive to serotonin were found in the midbrain sites where defensive reactions were evoked by microinjection of bicuculline. Serotonin was localized to somata and pro injections of the neural networks of the mesencephalic tectum. Immunohistochemical studies showed that the sites in which neuronal perikarya positive to serotonin were identified in intermediate and deep layers of the superior colliculus, and in the dorsal and ventral columns of the periaqueductal gray matter are the same which were activated during the generation of defense behaviors, such as alertness, freezing, and escape reactions, induced by bicuculline. These findings support the contention that serotonin and GABAergic neurons may act in concert in the modulation of defense reaction in the midbrain tectum. Our neuroanatomical findings indicate a direct neural pathway connecting the dorsal midbrain and monoaminergic nuclei of the descending pain inhibitory system, with profuse synaptic terminals mainly in the pontine reticular formation, gigantocellularis nucleus, and nucleus raphe magnus. The midbrain tectum-gigantocellularis complex and midbrain tectum-nucleus raphe magnus neural pathways may provide all alternative output allowing the organization of the fear-induced anti-nociception by mesencephalic networks. (c) 2005 Elsevier Inc. All rights reserved. (AU) | |
| FAPESP's process: | 98/11187-2 - Neurobiology of fear and stress |
| Grantee: | Marcus Lira Brandão |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 02/03705-0 - Neurobiology of fear and stress |
| Grantee: | Marcus Lira Brandão |
| Support Opportunities: | Research Projects - Thematic Grants |