Influence of the anterior cingulate cortex and involvement of hypothalamic NMDA and AMPA/kainite glutamatergic receptorsin the organization of the defensive behaviorand innate fear-induced antinociception elaborated by posterior hypothalamus
Eletrical and chemical stimulation of some mesencefalic strucutres, as dorsal periaqueductal grey matter, the deep layers of the superior colliculus and central nuclei of inferior colloculus elicite explosive defensive response, associated with fear and similar to those characterized to panic disorder in humans. However, when the stimulation are done into medial hypothalamus, the defensive response arecharacterized by a well elaborated escape. There are some evidence that the cingulate gyrus send projections to posterior hypothalamic nucleus, which the stimulation also is followed by escape and fear-induced antinociception. Medial and posterior hypothalamus, diencephalic strucutres related to envolviment with modulation of sympathetic division of the autonomic nervous system, are modulated by a tonic GABAergics pathways, which is critically recruited during the elaborations of defense responses. There are only a few works about mechanisms that underlie modulation of pain perception mediated cortical areas such as the anterior cingulate cortex (ACC). The aim of the presente work is to investigate the connections between the anterior cingulate cortex with posterior hypothalamic nuclei, and with the nuclei of the system of inhibition of endogenous pain such locus coeruleus and dorsal raphe nuclei, through a neuroanatomic study with microinjections of an iontophoretic neurotraçador of anterograde and retrograde, a biodextrana marked with Texas Red in the ACC, followed by Immunohistochemical methods for the detection and the type glutamate receptors NMDA e AMPA/Kainate into posterior hypothalamus. It will be also study the effect os neural inativation of cortical afferents described previously, by microinjection of lidocaina at 2% into-ACC, in order to investigate if these structures play some role modulating the fear-induced antinociception induced by posterior hypothalamus chemistry stiulation. Independents groups will be study in order to analise the effect os the pre-treatment into-postior hypothalamus with microinjections of LY235959, a NMDA receptor glutamatergic selective antagonist or NBQX, a AMPA e kainate receptor glutamatergic competitive antagonist, to evaluate the involviment of posteiror hypothalamus glutamatergic neurotransmitter during the organization of fear-induced antinociception induced by defensive reactions after bicuculline microinjections (40 ng / 200 nL), a GABAA receptor antagonist into-posteiror hypothalamus.
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