New Perspectives on beta-Adrenergic Mediation of Innate and Learned Fear Responses to Predator Odor

In the present study, we investigated the role of noradrenergic transmission in unconditioned and conditioned responses to predatory threats. First, we examined the effects of systemically injected beta-blockers on unconditioned and contextual conditioned response to cat odor. The centrally acting beta-blocker (propranolol) was able to impair unconditioned responses, as well as the acquisition of the contextual fear to cat odor; however, the peripherally acting (nadolol) was not effective. Next, we examined the neural substrate underlying the noradrenergic modulation of the defensive response to cat odor and focused on the dorsal premammillary nucleus (PMd), because it represents the hypothalamic site most responsive to predatory threats and, at the same time, presents a dense plexus of noradrenergic fibers. We were able to see that propranolol significantly reduced PMd-Fos expression in response to cat odor and that beta-adrenoceptor blockade in the PMd, before cat odor exposure, reduced defensive responses to the cat odor and to the cat odor-related environment. We have also shown that beta-adrenoceptor blockade in the PMd, before the exposure to cat odor-related context, impaired the contextual conditioned responses. Overall, the present results provide convincing evidence suggesting that central noradrenergic mediation is critical for the expression of unconditioned and contextual conditioned antipredatory responses. We have further shown that the PMd appears to be an important locus to mediate these beta-adrenoceptor effects.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CAPES Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundacao de Apoio a Pesquisa Cientifica e Tecnologica do Estado de Santa Catarina (FAPESC)

Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC)

FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[05/59286-4]

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CNPq Conselho Nacional de Desenvolvimento Cientifico e Tecnologico