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The role of oxide nitric system of the dorsolateral periaqueductal gray in the emotional memory to predatory threats

Grant number: 11/03789-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): September 01, 2011
Effective date (End): August 31, 2013
Field of knowledge:Biological Sciences - Physiology
Principal Investigator:Sandra Regina Mota Ortiz
Grantee:Rodrigo de Andrade Rufino
Home Institution: Pró-Reitoria de Pós-Graduação, Pesquisa e Extensão. Universidade Cidade de São Paulo (UNICID). São Paulo , SP, Brazil

Abstract

The PAG is known to play an important role in a number of anti-predator related responses, such as the modulation of nociceptive sensory transmission, regulation of the cardiovascular system, vocalization, and organization of motor patterns in response to live predators. As originally noted by Hunsperger (1956), the PAG is a key site to organize defensive responses, where lesions result in passive animals that rarely, if ever, show defensive behavior. Of particular relevance, the dorsal PAG (dPAG) is the major target of the defensive behavioral control column in the medial hypothalamus, and the pattern of projection from the medial hypothalamic zone to the PAG largely overlaps the pattern of PAG activation in animals exposed to a predator, where Fos expression was mostly seen in the rostral two-thirds of the PAG in the dorsomedial and dorsolateral regions. Thus, the dPAG appears to play a critical role in the PAG for integration forebrain limbic information related to "psychological stressors", such as the presence of a natural predator. Recently, we suggested an additional rather integrative PAG function in influencing motivational behavioral responses, such as risk-assessment responses. We have found that animals exposed to the environment where a live cat had been previously encountered present pattern PAG activation similar to the one seen in response to the actual predator. The dPAG seems to be particularly responsive to both the actual predator and, to the predator-related context cues. In the present work, we investigated how pharmacological blocked of the dPAG, after cat exposure, interferes with the conditioned antipredatory defensive behavior. The results indicated that muscimol inactivation of the dPAG after 10 min of cat exposure completely blocks the predatory contextual conditioning. Therefore, it is reasonable to believe that under natural circumstances sustained dPAG activation is seemingly required to support aversive learning, working through a path involving a feedback loop to the hypothalamic defensive system and its allied thalamo-cortical loops. (AU)