LEARNING AND MEMORYDefensive freezing evoked by electrical stimulation of the periaqueductal gray: comparison between dorsolateral and ventrolateral regionsVianna, Daniel M. L.1; Graeff, Frederico G.2; Brandão, Marcus L.1; Landeira-Fernandez, Jesus3,4, CAAuthor Information 1Laboratório de Psicobiologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, and 2Departamento de Neurologia, Psiquiatria e Psicologia Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo (USP), 14049-900, Ribeirão Preto, SP; 3Laboratório de Psicologia Comparada, Universidade Estácio de Sá, Rio de Janeiro, Brazil; 4Laboratório de Neurociências e Comportamento, Departamento de Psicologia, Pontifícia Universidade Católica do Rio de Janeiro, PUC-Rio, Rua Marquês de São Vicente, 225, Rio de Janeiro, RJ 22453-900 CA,3Corresponding Author and Address Received 28 September 2001; accepted 24 October 2001 Neuroreport: December 21st, 2001 - Volume 12 - Issue 18 - p 4109-4112 Buy SDC Abstract Previous reports indicated that ventrolateral periaqueductal gray (vlPAG) plays a role in the expression of freezing behavior whereas dorsolateral periaqueductal gray (dlPAG) is involved on both freezing and active forms of defensive behaviors. In order to evaluate the role of each of these areas in the occurrence of defensive reactions, rats were electrically stimulated either in the dlPAG or vlPAG with different stimulus frequencies. Stepwise increases in the electrical stimulation of both dlPAG or vlPAG induced initially freezing and then a jumping response. Freezing induced by vlPAG stimulation had a tendency to disappear when the stimulation was turned off whereas freezing induced by dlPAG stimulation remained high in the absence of the stimulation. These results suggest that dlPAG and vlPAG are involved on defensive freezing probably through different neural circuitries. © 2001 Lippincott Williams & Wilkins, Inc.