Amygdala and Periaqueductal Gray Lesions Only Partially Attenuate Unconditional Defensive Responses in Rats Exposed to a Cat

Defensive responses to a cat were observed in rats given excitotoxic lesions of the central nucleus of the amygdala (ACe), dorsolateral periaqueductal gray (dlPAG), ventral periaqueductal gray (vPAG), or sham lesions. Rats were placed adjacent to a compartment containing a cat. Sham-lesioned rats avoided the area nearest the cat and preferred the area furthest away from the cat. They also exhibited numerous defensive responses including, climbing, escape from the apparatus, and freezing. Rats with lesions of the ACe reacted like the sham lesioned rats by preferring the area of the apparatus furthest from the cat, however they climbed and escaped significantly less than sham lesioned rats. Avoidance of the area adjacent to the cat was attenuated in rats with lesions of the vPAG. Climbing along the walls of the apparatus was also attenuated in rats with lesions of the vPAG. Escapes from the apparatus were not significantly reduced by lesions of the vPAG and dlPAG. Thus, ACe lesions attenuated climbing and eliminated escapes, but did not impair locomotion of the rat away from the cat.