Prolonged exposure to conspecific and predator odors reduces fear reactions to these odors during subsequent prod-shock tests

Abstract

In Experiment 1, four groups ofmale rats were given a session as an intruder in either aggressive (i.e., alpha) or nonaggressive colonies of conspecifics and later received either a 2-h exposure to the odors of the alpha colonies or an exposure-control session with the odors of a nonalpha colony. Two additional groups of rats that had been attacked and defeated by alpha residents were later given a 12-h exposure session with alpha-colony odors or nonalpha-control odors. Twentyfour h after the colony-intruder session, all subjects were given a single 6.5-mA shock from a prod with alpha-colony odors present in the bedding ofthe test chamber. Attacked rats that had been given exposure-control sessions showed significantly less prod burying and greater freezing than nondefeated subjects. This implies that the alpha-colony odors elicited conditioned fear. In contrast, the attacked subjects that had been given apretest exposure session with alpha-colony odors showed significantly more prod burying and significantly less freezing. This suggests that the alpha-odor exposure resulted in the extinction of fear to these odors. Furthermore, the 12-h exposure to alpha-colony odors was found to be more effective in reducing fear-mediated responses than was the 2-h exposure. In Experiment 2, three groups of rats were exposed to a cat while they were in a protective cage; later they were given a 12-h exposure session with cat odors, a 12-h exposure-control session with no cat odors, or no exposure treatment. Compared with the two control groups, the subjects that were exposed to cat odors showed less freezing during subsequent prod-shock tests in the presence of cat odors, but they did not show prod burying. The reported changes in fear-mediated reactions to the odors of conspecifics and a predator are discussed in terms of both associative and nonassociative processes.Over the past several years, considerable research has examined the influence that both laboratory and natural stressors, and their relatedodors, have on subsequent fearmediated responses producedby the use of the prod-shock procedure (see Williams, 1987aWilliams, , 1989, for reviews). This procedure, which has been extensively studied by Pinel and his colleagues (e.g., Pinel & Treit, 1978, 1981, consists of administering a single electric shock from a prod that is mounted on the wall of achamber with movable beddingmaterialon the floor. Whentested withthis procedure, rats typically show abrief freezing reaction foIlowing the prod shock, and then they bury the prod with the bedding material. AlthoughPinel has interpretedthis type of prod burying to be a conditioned defensive response (Pinel & Treit, 1978, 1981Treit, 1985), others have claimed that it is an example of shock-elicited spraying or burrowing (Fanselow, Sigmundi, & Williams,

Ventilatory frequency as a measure of the response of tammar wallabies (Macropus eugenii) to the odour of potential predators

“…This exploratory behaviour is similar to that observed for other mammals exposed to predator olfactory stimuli (Caine and Weldon 1989;McGregor et al 2002;. For example, rodents displayed similar odour assessment when presented with the scent of cat (Blanchard and Blanchard 1989;Williams et al 1990) The initial exploratory increase in f R by tammar wallabies generally decreased in the second minute. This is consistent with the hypothesis the initial reaction was investigative in nature.…”

Effects of Predator-Induced Stress and Age on Working Memory in Rats

“…More pertinent to the present study, it has been demonstrated that exposing rats to the odors of cats increased plasma levels of corticosterone (File et aI., 1993) and to the actual presence of a cat produced defensive fear responses and opioid-mediated analgesia (Lester & Fanselow, 1985;Williams & Barber, 1990;Williams & Groux, 1993;Williams, Rogers, et aL, 1990;Williams & Scott, 1989). As noted previously, opioid antagonists have been found to enhance memory Gallagher, Bostock, & King, 1985) and opioid agonists, such as morphine, to suppress memory (Spain & Newman, 1991).…”

“…Williams and his colleagues have shown that when rats are attacked and defeated by a dominant, or alpha male rat, learning and motivational deficits ensue that are accompanied by opioid-mediated analgesia (e.g., Hotsenpiller & Williams, 1996;Williams, 1989;Williams, Worland, & Smith, 1990). Of particular relevance to the current study, rats that have been exposed to a cat and/or cat odors, as a predator stressor, also display defensive fear responses and opioidmediated analgesia (Lester & Fanselow, 1985;Williams & Barber, 1990;Williams & Groux, 1993;Williams, Rogers, & Adler, 1990;Williams & Scott, 1989). In addition, File, Zangrossi, Sanders, and Mabbutt (1993) reported that when rats were exposed to the odors of cats intermittently for five daily sessions, they showed a significant increase in blood-plasma levels of corticosterone by the 3rd day.…”

Effects of prior agonistic experience on risk assessment and approach behavior evoked by familiar or unfamiliar conspecific odors

“…Previous research with rats [Williams et al, 1990a;Williams and Scott, 19891 led us to expect clear differences in responsiveness to these odors. Rearing, grooming, and digging behaviors were also recorded to provide some index of appetitive behaviors.…”