Effects of auditory stress on grooming dominance in the rat

Abstract

Two experiments examined the effects of high-intensity white noise on the subsequent monopolization of mutual grooming by dominant members of male rat pairs. Only in cases where dominants were subjected to acoustic stress in the absence of another rat did they manifest a reduction in subsequent grooming behavior. Stressed in the company of either their own submissive partners or randomly selected rats, dominants continued to monopolize mutual grooming activity. The data emphasized the relevance of the social context in which stress is administered for the consequent social reactivity of the laboratory rat.It has been shown by Spigel, Trivett, and Fraser (1972) that the monopolization of mutual grooming by dominant members of male rat pairs was a more stable and consistent index of social ascendancy than competition for water, the latter being more subject to variation related to the motivational state of the animal. It has also been observed that shock-induced fear does not necessarily lead to greater affiliative behavior in the laboratory rat, despite evidence that fewer signs of fear are present when animals are together than when alone (Latane, Friedman, & Thomas, 1972). In addition, a relationship has been demonstrated (Williams & Eichelman, 1971) between differential physiological responses, e.g., blood pressure change, in response to shock and the social setting in which the shock is administered.The possibility that stress is reduced by manipulating social variables is suggested by the work of Morrison and Hill (1967), who found socially facilitated fear reduction in an approach-avoidance situation. In order to examine the wider implications of the relationship between social conditions and stress, the current experiments sought to determine whether established dominant-submissive relationships in male rat pairs, as measured by mutual grooming, would .be affected by auditory stress under differential social settings. EXPERIMENT IThe question raised in the first experiment was whether any differences would emerge in dominance, as manifested by grooming behavior, following periods of high-intensity noise administered with and without the presence of other rats. The aversive nature of high-intensity noise has been documented by Pinel, MethodSubjects. Forty-eight male Wistar rats ordered at 90 days of age were employed. All Ss were housed individually on reversed light cycles from arrival to the conclusion of the study, food and water remaining available at all times in home cages.Apparatus. The grooming test chamber used was a 24 x 24 in. box, 18 in. high, painted gray. An lAC acoustic chamber, 23% x 31% x 23 in., was modified with a speaker fed from a Sony tape recorder containing prerecorded white noise bursts of varying durations from 3 to 15 sec. The l Omin noise program was arranged so that the actual bursts of sound totaled 5 min but were delivered in a semirandom fashion over the l O-min period at 122 dB.Procedure. Following 1 week of laboratory habituation, rats were rank ordered by body weight, pai...

Witnessing traumatic events and post-traumatic stress disorder: Insights from an animal model

“…Several studies have reported that PTSD-like behaviors last at least 3–4 weeks after experiencing traumatic events [1, 23] and that olfactory or auditory stress alone cause cognitive and behavioral impairments in animals [18, 19]. Limited information is however available regarding the witnessing aspects of trauma and persistence of PTSD-like behaviors [21].…”