Rough-and-tumble play induces resilience to stress in rats.

Positive emotions have been shown to induce resilience to stress in humans, as well as increase cognitive abilities (learning, memory, and problem solving) and improve overall health. In rats, frequency modulated 50-kHz ultrasonic vocalizations (hedonic 50 kHz) reflect a positive affective state and are best elicited by rough-and-tumble play. A well-established rat chronic unpredictable stress paradigm was used to produce a robust and long-lasting decrease in positive affect, increase in negative affect, and learned helplessness in Sprague-Dawley rats. Rough-and-tumble play (3 min every 3 days) reversed stress-induced effects of chronic unpredictable stress in the Porsolt forced swim test, novelty-induced hypophagia, sucrose preference, and ultrasonic vocalization assays compared with a light touch control group. These data demonstrate that positive affect induces resilience to stress effects in rats, and that rough-and-tumble play can be used to explore the biological basis of resilience that may lead to the development of new therapeutics for stress-related disorders.