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.