Social play behavior, ultrasonic vocalizations and their modulation by morphine and amphetamine in Wistar and Sprague-Dawley rats
Social play behavior is the most characteristic social behavior in young mammals. It is highly rewarding and crucial for proper neurobehavioral development. Despite the importance of genetic factors in normal and pathological social behaviors, little information is available about strain influences on social play.
Objective and methods
The aim of this study was to investigate differences in social play behavior, 50-kHz ultrasonic vocalizations (USVs) and their modulation by acute morphine and amphetamine administration in two rat strains widely used in behavioral pharmacology studies, i.e., Wistar and Sprague–Dawley rats.
Sprague–Dawley rats showed higher levels of social play than Wistar rats. In both strains, no correlation was found between the performance of social behaviors and the emission of 50-kHz USVs. In Wistar and Sprague–Dawley rats, morphine increased and amphetamine decreased social play. The effects of morphine, however, were more pronounced in Wistar than Sprague–Dawley animals. In both strains, morphine did not affect USV emission, while amphetamine increased it during cage exploration. In Sprague–Dawley rats only, amphetamine decreased USVs during social interaction.
Wistar and Sprague–Dawley rats differ in their absolute levels of social play behavior and 50-kHz USVs, and quantitative differences exist in their response to pharmacological manipulations of social play. The emission of 50-kHz USVs and the behavioral parameters thought to reflect rewarding social interactions in adolescent rats are dissociable.
KeywordsSocial behavior USV Adolescence Opioids Psychostimulants
This study was supported by Veni grant 91611052 (Nederlandse Organisatie voor Wetenschappelijk Onderzoek, V.T.), Marie Curie Career Reintegration Grant PCIG09-GA-2011-293589 (Seventh Framework Programme People, V.T.), and Futuro in Ricerca 2010 (Italian Ministry for University and Scientific Research, V.T., P.C.). We thank Andrea Peloso, Lidia Montebello, and Alessandro Pasquale (Master students, Department of Physiology and Pharmacology, Sapienza, University of Rome) for their technical help.
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