Ultraschallkommunikation bei Ratten: Soziale Isolation als Risikofaktor für neuropsychiatrische Erkrankungen mit defizitärem Sozialverhalten im Tiermodell

Rats are highly social animals and communication is an important component in the social behavior repertoire. They produce and perceive calls in the ultrasonic range (so called ultrasonic vocalizations, USV) which serve distinct communicative functions, as situation-dependent affective signals. In juvenile and adult rats, two different call types can be differentiated. Low-frequency 22-kHz USV typically occur in aversive situations, such as social defeat, while high-frequency 50-kHz USV can be observed in appetitive situations such as social play behavior in juvenile or mating behavior in adult rats. Both call types have distinct communicative functions and elicit call type-specific behavior in the recipient. 22-kHz USV serve as an alarm function and induce freezing behavior in the recipient. In contrast, 50-kHz USV serve a pro-social communicative function. Male 50-kHz USV play an important role to establish social proximity and are probably also involved in the regulation of sexual behavior (Study I:. Willadsen et al, 2014). In the non-sexual context, there is strong evidence that 50-kHz USV serve as social contact calls. Studies that applied the established playback paradigm so far were reviewed and it was demonstrated that playback of 50-kHz USV consistently led to social approach behavior in the recipient, indicating that pro-social ultrasonic communication can be studied in a reliable and highly standardized manner by means of the 50-kHz USV radial maze playback paradigm (Study II: Seffer et al ., 2014). This appears to be particularly relevant for rodent models which are characterized by a deficient social behavior. Post-weaning social isolation is often used in rats as an animal model to induce phenotypes with clinical relevance for neuropsychiatric disorders, such as schizophrenia, which is characterized by a deficit in socio-affective information processing. The impact of social isolation on pro-social ultrasonic communication in rats was investigated, using the 50-kHz USV playback paradigm (Study III: Seffer et al 2015.). It could be shown that post-weaning social isolation specifically impaired the response to 50-kHz USV and did not induce approach behavior in the receiver. Importantly, deficits in approach were reversed by peer-mediated re-socialization and could not be observed after post-adolescent social isolation. Together, these results indicate a critical period for social development during adolescence and highlight the importance of social experience for affiliative behavior.