*Article* **The Effect of Maternal Immune Activation on Social Play-Induced Ultrasonic Vocalization in Rats**

**Kinga Gzielo, Agnieszka Potasiewicz, Ewa Litwa , Diana Piotrowska, Piotr Popik and Agnieszka Nikiforuk \***

Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Behavioral Neuroscience and Drug Development, 12 Sm˛etna Street, 31-343 Kraków, Poland; gzielo@if-pan.krakow.pl (K.G.); potasiew@if-pan.krakow.pl (A.P.); litwa@if-pan.krakow.pl (E.L.); dpiotrow@if-pan.krakow.pl (D.P.); nfpopik@cyf-kr.edu.pl (P.P.)

**\*** Correspondence: nikifor@if-pan.krakow.pl; Tel.: +48-12-662-3374

**Abstract:** Prenatal maternal infection is associated with an increased risk of various neurodevelopmental disorders, including autism spectrum disorders (ASD). Maternal immune activation (MIA) can be experimentally induced by prenatal administration of polyinosinic:polycytidylic acid (poly I:C), a synthetic viral-like double-stranded RNA. Although this MIA model is adopted in many studies, social and communicative deficits, included in the first diagnostic criterion of ASD, are poorly described in the offspring of poly(I:C)-exposed dams. This study aimed to characterize the impact of prenatal poly(I:C) exposure on socio-communicative behaviors in adolescent rats. For this purpose, social play behavior was assessed in both males and females. We also analyzed quantitative and structural changes in ultrasonic vocalizations (USVs) emitted by rats during the play test. Deficits of social play behaviors were evident only in male rats. Males also emitted a significantly decreased number of USVs during social encounters. Prenatal poly(I:C) exposure also affected acoustic call parameters, as reflected by the increased peak frequencies. Additionally, repetitive behaviors were demonstrated in autistic-like animals regardless of sex. This study demonstrates that prenatal poly(I:C) exposure impairs socio-communicative functioning in adolescent rats. USVs may be a useful tool for identifying early autistic-like abnormalities.

**Keywords:** ultrasonic vocalization; maternal immune activation; autism; communication; rat; sex differences; social play; rats
