Developmental brain injury associated with abnormal play behavior in neonatally Borna disease virus-infected Lewis rats: a model of autism

Play behavior, nonsocial exploratory activity, and nonplay social interacti on were observed in male juvenile Lewis rats with brain developmental injur y following neonatal infection with Borna disease virus (BDV). These behavi ors were tested using the 'intruder-resident' paradigm, with social isolati on of residents for six days prior to testing. Four experimental pairings o f infected (BDV) and uninfected (NL) rats were studied as follows: NL-NL; N L-BDV; BDV-NL; and BDV-BDV (the first member is the resident, the second me mber is the intruder). Observation of social activities was carried out for 10 min on two consecutive days, Nonsocial exploratory activity (e.g, ambul ation and rearing) was similar in BDV and NL residents. Duration of nonplay social investigation (e.g. sniffing, approach, and follow) was higher in B DV residents as compared to NL residents when tested on the first test day. On the second day, all rats showed similar level of nonplay social interac tion. When confronted with NL intruders, NL residents exhibited significant ly more play behavior compared to the NL-BDV, BDV-NL and BDV-BDV pairs, whe n play behavior was measured by the number of 'pins'. Moreover, irrespectiv e of a type of intruder, NL residents demonstrated higher play soliciting b ehavior than BDV residents, indicating attenuated readiness to play in BDV- infected rats. The number of pins and play solicitations in BDV-NL pairs si gnificantly increased over the two days of testing, while play activity in NL-BDV pairs declined on the second test day. This pattern suggests that th e degree of social reinforcement on the first day of testing affected the l evel of play on the second day. These data demonstrate deficits in play beh avior and other social interactions following BDV-associated developmental brain injury, thus supporting the value of the neonatally BDV-infected rat as an animal model of autism. (C) 1999 Elsevier Science B.V. All rights res erved.