Housing influences exploration and social interaction of control and DSP-4-treated rats

Exploratory behavior and social interaction were investigated in rats that were reared in different social environments following neonatal injection with either water vehicle or the norepinephrine neurotoxin, DSP-4. At weaning, they were placed in a familiar or novel bedding type and were housed in either vehicle control-only, DSP-4-only, or mixed vehicle control and DSP-4 groups for 10 days. They were then observed in three different situations: the home cage, the cage of an unfamiliar rat, and an open field. Compared to rats housed in vehicle control-only or DSP-4-only groups, rats housed in mixed DSP-4 and vehicle control groups showed elevated exploration behavior in the home cage. Also, rats housed in mixed groups in the familiar bedding, but not the novel one, showed abnormally low levels of rearing in an open field test and reduced social interaction with unfamiliar rats. The implications of these results for a new animal model of anxiety are discussed.