High social anxiety and low aggression in Fawn-Hooded rats

The Fawn-Hooded (FH) rat strain, with well-documented changes in their sero tonergic and noradrenergic systems, is a putative genetic model for some ne uropsychiatric disorders like depression, alcohol abuse, and anxiety. Becau se social phobia frequently occurs in combination with these disorders and there are no social anxiety-related data in FH rats in the literature, we m easured the behavior of FH rats in the social interaction test. In addition , the effects of the anxiogenic Serotonin-2C (5-HT2C) receptor agonist, m-c hlorophenylpipcrazine (m-CPP), were studied. Male FH, Wistar (W), and Sprag ue-Dawley (SD) rats were used in two different test conditions of the socia l interaction test: the high light, unfamiliar arena, associated with high anxiety, and the low light, familiar arena, associated with low anxiety-lik e behavior. All social behaviors were markedly diminished in FH rats that s uggested higher anxiety in these animals. Total social interaction time was reduced by 60-70% in FH rats compared either to W or SD rats under high li ght, unfamiliar or low light, familiar conditions, respectively. Aggressive behavior was reduced at least by 85% in FH rats. Locomotor activity and ex ploratory behavior were only minimally, in most comparisons, not significan tly affected in FH rats. Total social interaction time, aggression, and loc omotor activity were decreased, and self-grooming increased by m-CPP (0.5 m g/kg, ip) in all three strains. m-CPP decreased total social interaction ti me thus, caused anxiety most efficiently in FH rats (reduced by 69%, 50%, a nd 55% in FH, W, and SD rats, respectively), but other effects of the drug were similar in the three strains. Our studies provide evidence that the FH rat strain may be a genetic model of social phobia or other anxiety disord ers with impaired social behavior. (C) 2000 Elsevier Science Inc. All right s reserved.