[Behavioral consequences of isolation in early ontogeny in rats: selectivity of anxiety conditions]

Multiparameter scale for evaluation of anxiety-phobic state in rats reveals significant enhancement of anxiety in rat pups after 6-week isolation (beginning from the 21st day from birth) as compared to grouped controls of the same litter: the locomotion and exploration that appear in test areas are suppressed, and species-specific fear reactions are enhanced. These changes considered as signs of situational anxiety are not eliminated by 2.5-month keeping in groups. Nevertheless, they are not correlated with parameters of the acoustic startle reflex that (by the data of literature) is thought to be related with fear and anxiety. On the basis of the discrepancy it is proposed that state of anxiety is selective. This suggestion is confirmed by individual behavioral variations characterized by a combination of a low level of situational anxiety and a high level of acoustic anxiety observed in both experimental and control groups. These variations may explain the existence of atypical "emotional resonance"-like behavior according to P.V. Simonov. Attention is given to selectively enhanced acoustic startle reflex in the group of active control as an evidence for critical importance of any manipulations with social context in early ontogeny.