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The aim of the current study was to investigate the association between expression of acoustic startle response and fear-induced aggression. The intensity of aggressive response towards man and acoustic startle response in adult and 15-day old Norway rats selectively bred for 70 generation for high level or the lack of fear-induced aggression was studied. Adult rats of aggressive strain demonstrated high aggression and increased amplitude of acoustic startle response compared to rats selectively bred for the lack of fear-induced aggression. It was found that, in contrast to infant rats of tame strain, 15-day old rat pups of aggressive strain demonstrated distinct aggressive response towards man, although this response was not as intensive as in adult rats of this strain. There was no considerable difference between aggressive and tame infants in amplitude of acoustic startle response. Significant habituation of startle response was shown in adult rats of aggressive strain, whereas in 15-day old rat pups of aggressive rat strain amplitude of startle response remained unaltered. Both adult and infant rats of tame strain demonstrated considerable habituation of startle response. Thus, defensive aggression in rats with genetic predisposition to fear-induced aggression appears quite early--at eyes opening they demonstrate a pronounced aggressive response toward man. The acoustic startle reflex is one of the elements of complex behavior--fear-induced aggression, and this element is involved in the enhancement of aggressive response towards man in adult rats but does not play any essential role in infant aggressiveness.

We studied the influence of recombinant DNA containing the cloned angiogenin gene, plasmid DNA without angiogenin gene, and purified recombinant angiogenin injected to Tg8 mice at the age of two days on the body mass of 28- and 40-day old mice. The body mass of mice that were injected with the cloned angiogenin gene or purified angiogenin was less than in the control mice. The body mice of Tg8 mice injected with recombinant DNA containing the cloned angiogenin gene did not increase from day 28 to day 40, while in the mice with purified recombinant angiogenin and control mice it increased by 24 and 57%, respectively. These data suggest that the elevated level of angiogenin at the early developmental stages inhibits the increase of body mass. The effect we described is related, in al likelihood, to the known inhibitory effect of angiogenin on protein synthesis.