NGF ANTIBODY-PRODUCTION AS A RESULT OF REPEATED PSYCHOSOCIAL STRESS IN ADULT MICE

Mouse intraspecific fighting, a classic form of psychosocial stress in duced by social isolation, provokes a massive release of salivary NGF into the bloodstream while markedly increasing its synthesis in some h ypothalamic areas. CD-1 male mice were isolated for 8 weeks and tested for aggressive behavior (20-min fighting sessions) twice a week over a period of six months until they were sacrificed and serum levels of antibodies against NGF analyzed. Adrenergic innervation of the iris (n umber of neurites/mm(2)), and NGF (pg/g) levels in the hypothalamus, h ippocampus, and cortex were measured. About 40% of the mice developed antibodies against NGF (Positive mice). The adrenergic innervation of the iris was significantly lower in these mice than in mice that did n ot develop antibodies (Negative mice). In an activity/exploration test , the Positive mice spent significantly less time self-grooming than t he Negative mice. Anti-NGF production might reflect an imbalance cause d by repeated hyperactivation of the homeostatic mechanisms underlying adaptive responses to stress stimuli.