MATURATION OF THE BEHAVIORAL AND NEUROENDOCRINE DIFFERENCES BETWEEN THE ROMAN RAT LINES

The behavioral and/or neuroendocrine reactivity to psychological (open -field exposure) and physiological (CRF challenge) stimulations, as we ll as adrenal tyrosine hydroxylase (TH) and phenylethanolamine N-methy l transferase (PNMT) activities were measured, at different ages, in t he Roman high avoidance (RHA) and Roman low avoidance (RLA) rat lines that have been genetically selected on the basis of their divergent ac tive avoidance behavior. The highest locomotor activity in the open fi eld, associated to blunted prolactin and renin reactivity to an emotio nal stress and lower specific TH and PNMT activities, characterized th e RHA rats of all ages. HPA axis reactivity to psychological and/or ph ysiological stimulations was identical in young animals (14 weeks old) of the two lines. Nevertheless, it displayed with age maturation proc esses, since the amplitude of postopen-field secretion peak for ACTH w as larger in RLA rats from 20 weeks on, the response to CRF being not increased until 42 weeks. These maturation processes could result from genetically influenced changes related to environmental stimulations. Therefore, the Roman lines may be an excellent model to study the int eractions between the genetic and developmental factors controlling th e coupling between both behavioral and neuroendocrine functions.