A GENETIC AND MULTIFACTORIAL ANALYSIS OF ANXIETY-RELATED BEHAVIORS INLEWIS AND SHR INTERCROSSES

Lewis (LEW) and spontaneously hypertensive rats (SHR) have been shown to differ in a series of fear-related behaviours measured in different anxiety/emotionality tests. In the present study, we have investigate d some of the genetic mechanisms underlying these differences. To this end, male and female rats from the two inbred strains were crossed to produce two parental (LEW and SHR), two Fl (LEW or SHR mother), and t wo F2 (LEW or SHR grandmother) groups. All rats were tested in the ele vated plus-maze and in the open field, besides being characterised for systolic blood pressure (BP). LEW rats approached the open arms of th e plus-maze and the central area of the open held less than SHRs. The two strains also differed in their BP (SHR > LEW). LEW/SHR differences were found to be due to direct effects of the genes, rather than to i ndirect maternal and grand-maternal effects. Central locomotion in the open field was shown to be the most heritable of all the traits consi dered herein. A factor analysis on the segregating F2 population produ ced three independent factors. The first one was associated to measure s of anxiety from the elevated plus-maze, and the second to measures o f locomotion in novel environments. Factor scores revealed that the pa rental strains differ in relation to the first but not to the second f actor. This study demonstrates the usefulness of coupling genetic and multifactorial methods to investigate behavioural traits and it confir ms LEW and SHR strains as an interesting genetic tool for the study of anxiety. (C) 1998 Elsevier Science B.V. All rights reserved.