Odor preference and urine-marking scales in male and female rats: Effects of gonadectomy and sexual experience on responses to conspecific odors.

Abstract

Investigation and urine-marking responses of male and female rats toward conspecific urine odors were recorded in pair-wise comparison tests. Each of 16 subject groups was given 15 preference tests, one for each of the possible pairs of 5 urine odors and no-odor control (N). The urine sources were own group (G), intact male (M), castrated male (Mc), ovariectomized female (Fo), and estrous females (F). The results were scaled by using a technique based on Thurstone''s law of comparative judgment. Intact males with sexual experience ordered their odor preferences N < G = M < Mc < Fo = F, and sexually naive males had the order N < G = M < Mc = Fo = F. Only 1 of the 4 groups of castrated males showed scalable investigation preferences. Intact females all showed a common investigation preference scale which was ordered N < G = Fo = F < Mc < M. None of the 4 groups of ovariectomized females showed scalable odor preferences. All 4 groups of intact males urine-marked most over female odors. Gonadectomized subjects, both male and female, showed virtually no urine-marking. Intact females marked, but not differentially over odors. The odor preference results are discussed in relation to the results of 10 previous studies, and the urine-marking results are examined with reference to the use of urine-marking as displays or advertisements, particularly as sex attractants.