Psychobiological effects of perinatal exposure to odorants in mice. Part II: Behavioural alterations

Early exposure to odorants pre-, post- or transnatally is known to result in a decreased avoidance or increased preference for these odorants in mammals. There are also indications that olfactory sensitivity for these odorants can be affected. We exposed C57-Bl/6 mice of Mor23-GFP and M71-GFP lines to lyral (LY) or acetophenone (AC), respectively, either transnatally through the water of the mother (1*10-5 M) or postnatally in air for 1 hr per day (20 ll pure). Animals were weaned on postnatal day 20 (P20), and 3 tests were performed: 1) A 3-min exploration test on P20 in a rectangular arena presenting LY and AC under a wire mesh to measure the time spent in each half of the arena. 2) A 2-bottle choice test on P21, whereby LY and AC-flavoured water (1*10-5 M) was provided to assess intake. 3) An olfactory sensitivity test based on an habituation procedure on P21 using two 2-min habituation trials with water and 6 dishabituation trials whereby either LY (in concentrations ranging from 9.77*10-9 to 1.0*10-5 M) or AC (9.54*10-7 to 1.0*10-5 M) was presented to assess time spent exploring and number of visits to the stimuli, assuming increased exploration when the odorant is perceived. Control animals of both lines displayed a preference for LY compared to AC in the exploration test (LY: 99 vs. AC: 81 s, Mor23: p=0.04, M71: p=0.03), while transnatal AC exposure resulted in an absence of preference for either odorant (91 vs. 89 s) and postnatal exposure in a higher preference for AC (78 vs. 108 s, p=0.02). In contrast, LY exposure decreased preference for LY, both trans- and postnatally exposed animals showing no preference for either odour (transnatal: 89 vs. 91; postnatal: 86 vs. 94 s). We furthermore show results of 2-bottle choice test, and the effects of LY and AC exposure on behavioural olfactory sensitivity. These results are linked with density of Mor23- and M71-receptorexpressing olfactory sensory neurons which show high affinity to LY and AC, respectively, presented in the poster by Tazir et al (Part I). This research was supported by a doctoral grant from CNRSRegion Burgundy, and by continued support from Region Burgundy.