BEHAVIORAL DISTURBANCES IN ADULT CD-1 MICE AND ABSENCE OF EFFECTS ON THEIR OFFSPRING UPON SO2 EXPOSURE

Adult male and female CD-1 mice were exposed to different SO2 concentr ations (0, 5, 12, or 30 ppm) for 24 days, from 9 days before the forma tion of breeding pairs to pregnancy day 12-14. This exposure was near- continuous, covering about 80% of the total time indicated. The offspr ing of exposed darns were cross-fostered shortly after birth to dams n ot previously exposed. Videorecordings of the adult subjects' activiti es during the first hour after the start of exposure showed marked, ac ute transient behavioural effects such as increase of rearing and soci al interactions, which were more pronounced in males than in females. Subsequent activity tests on exposure days 3, 6, and 9 showed subacute effects including a dose-dependent decrease of grooming and an increa se of digging as well as changes in chamber crossing and wall-rearing which were not dose-dependent; most of these effects were more pronoun ced in females than in males. Food and water consumption and body weig ht declined in a dose-dependent fashion only after the formation of br eeding pairs, when consummatory responses were enhanced in the control s. Reproductive performance as well as postnatal somatic and neurobeha vioural development of the offspring (the latter assessed by an observ ational test battery including eight reflexes and responses) were not affected by SO2. Passive avoidance acquisition and retention at the yo ung adult stage (60 days) and response changes produced by repeated ap paratus exposure in non-reinforced animals (habituation) were similarl y unaffected. Overall, the data indicate that SO2 produces transient, acute behavioural disturbances and more subtle subacute response chang es in adult mice which may be due, at least partly, to a functional in terference with olfactory modulation of mouse behaviour. The absence o f effects on reproductive performance and neurobehavioural development of the offspring suggests that the risk to the developing organism fr om gestational SO2 exposure is low.