Effects of Preweaning Exposure to Novel Maternal Odors on Maternal Responsiveness and Selectivity in Adulthood Akeel Shah Gina Oxley Vedran Lovic Alison S. Fleming Department of Psychology University of Toronto Mississauga, Ontario, L5L 1C6 Canada Received 14 July 2001; Accepted 28 September 2001 ABSTRACT: We examined the effects of odor exposure in the nest on the offspring’s subsequent adult responsivity to pups scented with the same odor or a different odor. It was hypothesized that animals receiving exposure to the odor in the nest would be more maternally responsive to pups scented with the (same) exposed odor than to unscented (water-scented) pups. In the first part of the study (Part A), Sprague-Dawley female rat pups (days 1–18 of age) either received exposure to an artificial lemon odor or to the natural (water) odor in the nest. In the second part of the study (Part B), rat pups were exposed daily to lemon or neutral odorants in an incubator at a distance from the mother and the nest. On day 21, animals received odor preference tests for lemon versus neutral pine bedding. On day 60, animals were mated and their pups were removed at 15-min intervals at the time of parturition. Animals were then tested for maternal behavior to foster pups on day 1 or 7 after parturition. Foster pups were scented either with the lemon odor or with water (unscented). Early exposure to lemon in the nest context enhanced animals’ attraction to the lemon odor in juvenile tests. In adult maternal tests, exposure to odor on the mother and in the nest had two effects. It increased the latency for animals to express maternal behavior; however, once mothers expressed maternal behavior, they spent more time licking and crouching over pups scented with the same odorant to which they had been exposed earlier on their own mothers. Simple exposure to the lemon odorant out of context of the nest had no effect on adult maternal latencies or behavior. ß 2002 Wiley Periodicals, Inc. Dev Psychobiol 41: 187–196, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/dev.10064 Keywords: maternal behavior; development; olfactory experience; rats; preweaning experience; maternal selectivity Mammals typically express a stereotyped set of behavioral responses to their newly born offspring under the influence of the hormones associated with late pregnancy and parturition (Fleming, O’Day, & Kraemer, 1999; Numan, 1994). In the rat, the main components of maternal behavior are retrieval of pups to the nest site, nest building, licking and nursing of pups (Wiesner & Sheard, 1933). Although hormon- es associated with parturition are clearly important for the rapid expression of maternal behavior at birth, they are not necessary (Fleming & Rosenblatt, 1974a; Correspondesce to: A. S. Fleming E-mail: fleming@psych.utoronto.ca Contract grant sponsor: NSERC (to A.S.F) ß 2002 Wiley Periodicals, Inc.