Rat fetuses respond to chemical stimuli in gas phase.

Fetuses exhibit behavioral responses to intraoral infusions of chemical solutions presented in liquid phase, including an increase in overall activity and the production of a species-typical action pattern, facial wiping. A series of experiments were conducted in which chemical compounds with strong olfactory characteristics--citral and cyclohexanone--were presented in gas phase to rat fetuses on day 20 of gestation. Fetuses exhibited similar behavioral responses to stimuli presented in liquid and gas phases, suggesting a common basis for the processing of prenatal chemosensory information. Chemosensory stimuli in gas phase are sufficient to elicit both behavioral activation and a stereotypic action pattern of the rat fetus, patterns that anticipate postnatal olfactory-directed behavior. These results suggest that prenatal chemosensory experience, which normally occurs in an aqueous medium, may be relevant to the development of postnatal behavior that is directed by airborne olfactory cues.