Bradycardiac responses elicited by alcohol odor in rat neonates: influence of in utero experience with ethanol.

Two experiments were performed in order to assess neonatal responsiveness to alcohol odor as a function of prior acute in utero experience with this drug. In experiment 1 the amniotic fluid surrounding rat fetuses of 21 days of gestation was either contaminated with alcohol or lemon solutions or with physiological saline. Neonatal presentation of alcohol odor induced stable and relatively low cardiac decelerations in saline and lemon exposed rats. Alcohol prenatal administration resulted in stronger bradycardiac patterns that lasted throughout most of the testing procedure. In experiment 2 these results were replicated and it was observed that nociceptive stimulation paired with alcohol prenatal administration significantly inhibited neonatal responsiveness to ethanol odor. The results indicate that learning relative to alcohol derived cues is likely to occur in utero. Furthermore, expression of acquisition is detected almost immediately after birth when employing an autonomic index frequently related with orienting responses to relevant stimuli.