DIMETHYL DISULFIDE MIMICS THE EFFECTS OF MILK ON FETAL BEHAVIOR AND RESPONSIVENESS TO CUTANEOUS STIMULI

This study examined the behavioral responses of near-term rat fetuses to a range of chemosensory fluids that resemble constituents of milk or are present in the context of suckling immediately after birth. Milk and dimethyl disulfide (DMDS), a constituent of pup saliva that promotes postnatal nipple attachment, were effective in altering fetal motor activity (increased mouthing and rearlimb movements after infusion), and producing changes in fetal responsiveness to perioral cutaneous stimulation (reduced incidence of facial wiping). The behavioral effects of DMDS were reversed by naloxone and the kappa receptor antagonist nor-binaltorphimine diHCl, suggesting kappa opioid involvement in these behavioral changes. The existence of prenatal responsiveness to DMDS suggests that this substance may function as a semiochemical during the neonatal period.