Milk-induced analgesia and comforting in 10-day-old rats: opioid mediation

Pharmacol Biochem Behav. 1988 Jan;29(1):9-13. doi: 10.1016/0091-3057(88)90266-3.


The effects of slow intraoral milk infusions on the opioid-mediated behaviors of ultrasonic vocalizations and paw removal from a hot plate (48-49 degrees C) were evaluated in 10-day-old rats. Milk reduced distress vocalization by circa 30% while increasing paw lift latencies by about 60%. Alterations in both behaviors were fully reversed by naltrexone (0.5 mg/kg) pretreatments. These data demonstrate the calming and analgesic effects of milk. Implications for a possible role of opioid peptides in mother-young relationships are discussed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acoustic Stimulation
  • Analgesia*
  • Animals
  • Female
  • Milk*
  • Naltrexone / pharmacology
  • Rats
  • Rats, Inbred Strains
  • Receptors, Opioid / physiology*
  • Ultrasonics
  • Vocalization, Animal / drug effects


  • Receptors, Opioid
  • Naltrexone