Microinjection of morphine into the rostral ventromedial medulla produces greater antinociception in male compared to female rats

Brain Res. 1998 Jun 15;796(1-2):315-8. doi: 10.1016/s0006-8993(98)00353-9.


The antinociceptive and locomotor effects of microinjecting morphine into the rostral ventromedial medulla (RVM) of male and female rats was assessed. Male rats showed greater antinociception than female rats at all doses and times following morphine administration. Male, but not female rats, also showed a dose dependent decrease in locomotion. These data demonstrate that sex differences in antinociception are mediated at least in part by the RVM.

Publication types

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

MeSH terms

  • Animals
  • Female
  • Male
  • Medulla Oblongata / physiology*
  • Microinjections
  • Morphine / pharmacology*
  • Motor Activity / drug effects
  • Narcotics / pharmacology*
  • Nociceptors / drug effects*
  • Rats
  • Rats, Sprague-Dawley
  • Sex Characteristics*


  • Narcotics
  • Morphine