STRAIN-DEPENDENT DIFFERENCES IN RESPONSIVENESS OF MICE TO NITROUS-OXIDE (N2O) ANTINOCICEPTION

N2O antinociception was assessed in eight inbred and two outbred mouse strains. Results indicated the following order of responsiveness amon g the 10 strains: A/J (most sensitive), C57BL/6ByJ, C57BL/6J, BALB/cBy J, C3H/HeJ, Swiss-Webster, CXBK/ByJ, ICR, CBA/J and DBA/2J (least sens itive). These results demonstrate significant strain-dependent differe nces in antinociceptive responsiveness to N2O. The weak antinociceptiv e response to N2O in the DBA/2J strain, which is sensitive to morphine and U-50,488H, indicates some underlying neurobiological difference i n the DBA/2J mouse that imparts resistance to N2O. The responsiveness of CXBK/ByJ mice to N2O indicates that mu-opioid receptors may not pla y an important role in N2O antinociception in mice.