Strain-Dependent Differences in Responsiveness of Mice to Nitrous Oxide (N2O) Antinociception
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N2O antinociception was assessed in eight inbred and two outbred mouse strains. Results indicated the following order of responsiveness among the 10 strains: A/J (most sensitive), C57BL/6ByJ, C57BL/6J, BALB/cByJ, C3H/HeJ, Swiss-Webster, CXBK/ByJ, ICR, CBA/J and DBA/2J (least sensitive). These results demonstrate significant strain-dependent differences in antinociceptive responsiveness to N2O. The weak antinociceptive response to N2O in the DBA/2J strain, which is sensitive to morphine and U-50,488H, indicates some underlying neurobiological difference in the DBA/2J mouse that imparts resistance to N2O. The responsiveness of CXBK/ByJ mice to N2O indicates that μ-opioid receptors may not play an important role in N2O antinociception in mice.