Enhancement of spatial attention in nociceptin/orphanin FQ receptor-knockout mice

Brain Res. 1998 Feb 9;783(2):236-40. doi: 10.1016/s0006-8993(97)01406-6.


We isolated genes for the opioid receptor homologue MOR-C, namely nociceptin receptor (designated alternatively as orphanin FQ receptor) and generated nociceptin receptor-knockout mice. Previously, we have reported that the nociceptin system appears to participate in the regulation of the auditory system. However, the behavior of the nociceptin receptor-knockout mice has yet to be fully characterized. In the present study, we investigated changes in several behavioral performances in mice which lack nociceptin receptor. Nociceptive thresholds of nociceptin receptor-knockout mice were unchanged in the hot-plate and electric foot-shock tests as well as tail-flick and acetic-acid-induced writhing tests compared to those of wild-type mice. The nociceptin receptor-knockout mice did not show any behavioral changes in the elevated plus-maze task. Surprisingly, in the water-finding test, the nociceptin receptor-knockout mice showed an enhanced retention of spatial attention (latent learning) compared to wild-type mice. In a biochemical study, dopamine content in the frontal cortex was lower in nociceptin receptor-knockout mice than wild-type mice. These results suggest that nociceptin receptor plays an important role in spatial attention by regulating the dopaminergic system in the brain.

MeSH terms

  • 3,4-Dihydroxyphenylacetic Acid / analysis
  • Animals
  • Attention / physiology*
  • Behavior, Animal / physiology
  • Brain Chemistry / physiology
  • Dopamine / analysis
  • Dopamine / metabolism
  • Homovanillic Acid / analysis
  • Male
  • Maze Learning / physiology*
  • Mice
  • Mice, Knockout
  • Receptors, Opioid / genetics*
  • Spatial Behavior / physiology*
  • Water


  • Receptors, Opioid
  • Water
  • 3,4-Dihydroxyphenylacetic Acid
  • nociceptin receptor
  • Dopamine
  • Homovanillic Acid