Enhancement of spatial attention in nociceptin/orphanin FQ receptor-knockout mice.
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.
Mamiya
T
T
Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466, Japan.
Noda
Y
Y
Nishi
M
M
Takeshima
H
H
Nabeshima
T
T
D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000818:Animals; D001288:Attention / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D001923:Brain Chemistry / Q000502:physiology; D004298:Dopamine / Q000032:analysis / Q000378:metabolism; D006719:Homovanillic Acid / Q000032:analysis; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D011957:Receptors, Opioid / Q000235:genetics*; D013037:Spatial Behavior / Q000502:physiology*; D014867:Water; D000094942:Nociceptin Receptor
D011957:Receptors, Opioid; D014867:Water; D015102:3,4-Dihydroxyphenylacetic Acid; D004298:Dopamine; D006719:Homovanillic Acid; D000094942:Nociceptin Receptor; C000722287:Oprl1 protein, mouse