Circadian locomotor rhythms in mice with targeted disruption of the gene for the carbon monoxide synthesizing enzyme, heme oxygenase-2


Journal Article

Carbon monoxide (CO), generated in neurons by the enzyme heme oxygenase- 2 (HO2), is postulated to be a gaseous signaling molecule in the mammalian brain. Because of the recent evidence suggesting an important role of another endogenously produced gas, nitric oxide (NO), in entrainment of circadian rhythms in mammals, we hypothesized that CO may also be involved in regulating these rhythms. Consistent with this idea, others have found a circadian rhythm of heme turnover and CO synthesis can be induced by bright light. Furthermore, HO2 is co-localized with guanylyl cyclase, the putative target of CO, throughout the brain, with high amounts of staining in the suprachiasmatic nucleus (SCN) of the hypothalamus. The goal of the present study was to evaluate the role of CO in photic entrainment in wild-type and HO2 deficient mice. HO2-/- mice did not display any abnormalities in circadian rhythmicity: Entrainment to a light-dark cycle, the ability to phase delay locomotor activity after a four hour phase shift in photoperiod, and the period of the free running rhythm (t) were similar between HO2-/- and wild-type mice. Taken together, these data suggest that CO does not play a major role in regulating circadian activity rhythms in mice.

Full Text

Duke Authors

Cited Authors

  • Demas, GE; Kriegsfeld, LJ; Poss, KD; Tonegawa, S; Nelson, RJ

Published Date

  • October 27, 1999

Published In

Volume / Issue

  • 30 / 3

Start / End Page

  • 282 - 289

International Standard Serial Number (ISSN)

  • 0929-1016

Digital Object Identifier (DOI)

  • 10.1076/brhm.

Citation Source

  • Scopus