title: Circadian rhythm in rat brain opiate receptor.
abstract: To investigate diurnal variations in opiate receptor binding, the amount of specifically bound [3H]naloxone was measured at 4-h intervals across a 24-h period in the forebrains of rats that had been housed under a controlled light--dark cycle (lights on from 07.00 to 19.00 h) for 3 weeks. A significant rhythm with a peak at 22.00 h was found, the amplitude was 46--78%. In the absence of time cues, this circadian rhythm persisted with a peak at 02.00--06.00 h and an amplitude of 88%. Scatchard analysis indicated that the differences in binding throughout the day were due not to changes in affinity, but to changes in the number of binding sites.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002940:Circadian Rhythm; D003624:Darkness; D007700:Kinetics; D008297:Male; D009270:Naloxone / Q000378:metabolism; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone