Pretreatment circadian period in free-running blind people may predict thephase angle of entrainment to melatonin

To date, we have entrained (synchronized) eight totally blind people with f ree-running circadian rhythms to a nightly dose of 10 mg of melatonin. Each person entrained at a different phase angle of entrainment (PAE), which is the interval in hours between the time of the melatonin dose and the time of the endogenous melatonin onset. When the PAE was plotted against the pre treatment free-running (i.e. slightly different than 24.0 h) circadian peri od (tau), the fitted regression line revealed a significant correlation, wh ich is consistent with previous findings on light entrainment of rest-activ ity rhythms in free-running rodents [Pittendrigh and Daan, J. Comp. Physiol ., 106 (1976) 291-331]. (C) 2001 Elsevier Science Ireland Ltd. All rights r eserved.