Effects of melatoninergic agonists on light-suppressed circadian rhythms in rats.

This study addressed the question whether light-suppressed circadian rhythms in cardiovascular parameters in rats could be restored by melatonin and a synthetic analogue. Blood pressure, heart rate, and locomotor activity were monitored by radiotelemetry in six Sprague-Dawley rats. After synchronization to a 12:12 light/dark (LD) schedule (lights on at 0700 hours, 100 lux), rats were kept in constant light (LL) of low intensity (5-10 lux) for 11 weeks.