[The dynamic circadian mobility of rats under acute and chronic propranolol administration]

Acute administration of propranolol, 1 mg/kg i.p., decreased the amplitude of locomotor circadian rhythm in rats and shifted its acrophase to late night hours. After chronic (10-day) treatment with the drug, morning rises in locomotion after turning out the light became less frequent. The circadian rhythm reorganization observed may depend on the effects of the beta-adrenoblocker on its specific receptors in the hypothalamic suprachiasmatic nuclei and/or the pineal gland.