The electrolytic lesions of raphe or locus coeruleus (I = 1-1.5 mA, 20 sec, with a change in polarity) produce a destabilization in the circadian rhythms of the active searching behaviour (tested in the "open field") in rats kept under conditions of natural illumination in the period of the winter or summer solstice. The daily or circadian components are substituted, respectively, for the ultra- or infradian rhythms. If the animals are kept for 10 days under 24-h light or dark conditions, the serotoninergic or noradrenergic deficit delays the formation of free-running rhythms.
Animals Circadian Rhythm