Effect of dorsal midbrain lesion in infant rats on development of circadian rhythm.
To investigate the relationship between serotonergic system and development of the circadian rhythm, we made destruction of the dorsal region of midbrain including dorsal raphe nuclei in neonatal rat pups. Overt circadian rhythms of locomotor activity and water consumption were clearly observed at 4-6 weeks of age, in both the sham operated and the lesioned pups. However, amount of both activities in the lesioned pups was significantly larger than that of the sham operated pups during the light phase. This indicates that the circadian activity rhythm is altered by the lesion, although the degree of alteration is slight. This suggests the involvement of the serotonergic system in the full development of the normal circadian rhythm. An irregular drinking pattern was observed in the lesioned rats at 5 months of age, although a light-dark difference in water consumption was evident. It takes longer for lesioned adult rats to manifest a significant day-night difference in water consumption, than for sham operated rats after reversal of light-dark cycle. This suggests that a lesion in the dorsal midbrain made during the neonatal period may cause a permanent change in the circadian system.
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood; D004327:Drinking Behavior / Q000502:physiology; D005260:Female; D008124:Locomotion; D008636:Mesencephalon / Q000502:physiology*; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*
D012701:Serotonin; D003345:Corticosterone