Daily Rhythms of Fos Expression in Hypothalamic Targets of the Suprachiasmatic Nucleus in Diurnal and Nocturnal Rodents

Little is known about the differences in the neural substrates of circadian rhythms that are responsible for the maintenance of differences between diurnal and nocturnal patterns of activity in mammals. In both groups of animals, the suprachiasmatic nucleus (SCN) functions as the principal circadian...

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Bibliographic Details
Published in:Journal of biological rhythms 1999-08, Vol.14 (4), p.300-306
Main Authors: Nunez, Antonio A., Bult, Abel, McElhinny, Teresa L., Smale, Laura
Format: Article
Language:English
Subjects:
Animals
Arvicanthis niloticus
Behavior, Animal - radiation effects
Circadian rhythm
Circadian Rhythm - physiology
Circadian Rhythm - radiation effects
Darkness
Hypothalamus - metabolism
Hypothalamus - physiology
Male
Muridae
Proteins
Proto-Oncogene Proteins c-fos - biosynthesis
Rats
Rats, Sprague-Dawley
Rodents
Sleep - physiology
Suprachiasmatic Nucleus - metabolism
Suprachiasmatic Nucleus - physiology
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Summary:Little is known about the differences in the neural substrates of circadian rhythms that are responsible for the maintenance of differences between diurnal and nocturnal patterns of activity in mammals. In both groups of animals, the suprachiasmatic nucleus (SCN) functions as the principal circadian pacemaker, and surprisingly, several correlates of neuronal activity in the SCN show similar daily patterns in diurnal and nocturnal species. In this study, immunocytochemistry was used to monitor daily fluctuations in the expression of the nuclear phosphoprotein Fos in the SCN and in hypothalamic targets of the SCN axonal outputs in the nocturnal laboratory rat and in the diurnal murid rodent, Arvicanthis niloticus. The daily patterns of Fos expression in the SCN were very similar across the two species. However, clear species differences were seen in regions of the hypothalamus that receive inputs from the SCN including the subparaventricular zone. These results indicate that differences in the circadian system found downstream from the SCN contribute to the emergence of a diurnal or nocturnal profile in mammals.
ISSN:0748-7304
1552-4531
DOI:10.1177/074873099129000713