Calbindin and Fos within the suprachiasmatic nucleus and the adjacent hypothalamus of Arvicanthis niloticus and Rattus norvegicus

doi:10.1016/S0306-4522(00)00212-8

Neuroscience

Volume 99, Issue 3, 16 August 2000, Pages 565-575

https://doi.org/10.1016/S0306-4522(00)00212-8 Get rights and content

Abstract

The suprachiasmatic nucleus is the site of the primary circadian pacemaker in mammals. The lower sub paraventricular zone that is dorsal to and receives input from the suprachiasmatic nucleus may also play a role in the regulation of circadian rhythms. Calbindin has been described in the suprachiasmatic nucleus of some mammals, and may be important in the control of endogenous rhythms. In the first study we characterized calbindin-expressing cells in the suprachiasmatic nucleus and lower sub-paraventricular zone of nocturnal and diurnal rodents. Specifically, Rattus norvegicus was compared to Arvicanthis niloticus, a primarily diurnal species within which some individuals exhibit nocturnal patterns of wheel running. Calbindin-immunoreactive cells were present in the suprachiasmatic nucleus of Arvicanthis and were most concentrated within its central region but were relatively sparse in the suprachiasmatic nucleus of Rattus. Calbindin-expressing cells were present in the lower sub-paraventricular zone of both species. In the second study we evaluated Fos expression within calbindin-immunoreactive cells in nocturnal Rattus and in Arvicanthis that were either diurnal or nocturnal with respect to wheel-running. All animals were kept on a 12:12 light/dark cycle and perfused at either 4 h after lights-on or 4 h after lights-off. In the suprachiasmatic nucleus in both species, Fos expression was elevated during the day relative to the night but less than 1% of calbindin cells contained Fos in Arvicanthis, compared with 13–17% in Rattus. In the lower sub-paraventricular zone of both species, 9–14% of calbindin cells expressed Fos, and this proportion did not change as a function of time. Among Arvicanthis, the number of calbindin expressing neurons in the lower sub-paraventricular zone was influenced by an interaction between the wheel running patterns (nocturnal vs diurnal) and time of day. Thus, the number of calbindin-positive cells within the suprachiasmatic nucleus differed in Arvicanthis and Rattus, whereas the number of calbindin-positive cells within the lower sub-paraventricular zone differed in nocturnal and diurnal Arvicanthis.

Our examination of R. norvegicus and A. niloticus suggests potentially important relationships between calbindin-containing neurons and whether animals are nocturnal or diurnal. Specifically, rats had more Fos expression in calbindin containing cells in the suprachiasmatic nucleus than Arvicanthis. In contrast, Arvicanthis exhibiting diurnal and nocturnal patterns of wheel-running differed in the number of calbindin-containing cells in the lower sub-paraventricular zone, dorsal to the suprachiasmatic nucleus.

Section snippets

Animals

We used adult (>60 days) A. niloticus bred in the laboratory from a stock descended from 29 individuals originally trapped in Kenya in 1993.¹⁵ In addition, we used adult male Rattus (Charles River Laboratories, Cambridge, MA, USA). All animals were kept in a 12:12 LD cycle, singly housed in Plexiglas cages (38×34×16 cm) and provided with water and food (Harlan 8640 Teklad, Madison, WI, USA) ad libitum. A red light (<5 lux) remained on constantly for the purposes of animal care. All experiments

Suprachiasmatic nucleus of Arvicanthis niloticus

CALB-immunoreactive expression within a section through the central SCN of a representative Arvicanthis is depicted in Fig. 2A. There was a very distinct pattern of CALB-immunoreactivity within the SCN; the most centrally located CALB-immunoreactive neurons were more densely concentrated and darkly stained than the CALB-immunoreactive neurons in the more peripheral regions of the nucleus (Fig. 2A). We saw no obvious differences between males and females with respect to the distribution of

Discussion

The distribution of CALB-immunoreactive cells within the SCN of Arvicanthis was similar in some respects to that described in M. auratus. Specifically, in both species the central portion of the SCN contained the highest concentration of darkly stained CALB-immunoreactive cells.⁴⁶ These two species differed slightly in that more lightly stained CALB-immunoreactive cells were found outside the central portion of the SCN in Arvicanthis (2., 3.) than in M. auratus.⁴⁶ Far more cells positive for

Acknowledgements

The authors would like to thank Teresa McElhinny, Betty Gubik, Colleen Novak, and Sandra Rose for their valuable assistance and advice. The research described in this paper was supported by NIMH RO1-MH053433 to L.S. and NSF IBN 9514374 to A.A.N.

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Calbindin and Fos within the suprachiasmatic nucleus and the adjacent hypothalamus of Arvicanthis niloticus and Rattus norvegicus

Abstract

Section snippets

Animals

Suprachiasmatic nucleus of Arvicanthis niloticus

Discussion

Acknowledgements

Trends Neurosci.

Neuroscience

Brain Res. Bull.

Expl Neurol.

J. Chem. Neuroanat.

Brain Res.

Brain Res.

Neurosci. Lett.

Neurosci. Lett.

Physiol. Behav.

Brain Res.

Brain Res.

Neuroscience

Brain Res.

Brain Res.

Neuroscience

Neuroscience

Neurosci. Res.

Brain Res.

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