The blind mole rat, Spalax, is a subterranean rodent with atrophied, subcutaneous eyes. Whereas most of the visual system is highly degenerated, the retino-hypothalamic pathway in this species has remained intact. Although Spalax is considered to be visually blind, circadian locomotor rhythms are entrained by the light/dark cycle. In the present study we used anterograde tracing techniques to demonstrate retinal afferents to the suprachiasmatic nucleus (SCN) and immunohistochemistry to examine the distribution of neuropeptides that are known to be involved in the regulation or expression of circadian rhythmicity. Based on the localization of retinal afferents and neuropeptides, the SCN can be divided into two subdivisions. The ventral region, which receives retinal afferents, also contains vasoactive intestinal polypeptide (VIP)-containing neurons, and fibers that are immunopositive to neuropeptide Y (NPY) and serotonin (5-HT). The dorsal region contains vasopressinergic neurons, but this latter cell population is extremely sparse compared to that described in other rodents. The dorsal region is also characterized by numerous VIP-immunoreactive fibers. The presence of NPY and 5-HT fibers suggests that the SCN receives afferent projections from the intergeniculate leaf-let and from the raphe nuclei, respectively. These neuroanatomical results, together with previous studies of behavior, visual tract tracing, and immediate early gene expression, confirm that an endogenous clock and the capacity for light entrainment of circadian rhythms are conserved in the blind mole rat.
|Number of pages||7|
|Journal||Brain Research Bulletin|
|State||Published - 1997|
Bibliographical noteFunding Information:
We would like to thank Christel Merrouche for help with histology, and Ghislaine Claine for care of the animals. The research was funded by grants from Human Frontier (RG95/68), NATO (#950334), ENP (#185), and BIOMED2 (PL/962327).
- Circadian system
- Neuropeptide Y
- Subterranean mammal
- Vasoactive intestinal polypeptide
ASJC Scopus subject areas
- Neuroscience (all)