Early programming of astrocyte organization in the mouse suprachiasmatic nuclei by light.
The principal pacemaker in mammals, controlling physiology and behavior, is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Early photic experience has long-term effects on the animal's rhythmic behavior, as indicated by alterations in the phase shift induced by a light pulse, and in the expression of the circadian rhythm of locomotor activity under light-dark (LD), constant light (LL), and constant darkness (DD) environments. However, the brain substrates targeted by early light have not yet been identified. Possible candidates are astrocytes, as they develop postnatally in parallel to the circadian system, and are involved in SCN function by modulating intercellular communication and mediating photic input. Here, we reared three groups of mice under different light environments (LD, LL, and DD) during the suckling period. Later on, all mice were entrained to LD, and we determined associated astrocytic modifications by examining the expression of glial fibrillary acidic protein (GFAP) in the SCN. We observed that although LL-reared mice showed lowest GFAP expression in the SCN, as determined by quantification of immunostaining levels, the number of GFAP-positive cells was highest in this group, suggesting structural remodelling of SCN astrocytes by early light experience. These results indicate the postnatal light environment has long-term effects on the astrocytic population of the SCN. We argue that these neurochemical and structural alterations may affect clock function, which may in turn modify animal behavior
Canal
Maria Mercè
MM
Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK. maria.canal@manchester.ac.uk
Mohammed
Nimco Mose
NM
Rodríguez
José Julio
JJ
D000818:Animals; D000833:Animals, Suckling; D001253:Astrocytes / Q000502:physiology* / Q000528:radiation effects*; D001683:Biological Clocks; D005786:Gene Expression Regulation / Q000502:physiology / Q000528:radiation effects; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism; D008027:Light; D051379:Mice; D008810:Mice, Inbred C57BL; D017440:Photoperiod; D013493:Suprachiasmatic Nucleus / Q000166:cytology*
D005904:Glial Fibrillary Acidic Protein