Daily changes in GFAP expression in radial glia of the olfactory bulb in rabbit pups entrained to circadian feeding

Jan 29, 2020Physiology & behavior

Daily changes in support cell protein levels in the smell system of rabbit pups linked to feeding times

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Abstract

GFAP protein expression in the olfactory bulb of rabbit pups shows a nadir at feeding time and a peak 16 hours after feeding.

Food restriction to specific times may uncouple circadian rhythms from light cues.
Astrocytes in the suprachiasmatic nucleus are implicated in regulating circadian rhythms.
GFAP expression and the morphology of radial glia processes change in relation to feeding times.
The timing of GFAP changes is in anti-phase to locomotor activity and neuronal activity markers.
These findings suggest a potential role for glial cells in synchronizing circadian rhythms with feeding.

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When food is restricted daily to a fixed time, animals show uncoupled molecular, physiological and behavioral circadian rhythms from those entrained by light and controlled by the suprachiasmatic nucleus. The loci of the food-entrainable oscillator and the mechanisms by which rhythms emerge are unclear. Using animals entrained to the light-dark cycle, recent studies indicate that astrocytes in the suprachiasmatic nucleus play a key role in the regulation of circadian rhythms. However, it is unknown whether astrocytic cells can be synchronized by circadian restricted feeding. Studying the olfactory bulb (OB) of rabbit pups entrained to daily feeding, we hypothesized that the expression of glial fibrillary acidic protein (GFAP) and the morphology of GFAP-immunopositive cells change in synchrony with timing of feeding. By using pups fed at 1000 h or 2200 h, we found that GFAP protein expression in the OB changes with a nadir at feeding time and a peak 16 h after feeding. We also found that length of radial glia processes, the most abundant GFAPcell in the rabbit pup OB, shows a daily change also coupled to feeding time. These temporal changes of GFAP were expressed in anti-phase to the rhythms of locomotor activity and c-Fos immunoreactivity. The results indicate that GFAP expression and elongation-retraction of radial glia processes are coupled by feeding time and suggest that glia cells may play an important functional role in food entraining of the OB circadian oscillator. +

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Daily changes in GFAP expression in radial glia of the olfactory bulb in rabbit pups entrained to circadian feeding

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