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Behavioral effects following ablation of retinal ganglion cells in diurnal grass rats

Fogo G, Gall AJ (2017) Behavioral effects following ablation of retinal ganglion cells in diurnal grass rats. Neuroscience 2017 Abstracts 237.03 / HH34. Society for Neuroscience, Washington, DC.

Summary: Light influences behavior and physiology in mammals by entraining circadian rhythms and also through direct and acute inhibition or stimulation of activity, a process called masking. Although there has been substantial progress elucidating the mechanisms responsible for the workings of the circadian system in nocturnal species, less is known about the mechanisms that support the diurnal profile of activity of mammals, especially as they relate to the retina. We recently showed that the intergeniculate leaflet (IGL) is critical for the display of normal patterns of daily activity in diurnal grass rats (Arvicanthis niloticus). Specifically, IGL lesions reverse the activity patterns of these animals such that they became night-active; this occurred through their effects on both circadian mechanisms and masking. The IGL is a thalamic structure that receives direct inputs from the melanopsin containing intrinsically photosensitive retinal ganglion cells, known as ipRGCs. Our current approach takes advantage of a diurnal mammalian model, the Nile grass rat, to test the novel hypothesis that melanopsin is critical for the expression of diurnal behavior and physiology, and is involved in masking responses to light. We will achieve this goal by injecting the immunotoxin anti-melanopsin-saporin intraocularly in grass rats and examining behavior following this experimental manipulation. Animals will be placed in various lighting conditions, including 12:12 light-dark conditions, and will be given pulses of light to test for effects of masking. We predict that controls will exhibit more general activity during the day, consistent with a diurnal species, and will exhibit increased activity following acute pulses of light. We predict that animals with the melanopsin toxin in the retina will be out of phase with controls in behavior following acute pulses of light, similar to animals with IGL lesions. Altogether, we are building a model to understand the mechanisms underlying the normal display of diurnal behavior, and we hope to add to this knowledge by examining how melanopsin contributes to the display of diurnal behavior in grass rats.

Related Products: Melanopsin-SAP (Cat. #IT-44)

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