A direct retinal projection to the dorsal raphe nucleus in the rat.
A direct projection from the retina to the dorsal raphe nucleus at the pontomesencephalic junction was demonstrated with both antero- and retrograde tracing techniques in the rat. Following intravitreous injections of choleratoxin subunit B (CTB), horseradish peroxidase (HRP) and CTB-conjugated HRP, varicose fibers were labeled in the lateral region of the dorsal raphe nucleus, predominantly contralateral to the injection. Many of these labeled fibers were intermingled with serotonin-immunoreactive neurons, but some fibers were also found further laterally, beyond the boundary of dorsal raphe nucleus but within the periaqueductal gray. Following injections of the retrograde tracers Fluoro-Gold and CTB into the dorsal raphe nucleus and adjacent periaqueductal gray (without contamination of previously known targets of retinal projections), a small population of ganglion cells was labeled in the retina. These data provide evidence for the existence of a direct retinal projection to the lateral region of the dorsal raphe nucleus and the adjacent mesopontine periaqueductal gray in the rat. This projection may have a role in sensorimotor coordination and the regulation of circadian rhythm as well as sleep and wakefulness.
Shen
H
H
Department of Anatomy and Neurobiology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Semba
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K
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D010487:Periaqueductal Gray / Q000502:physiology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000502:physiology*