A direct retinal projection to the dorsal raphe nucleus in the rat

Brain Res. 1994 Jan 28;635(1-2):159-68. doi: 10.1016/0006-8993(94)91435-4.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Afferent Pathways / physiology
  • Animals
  • Male
  • Neural Pathways / physiology
  • Periaqueductal Gray / physiology
  • Raphe Nuclei / physiology*
  • Rats
  • Rats, Wistar
  • Retina / physiology*