Visual Neuroscience



Melanopsin and non-melanopsin expressing retinal ganglion cells innervate the hypothalamic suprachiasmatic nucleus


PATRICIA J.  SOLLARS  a1 , CYNTHIA A.  SMERASKI  a1 , JESSICA D.  KAUFMAN  a1 , MALCOLM D.  OGILVIE  a1 , IGNACIO  PROVENCIO  a2 and GARY E.  PICKARD  a1 c1
a1 Department of Biomedical Sciences, Colorado State University, Fort Collins
a2 Department of Anatomy, Physiology, and Genetics, Uniformed Services, University of the Health Sciences, Bethesda

Article author query
sollars pj   [Google Scholar] 
smeraski ca   [Google Scholar] 
kaufman jd   [Google Scholar] 
ogilvie md   [Google Scholar] 
provencio i   [Google Scholar] 
pickard ge   [Google Scholar] 
 

Abstract

Retinal input to the hypothalamic suprachiasmatic nucleus (SCN) synchronizes the SCN circadian oscillator to the external day/night cycle. Retinal ganglion cells that innervate the SCN via the retinohypothalamic tract are intrinsically light sensitive and express melanopsin. In this study, we provide data indicating that not all SCN-projecting retinal ganglion cells express melanopsin. To determine the proportion of ganglion cells afferent to the SCN that express melanopsin, ganglion cells were labeled following transsynaptic retrograde transport of a recombinant of the Bartha strain of pseudorabies virus (PRV152) constructed to express the enhanced green fluorescent protein (EGFP). PRV152 injected into the anterior chamber of the eye retrogradely infects four retinorecipient nuclei in the brain via autonomic circuits to the eye, resulting in transneuronally labeled ganglion cells in the contralateral retina 96 h after intraocular infection. In animals with large bilateral lesions of the lateral geniculate body/optic tract, ganglion cells labeled with PRV152 are retrogradely infected from only the SCN. In these animals, most PRV152-infected ganglion cells were immunoreactive for melanopsin. However, a significant percentage (10–20%) of EGFP-labeled ganglion cells did not express melanopsin. These data suggest that in addition to the intrinsically light-sensitive melanopsin-expressing ganglion cells, conventional ganglion cells also innervate the SCN. Thus, it appears that the rod/cone system of photoreceptors may provide signals to the SCN circadian system independent of intrinsically light-sensitive melanopsin ganglion cells.

(Received April 14 2003)
(Accepted September 2 2003)


Key Words: Melanopsin; Suprachiasmatic nucleus; Retinal ganglion cell; Circadian rhythm; Retinohypothalamic tract; Pseudorabies virus.

Correspondence:
c1 Address correspondence and reprint requests to: Gary E. Pickard, Department of Biomedical Sciences, Section of Anatomy and Neurobiology, Colorado State University, Fort Collins, CO 80523-1670, USA. E-mail: gpickard@lamar.colostate.edu