Direct visual and circadian pathways target neuroendocrine cells in primates.
The effect of light on neuroendocrine functions is thought to be mediated through retinal inputs to the circadian pacemaker, the hypothalamic suprachiasmatic nucleus (SCN). The present studies were conducted to provide experimental evidence for this signaling modality in non-human primates. In the St. Kitts vervet monkey, anterograde tracing of SCN efferents revealed a monosynaptic pathway between the circadian clock and hypothalamic neurons producing luteinizing hormone-releasing hormone (LHRH). Using a variety of tracing techniques, direct retinal input was found to be abundant in the SCN and in other hypothalamic sites. Strikingly, in hypothalamic areas other than the SCN, primary visual afferents established direct contacts with neuroendocrine cells including those producing LHRH and dopamine, neurons that are the hypothalamic regulators of pituitary gonadotrops and prolactin. Thus, our data reveal for the first time in primates that light stimuli can reach the hypothalamo-pituitary-gonadal axis, directly providing a pathway independent of but parallel to that of the circadian clock for the photic modulation of hormone release.
Abizaid
Alfonso
A
Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06510, USA.
Horvath
Balazs
B
Keefe
David L
DL
Leranth
Csaba
C
Horvath
Tamas L
TL
D000818:Animals; D002772:Cholera Toxin / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism; D004525:Efferent Pathways / Q000166:cytology / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D009474:Neurons / Q000145:classification / Q000378:metabolism*; D009490:Neurosecretory Systems / Q000166:cytology*; D010835:Phytohemagglutinins / Q000378:metabolism; D011323:Primates; D013493:Suprachiasmatic Nucleus / Q000166:cytology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism; D014795:Visual Pathways / Q000166:cytology*
D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants; D007987:Gonadotropin-Releasing Hormone; D014660:Vasoactive Intestinal Peptide; D002772:Cholera Toxin; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine