Fig. 9.

Schematic illustration of the relationship among visual, circadian, and neuroendocrine cells in the hypothalamus. Retinal efferents (green) innervate IGL neurons (filled blue circles) that project to the hypothalamus (blue lines) and innervate different populations of neurons. Subpopulations of these neurons in the MPO, periventricular area (Pe), and arcuate nucleus (ARC) contain dopamine (DA) and/or are neuroendocrine (ne) revealed by systemic fluorogold labeling. A population of neurochemically unidentified (?) neuroendocrine cells were also found to receive IGL efferents. Neurons of the SCN (filled red circles) receive retinal (green) and IGL efferents (blue) and innervate (red lines) the same population of hypothalamic cells as IGL processes. V, Third ventricle; oc, optic chiasm; ot, optic tract. Dashed black lines indicate projections to fenestrated capillaries.