1987 Volume 8 Issue 4 Pages 253-262
Interactions of retinal projections and VIP-like immunoreactive neurons in the suprachiasmatic nucleus (SCN) of the rat were investigated by horseradish peroxidase (HRP)-histochemical, peptide immunocytochemical, electron microscopic, and morphometric analyses. HRP-filled retinal fibers were detected in the contralateral and ipsilateral part of the ventrolateral part of SCN. Neurons immunoreactive to vasoactive intestinal peptide (VIP), peptide histidine isoleucine amide (PHI), and gastrin releasing peptide (GRP) showed the same distribution as the HRP-filled retinal projections in the intermediate and caudal level of SCN. In immunoelectron microscopy, non-immunoreactive neuropil elements made synaptic contact with VIP-immunoreactive neurons. Degenerating electron microscopic study showed that retinal axon terminals engulfed dendritic spines in SCN. The technique of immunocytochemistry combined with morphometric analysis by color image analyzer revealed that VIP-immunoreactive dots were increased in number 7 days after bilateral enucleation. These results strongly suggest the close interaction between retinal afferents and VIP-containing neurons in SCN.
