Synaptogenesis in the rat suprachiasmatic nucleus: a light microscopic immunocytochemical survey.

MabQ155, a monoclonal antibody against synaptophysin, has been used to conduct a light microscopic survey of synaptogenesis in the suprachiasmatic nucleus of the perinatal rat. Synaptophysin is an integral component of synaptic vesicle membranes which is expressed in growth cones and growth cone filopodia as well as in mature synapses. With the light microscope, mabQ155 immunoreactivity in growth cones can be distinguished from that in presynaptic terminals on the basis of the size of immunoreactive puncta. The current study presents a qualitative and quantitative analysis of synaptogenesis from the day of birth (P0) to postnatal day 10 (P10). In our quantitative analysis we have used daily intervals during the first postnatal week, distinguished between growth cones and presynaptic terminals, and divided the suprachiasmatic nucleus into sampling regions that are related to the progress of synaptogenesis. Our data demonstrate regional differences in synaptogenesis within the suprachiasmatic nucleus (SCN), document the temporal progression from the penetration of growth cones to the appearance of mature synapses, and provide information about gradients of synaptogenesis in the nucleus during development.