MORPHOLOGICAL SURVEY OF THE SUPRACHIASMATIC NUCLEUS IN SLICE CULTURE USING ROLLER TUBE METHOD .2. PEPTIDERGIC NEURONS

The expression of peptidergic traits was analyzed in the slice culture of the suprachiasmatic nucleus (SCN) by the roller tube technique. Si nce the slice thickness was one to three cell layers after three weeks in vitro, the in situ hybridization and immunocytochemistry could be applied directly to the slices without further cutting. We found the e xpression of peptides and their messenger RNAs in neurons of the neuro nal zone occurring in a topographic distinct pattern; vasopressin (AVP ) containing; neurons in the dorsomedial part near the ependymal zone and vasoactive intestinal peptide (VIP) containing neurons in the vent rolateral part of the neuronal zone. VIP-neurons aligned on the border of the neuronal zone and dispersed cell zone, projected fibers in the fixed directions; the thick process to the center of the neuronal zon e, and the thin process to the opposite direction. For somatostatin (S OM) expressing neurons, two types of SOM mRNA containing cells were de tected; the larger cells expressing a stronger signal located in and n ear the ependymal layer, and smaller cells expressing a weaker signal in the dorsomedial part of the neuronal zone. The larger SOM neurons i n vitro correspond to the periventricular SOM neurons in vivo, the sma ller SOM neurons in vitro correspond to the SOM neurons in the SCN in vivo. Rhythmic AVP release occuring in vivo were also recorded in the medium of the slice culture system by enzyme immunoassay. The similari ty of the distribution pattern of VIP, AVP and SOM neurons in vitro an d in vivo, and persistent rhythmic release of AVP in vitro, suggest th at the peptidergic neurons develop with the original neuronal network being preserved and secrete peptides as they do in vivo.