Strategies for cell biological studies in oxytocinergic neurons

Hypothalamic magnocellular neurons expressing the neurohypophysial peptides, oxytocin (OT) and vasopressin (AVP), have historically served as valuable models for cell biological studies of peptidergic neurons. This is because of the relative ease with which the perikarya, axons, and nerve terminals of these cells can be isolated for anatomical, biochemical, and physiological analysis. A popular strategy is to harness the regulatory elements in the OT and AVP genes in order to target specific molecules to these cells in vivo, so as to elucidate various cell biological issues, e.g., pacemaker, prohormone processing, axonal transport, and secretion mechanisms. The peptide genes are good sources for regulatory controls since they are relatively abundantly and specifically expressed in these neurons in the CNS. The major problem has been to identify the critical regulatory elements in these genes which are responsible for the cell-specific expression. Recent transgenic studies have implicated various 3'-untranslated nucleotide sequence regions in the OT and AVP genes which appear to contain these regulatory elements. A structural analysis of these regions in the mouse genes will be discussed. A second problem has been the availability of appropriate model systems to test constructs for "cell-specific" expression. Transgenic mice have been effective models in this regard but are costly and labor-intensive. An alternative approach using biolistic techniques to transfect slice-explants containing the primary OT and AVP neurons in culture will be described.