[34] Methods for the study of the biosynthesis of neuroendocrine peptides in vivo and in vitro

This chapter describes the techniques for studying the de novo biosynthesis of the neurohypophysial hormones oxytocin and vasopressin and their neurophysins, both to their posterior pituitary and brainstem terminal fields, and of the hypophysiotropic hormone luteinizing hormone-releasing hormone (LHRH). The chapter focuses on in vivo studies, with labeling studies, of neuroendocrine peptides and found that in vivo biosynthetic studies involving isotope administration to sites of cell bodies of origin of a peptide system of interest gives the highest levels of isotope incorporation. This approach has proved to be valuable to the study of other peptidergic systems in the central nervous system of the rat, such as the striatonigral substance P system, and the hypothalamic proopiomelanocortin system. In some cases, however, for example, to observe the directionality of the effects of feedback signals, especially steroid hormones, on neuroendocrine peptide biosynthesis, it is convenient to carry out studies in vitro. The chapter also describes the techniques for the study of luteinizing hormone-releasing hormone (LHRH) biosynthesis in primary dispersed cell cultures of perinatal rat hypothalami.