Advances in neurobiology: an introduction

The following five manuscripts showcase the work presented at the symposium ‘‘Advances in Neurobiology’’ at the Annual Meeting for the Society for Integrative and Comparative Biology held in San Antonio, Texas, January 2–6, 2008. The symposium utilized a unique format, namely a pairing of a senior investigator with a junior investigator from the same laboratory. In this way, the symposium provided an opportunity for junior scientists in the field to begin to receive recognition for their efforts relatively early in their professional development. The symposium emphasized the diversity of animal models in which control (through both excitation and inhibition) of secretion of the hypothalamic peptide gonadotropin releasing hormone (GnRH) and its derivatives contributes to sexual reproduction and behavior. The classic GnRH-I is a well recognized decapeptide hormone critical for sexual reproduction, and the advent of transgenic mouse models has allowed for investigations of electrophysiological output in single GnRH neurons. Drs. Roberts and Suter focused on their electrophysiological studies of rodent models and demonstrated how contemporary computational approaches can expand our understanding of the control of output of GnRH neurons. The team of Drs. Ubuka and Bentley presented their provocative findings of the long-reputed gonadotropin inhibiting hormone (GnIH). The GnIH family of peptides is derived from a single precursor molecule as in the processing of other neuropeptide precursors. The GnIH peptides inhibit both directly and indirectly the synthesis and the release of GnRH-I and GnRH-II peptides. Moreover, if what is known about the GnRH-I peptide can be directly applied to the GnIH family, it is possible that metabolites of GnIH could have further physiological actions (Roberts et al. 2007). Drs. Tello and Sherwood extended the discussion to the diversity of GnRH receptors in zebra fish, the multiple locations where GnRH receptors are expressed, as well as the multiple physiological functions the GnRH peptide may serve in these different locations. As such, the GnRH peptide family graphically embodies the emerging view of the diversity of peptides from the same parent family and the functional repertoire the peptide and its derivatives serve in the central nervous system. In an increasing number of vertebrate species, additional forms of the GnRH peptide have been identified. At least two forms of the GnRH peptide exist in humans and in nonhuman primates (GnRH-I and -II). Previously, such peptide variants were considered to be vestigial or nonfunctional forms of the existing parent peptides. As demonstrated by Drs. Rissman and Schider in their novel animal model, the musk shrew, the GnRH peptide II appears to provide a critical link between energy balance and sexual reproduction. Thus, it is likely the GnRH-II peptide will emerge as a pivotal player in coordinating reproduction with nutritional status. Drs. Desjardins and Fernald presented their provocative work with neurons containing the GnRH-I peptide and its regulation within social contexts. There is a rapid increase in neuronal size of GnRH neurons during the transition from nonterritorial to territorial status. Moreover, this social cue leads to global alterations such as gene expression and behavior. Thus, in their model system, a social cue is directly related to a change in the brain in a region with functional significance. As such, it appears that the neurons containing the GnRH-I peptide may provide an essential link between reproduction and social status.