Another study will test the hypothesis that the functional SCN extends beyond the apparent cytoarchitectonic boundary in the rat and hamster. The role of the SCN in regulation of activity in areas innervated will be analyzed in slices in vitro . The hypothesis that specific groups of SCN efferents control specific circadian functions will be tested by lesion experiments. These properties indicate that circadian rhythms are generated and regulated by a neural system that includes photoreceptors and visual pathways, pacemakers, and efferent projections coupling the pacemakers to effector systems exhibiting circadian function. The intent of this study is to provide a detailed description of the primate, and particularly the human circadian system, including a characterization of the components of the system by their content of peptides and other neuroactive substances.
Controls receive placebo.
Using immunocytochemistry, the animals' brains are studied for regional serotonin content, for the retrograde transport of ligands from the terminal areas to the cell body of serotonin neurons, and for assessment of the number of serotonin neurons in the brain stem. If confirmed, this finding would argue that the effect of the drug, even at high doses, is to reduce serotonin content without producing a neurotoxic effect. Thus, defects in both GH secretion and GHR function result in growth failure and metabolic abnormalities. In order to begin addressing these hypotheses, investigators have now isolated the human GHR HV1 promoter of 16kb in length. The results of these studies will provide information on the structure and function of the GHR HV1 promoter, which will help determine the critical regions for future screening for the potential mutations associated with clinical GH insensitivity.