James H. Fallon - US grants

During the coming year I plan to complete many of the immunocytochemistry projects that began in the past three years. This includes double labeling experiments on the forebrain distribution and connections of neurons containing CCK, EGF, dynorphin, enkephalin, dopamine, serotonin and norepinephrine. In addition, the physiological recordings from the SCN and lateral hypothalamus will continue along with neuroanatomical tracing in those hypothalamic regions with putative primary and secondary circadian oscillators. These psychological studies will include chronic multiple unit schedules, and the anatomical studies will focus on hodological and transmitter-specific connectional analyses with flourescent tracers, lectins and immunofluorescence technique.

The goal of this program is a physiological and anatomical analysis of the central neural mechanisms participating in circadian rhythm regulation. Circadian rhythms are an ubiquitous feature of organisms and in mammals, they appear to be genetically determined functions of endogenously generated oscillatory mechanisms. A number of these functions have profound effects on behavior and neuroendocrine regulation in the CNS. Previous studies have shown that the probable site of the "master clock" for circadian rhythm regulation in mammals resides in the suprachiasmatic nucleus in the hypothalamus. Visual input directly from the retina and indirectly from other visual centers are involved in synchronization of circadian rhythms. Very little is known as to the precise areas of the suprachiasmatic nucleus involved, the mechanisms involved, the interaction of secondary and primary synchronizers and oscillators involved and the anatomical connections necessary for the generation of circadian rhythms. The physiological studies proposed here include chronic multiple unit recordings in the suprachiasmatic nucleus and surrounding areas of the hypothalamus of the awake rat. Anatomical studies are on the afferent and efferent connections of the suprachiasmatic nucleus. These studies are designed in order to determine the precise nature and some basic mechanisms of circadian rhythm generation in the mammal. The anatomical studies will elucidate the differential connections of the areas invloved in primary (and secondary) oscillation.

The goal of this research is to determine how forebrain systems and neuropeptide-defined pathways control the neuroendocrine, autonomic and visceral neural systems in mammals. The short range goals of the research focus on three related issues: (1) How are circadian rhythms regulated in the central nervous systems? The effect of lighting schedule, feeding and drinking schedules, as well as physiological and pharmacological manipulations on the functions of central pacemakers in the albino rat will be studied. Longitudinal assays of overt motor activity, ingestive behaviors and neurophysiological activity will complement cross sectional analyses of opioid peptide levels, opiate receptor binding, metabolism, (by the 2-deoxyglucose method) and ultrastructural changes in hypothalamic regions thought to contain the primary (suprachiasmatic nucleus) and secondary (lateral hypothalamic area, e.g.) circadian pacemakers. The way the body responds to environmental and internal stress, disease states and drug therapy depends heavily on the functions of the circadian rhythm systems, therefore, understanding how these rhythms operate will increase our ability to maximize our own adaptation and survival. (2) In a related series of experiments, opioid peptide systems, especially the dynorphin-containing systems, are investigated for their role in the control of the neuroendocrine, autonomic and visceral neural systems. Preliminary studies suggest that the opioid neural systems are strategically placed to regulate not only circadian rhythms, but also other phylogenetically ancient motor systems related to eating, drinking, digestion, cardiovascular and respiratory control. The studies will aid in our understanding of how peptide systems control these important regulatory functions. The combined immunofluorescence and retrograde fluorescence tracing method will be used to determine connections of dynorphin-(and some enkephalin-) containing neurons in structures that innervate and control and peripheral sympathetic, parasympathetic, and neuroendocrine neural systems. (3) In the third group of experiments, "higher centers" that may regulate circadian rhythm generators and other motor neural systems will be investigated with new neuroanatomical methodologies. In particular, the efferents of the ventral pallidium to the hypothalamus, hypothalamus to brainstem, and convergence of retinal, ventral lateral geniculate nucleus, dorsal raphe and ventral pallidal inputs to hypothalamus will be studied with anterograde and retrograde techniques which overcome the problem of uptake of tracer by fibers of passage. These studies are important in that they will help elucidate the morphological substrates by which "higher" and "lower" brain centers integrate the classical motor systems, circadian rhythms, neuroendocrine systems, pituitary, and autonomic and visceral motor systems of the body.

The long term objectives of the proposed research are to elucidate the roles of the forebrain in the control of effector systems in the central nervous system of mammals. Chemically-defined pathways originating in the forebrain and terminating in neuroendocrine, autonomic and classical motor areas will be studied with combined morphological and immunohistochemical techniques. Twelve groups of experiments are designed to address three specific aims. The first specific aim addresses the hypothesis that the forebrain extrapyramidal motor systems control the neuroendocrine, autonomic and classical motor systems, in part, through the mesopontine tegmentum. Combined retrograde and anterograde tracing techniques are applied at the light and electron microscopic levels to determine if neurons in the mesopontine tegmentum which project to the hypothalamus, brainstem and spinal cord receive input from pallidal and peripallidal neurons of the forebrain motor and limbic systems. The second specific aim addresses the hypothesis that the mesopontine tegmental area which receives convergent forebrain inputs contains separate sets of transmitter-specific neurons which have stereospecific projections to neuroendocrine, autonomic, and classical motor areas. Multiple labeling immunohistochemical techniques are combined with retrograde tracing techniques to determine the neurochemical content and axon collateralization patterns of mesopontine projections to the hypothalamus, brainstem and spinal cord. The third specific aim addresses the hypothesis that the traditional hypophysiotrophic zones contain two functional types of neurons: one which controls the pituitary and a second which projects back to higher forebrain areas. Combined tract tracing and immunocytochemical techniques used at the light and electron microscopic levels will be used to determine both the chemistry and connections of different sets of defined hypothalamic neuronal systems. The proposed studies will enhance our understanding of the higher neuronal control of motor systems and will provide new information on how the forebrain, brainstem and hypothalamus integrate diverse motor systems in humans.