BEHAVIOR AND BRAIN IMAGING IN BABOONS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Very little is known in regard to the neurohumoral factors that regulative ingestive behaviors in primate species. In earlier work, we showed that increased salt intake behavior produced by salt depletion in the baboon requires functional brain angiotensin mechanism. However, components of the hypothalamic-pituitary-adrenal axis that are potent stimuli for salt and water intake in mice, rats, rabbits and ungulates do not have any effect on ingestive behaviors in baboons. The objective of this study is to develop a baboon preparation that will permit administration of neurohumoral factors to brain structures so we can observe activation of brain centers using fMRI technology. The initial steps require development of a non-ferrous metal cannula, system for administration of hormonal and neurotransmitter agonists and antagonists into brain CSF while collecting fMRI images for brain activation observations. An intravenous anesthetic protocol ahs been developed that permits sedation of baboons for periods of up to 3 hours wile collecting brain images. Using this procedure we have replicated in baboons a recent study we conducted in humans in which intravenous saline infusion was used to stimulate thirst while collecting PET images of brain activation. The areas of the baboon brain activated by hypertonic saline were identical to the brain centers activated in the human studies. We will explore several approaches for a non-metallic cannula system for implanting in the baboon lateral brain ventricle. The system will enable the collection of PET images of brain activation responses to stimuli applied directly to the brain.