Recently developed electroanalytical techniques are to be used to provide a new understanding of the static and dynamic functioning of catecholamines and related substances in small animal brains. Microelectrodes, improved in selectivity and quantitative response, will be used to upgrade the already reliable in vivo electrochemistry methodology. This technique measure changes in concentration of catecholamines and related substances in brain extracellular fluid. Using an inexpensive microprocessor to control simultaneous multiple site electrochemical recording, we will begin mapping functional chemical changes in brain areas following sensory and environmental stimulation of unanesthetized, unrestrained rats. High sensitivity liquid chromatography with electrochemical detection in conjunction with punching techniques has uncovered unusual concentration gradients and strong chemical lateralization (left-right hemispheric differences) of catecholamines in discrete rat brain areas. We will provide detailed quantitative mapping of these distribution patterns for catecholamines and ascorbate in rat cortex, thalamus and other inner core structures. Neurotransmitter concentration profiles and, especially, hemispheric differences are practically uncharted in small animal brains. The biogenic amine distribution patterns may also help explain dynamic chemical responses seen with the in vivo electrodes.