The main goal of this project is to determine what role the neurotransmitter nitric oxide plays in use dependent plasiticity. Previous data has shown that the rat somatosensory cortex exhibits plasticity in its metaboloic response to stimulation. The metabolic representation in the cortex of a spared facial vibrissae is expanded following denervation of the surrounding vibrissae Although this metabolic expansion is most dramatic following neonatal denervation, there is still significantpasticity when the denervation occurs in the adult animal. Using autoradiography we are further investigating this metabolic plasticity and are undertaking studies to determine if the magnitude of the expanded metabolic response to virbrissal stimulation is altered following chronic treatment with an inhibitor of nitric oxide synthase. Measurements of local cerebral glucose utilization with C/2-deoxyglucose during stimulation of the virissae have been made in rats that have undergone vibrissae deneervation. These studies procued a large number of autoradiograms in which computerized image analysis is essential. Each animal yields 60-80 relevant secions, and a typical protocol involves 18-24 animals. In each section the distribution of the deoxyglucose in the somatosensory cortex as a result of vibrissae stimulation is being analyzed using BRAIN. This involves registration of the autoradiographic image with the same section that has been stained for cytochrome oxidase so as to insure that the appropriate cortical region is analyzed. Initial data indicates that nitric oxide does attenuate the normally enlarged metabolic representation contralateral to the denerated vibrissae.