Just after birth sensory pathways establish a representation of the periphery in the somatic sensory cortex. This map, maintained by sensory input throughout adulthood, is dynamically shaped by the location and density of the peripheral receptors. If a nerve is cut, or an arm is lost, the cortical representation of the body is updated. Map reorganization after injury to the body is however an extreme example of what no doubt occurs continuously. Until recently there was no method for examining this process of continual modification of the cortex. But now a few paradigms have been developed, one of them is the whisker pairing paradigm. When all whiskers except for two, on one side of the rat face are trimmed, the cortical representation of the rat's whiskers changes. Stimulation of the spared whiskers consistently evokes better responses in the somatosensory cortex than does stimulation of the trimmed whiskers. The studies proposed here aim to discover the mechanisms underlying this reorganization of the cortex. The neurotransmitters acetylcholine and norepinephrine are in a position to influence the production of whisker pairing plasticity. One method for examining their role in the changes associated with whisker pairing paradigm is to remove them from the somatosensory cortex before any reorganization of the cortex has occurred. Their role in whisker pairing induced reorganization of the cortex can then be examined. Novel immunotoxins have been developed for removing acetylcholine and norepinephrine from the brain. In this study we propose to use these toxins, individually at first, then together and examine whether the reorganization of cortical maps is still possible.
