OVERALL OBJECTIVES: Our laboratory is devoted to the study of functional regeneration in the mammalian spinal cord. The model system under study is the spinal cord of the adult cat. Specifically, this project investigates the possibility that spindle group II afferents may generate new functional connections with spinal motoneurons. Synaptic sites are made available on these motoneurons as a consequence of temporary ischemia of the spinal cord, eliminating interneurons normally occupying about 95 percent of all synaptic sites on motoneurons. The fundamental question asked is whether spindle group II afferents sprout to form new functional contacts in response to the presence of newly-available synaptic sites, in the post-ischemic spinal cord. The existence of new group II-motoneuron synapses would be suggested by the presence of single fiber spindle group II EPSPs of unusually large magnitude (greater than 100 uV) or in an unusually large number of motoneurons (the percentage will depend upon the conduction velocity of the particular afferent). In addition, a number of other important questions will be asked concerning neuronal function in the post-traumatic cord: Are single fiber EPSPs then different in configuration (indicative of altered synaptic location on the soma-dendritic membrance)? Are different types of motoneurons contacted? Are denervated mononeurons more or less excitable (rheobase, repetitive firing properties)?
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