Neurodegenerative disorders result from a wide variety of toxic, traumatic and genetic insults which lead to the degeneration and death of neurons. In sharp contrast, adult spinal motor neuron populations not only completely survive traumatic injury (axotomy) that produces irreversible loss in other neuronal populations, their axons functionally reinnervate their targets. A better understanding of the largely unknown, cellular and molecular mechanisms responsible for this impressive injury response obviously would be of great potential benefit in the struggle to design effective treatments for neurodegenerative disorders. We hypothesize, and several independent lines of indirect evidence suggest, that CNTF receptor a (CNTFRa) makes a critical contribution to the survival and regeneration of adult spinal motor neurons following axotomy. However, studies to date have not directly determined: 1) where, when and to what extent CNTFRa protein is expressed following such a lesion and is therefore potentially active (Specific Aim 1); 2) what CNTFRa signal transduction events are induced by the lesion (Specific Aim 2); and 3) what role(s) CNTFRa plays in the survival and regeneration of the injured neurons (Specific Aim 3). We will use the sciatic nerve lesion model and immunohistochemically map lesion-induced changes in CNTFRa expression at a subcellular level of resolution with our anti- CNTFRa antibodies and confirm our findings through in situ hybridization, northern and western blots (Specific Aim 1). Various lesion-induced, "candidate" CNTFRa signal transduction events will be characterized with immunohistochemistry, in situ hybridization or retrograde transport procedures and identified as CNTFRa dependent by inhibition of in vivo CNTFRA function with function blocking antibodies, a mutant CNTF that acts as an antagonist, and antisense DNA (Specific Aim 2). CNTFRa's role in survival, neurotransmitter phenotype and axonal regeneration following lesion similarly will be determined by measuring how these properties are influenced by inhibition of in vivo CNTFRa function (Specific aim 3). In addition to greatly expanding the current understanding of CNTFRa's role in spinal motor neuron survival and regeneration, the proposed experiments will constitute the first direct in vivo examination of adult CNTFRa function.