Anandamide Receptors: Role in Motor Neuron Protection

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DESCRIPTION (provided by applicant): Significant advances are being made towards understanding the genetic basis for ALS as well as the mechanistic and molecular pathways mediating progression of the sporadic forms of the disease; however, effective pharmacotherapy remains elusive. Two of the primary theories for the development and progression of ALS suggests that motor neuron degeneration and death is due to susceptibility to excitotoxicity and oxidative damage. The experimental system described within extends current ALS paradigms, proposing that excitotoxicity and oxidative damage may result from presumed loss of modulatory control and that stimulating the endogenous anandamide/CB receptors may provide a mimic or substitution for that modulation. The endogenous anandamide/CB receptor system effectively modulates glutamatergic neurotransmission and toxicity. We have found anandamide/CB receptors in brain areas associated with motor control, including their presence in motor neurons. We demonstrate that anandamide/CB receptor agonists attenuate excitotoxicity in spinal cord cultures. In addition, CB receptor agonists are antioxidants that may work synergistically on both hypothesized pathogenic mechanisms. These studies have been made possible by our recent cloning and characterization of anandamide receptors, the discovery of endogenous compounds that act via these receptors (anandamides), and the development of novel pharmacological tools that allow us to monitor the effects produced by activation of anandamide receptors. In the first specific aim, we will identify, localize and characterize endogenous anandamide/CB receptors present in the mouse spinal cord. We hypothesize that both glutamate receptors and anandamide receptors co-localize in mouse spinal cord motor neurons, providing an anatomical rationale for neuroprotective effects in vitro and in vivo. In the second specific aim, we will extend our preliminary findings on attenuation of excitotoxicity in spinal cord cultures and define the role of anandamide receptor agonists in modulating neurotoxicity in motor neurons from mouse spinal cord. We will study the effects of anandamide/CB receptor modulation in two paradigms producing neurotoxicity: excitotoxicity produced by direct application of excitotoxins; and toxicity produced by oxidative damage. These paradigms will be conducted in normal mice as well as ALS model mice (transgenic mice carrying a mutant human SOD 1 gene). The relative role of the CB, receptor in neuroprotection will be evaluated by examining agonist effects in CBr knockout mice. The system proposed will allow us to experimentally manipulate major components of the complex motor neuron environment and thereby test specific hypotheses of ALS disease development and possible ameliorating therapies. The anandamide/CB receptor system offers a potential cellular mechanism by which both antioxidant and anti-excitotoxic effects might be achieved simultaneously, with the possibility of a more substantial therapeutic effect.