“The endocannabinoid system (ECS) is an important modulatory and potentially neuroprotective homeostatic system in the brain.

  We have investigated CB₁R availability in vivo in patients with AD…

 In conclusion, we found no in vivo evidence for a difference in CB₁R availability in AD compared to age-matched controls.

 Taken together with recently reported in vivo CB₁R changes in Parkinson’s and Huntington’s disease, these data suggest that the CB₁R is differentially involved in neurodegenerative disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/24189376