Interestingly, mRNA of both orexin receptors, OX1R and OX2R, has been found exclusively in the AM (Marcus et al. 2001), while immunohistochemical detection conducted by Hervieu et al. (2001) showed that OX1R is present in the AD and AV in a density ranging from sparse to extensive. Here, HCRTR1 is linked to Alzheimer disease.