GPR3 and GPR6 have been previously linked to Alzheimer's and Parkinson's diseases. These receptors share about 35% of amino acid sequence with CB1 and CB2. CBD acts as an inverse agonist for these receptors as it has been shown in a β-arrestin2 recruitment assay (Laun & Song, 2017).

References:

Laun, A. S., & Song, Z.-H. (2017). GPR3 and GPR6, novel molecular targets for cannabidiol. Biochemical and Biophysical Research Communications, 490(1), 17-21. https://doi.org/10.1016/j.bbrc.2017.05.165