Kv3.1 is a potassium channel that functions in action potential repolarisation in fast-firing neurons. Kv3.1 is not a classic Cannabinoid receptor but its activity is modulated by cannabinoids. Since cannabinoids have a physiological effect on Kv3.1 it is effectively a Cannabinoid receptor.
Kv3.1 channels are prominently expressed in brain (cerebellum > globus pallidus, subthalamic nucleus, substantia nigra > reticular thalamic nuclei, cortical and hippocampal interneurons > inferior colliculi, cochlear and vestibular nuclei), and in retinal ganglion cells.
Pertwee, R.G., Howlett, A.C., Abood, M.E., Alexander, S.P.H., Di Marzo, V., Elphick, M.R., Greasley, P.J., Hansen, H.S., Kunos, G., Mackie, K., et al. (2010). International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid receptors and their ligands: beyond CB₁ and CB₂. Pharmacol. Rev. 62, 588–631.