δ-opioid receptors are primarily sensitive to opioids and enkephalins. δ-opioid receptors are not classic Cannabinoid receptors but their activity is modulated by cannabinoids. Since cannabinoids have a physiological effect on δ-opioid receptors they are effectively Cannabinoid receptors.
δ-opioid receptors are widely distributed throughout the CNS, most prominant expression in the forebrain regions: Caudate putamen, nucleus accumbens, amygdala, pontine nucleus, olfactory bulb, olfactory tubercle > interpeduncular nucleus, cortex (most dense in layers II-III and V-VI) > thalamus, hypothalamus, stria terminalis, hippocampus, globus pallidus, preoptic area, colliculi. Virtually no binding in the periaqueductal grey and raphe nuclei.
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.