Cannabinoid-Receptor Agonists

Abstract

Endogenous and synthetic cannabinoids are known for their psychotic and analgesic potency upon systemic administration. Topical cannabinoid agonists are a new modality in chronic pruritus since a couple of years. Both cannabinoid receptors CB1 and CB2 were found to be expressed on cutaneous sensory nerve fibres, mast cells, and keratinocytes. The physiological role of cutaneous cannabinoids and their receptors is still under investigation, however, recent data suggest that they are involved in inflammation of especially allergic contact dermatitis, keratinocyte proliferation and are neurosensory as well (see Chapter 2 of Part I). It was demonstrated that during inflammation, CB1 expression in primary afferent neurons and transport to peripheral axons is increased and contributes thereby to enhanced antihyperalgesic efficacy of locally administered CB1 agonist.¹ In addition, injections of the CB2 agonist N-Palmitoylethanolamin (PEA) may inhibit experimental NGF-induced thermal hyperalgesia.² Experimentally induced pain, itch, and erythema could be reduced by application of a topical cannabinoid agonist.^3,4