The regulation and physiological management of feeding behaviour, appetite and fullness in humans, and many other multicellular organisms, is governed by the pathways involved in the Endocannabinoid system (ECS). This complex system comprises lipid endocannabinoids e.g. Anandamide (AEA), that bind to cannabinoid receptors (e.g. CB1 and CB2), together with the enzymes involved in cannabinoid generation and hydrolysis. The ECS can also be stimulated by the plant cannabinoids (phytocannabinoids) such as Δ9-tetrahydrocannabidiol (Δ9-THC) and cannabidiol (CBD) which are found in Cannabis sativa.

This study examined the effects exogenous of AEA and CBD on prey ingestion and food vacuole formation in the ciliate Tetrahymena pyriformis when feeding on an indigestible fluorescent cyanobacterium Synechococcus. Both AEA and CBD affected the ciliate feeding by inducing a lag; AEA having a shorter lag (ca. 36 min) in comparison to CBD (ca. 60 min). When ingestion resumed, AEA-treated cells fed at the same rate as the Control cells whereas CBD-treated cells had elevated ingestion rates (hyperphagia). The mechanism behind this is currently unknown but it does not appear to involve a cessation of food
vacuole trafficking and defecation. It was also considered unlikely to be due to vacuole membrane recycling and the formation of phagocytic cups as the cellular machinery for this is very similar to that required for vacuole trafficking, which is unaffected by AEA and CBD. The study therefore hypothesised that: AEA and CBD completely stops prey capture but that pre-existing vacuoles are trafficked and defecated as normal and membrane is recycled to the cytostome where it accumulates. A lag of 60 min would allow the accumulation of more
membrane than a 30 min lag and is the possible reason as to why ingestion rates after the former are higher.

This study provides a basis for future research into the effects of CBD and AEA on the feeding capture processes of protists as well as their potential targets. Since protists do not possess the usual cannabinoid receptors associated with the human ECS future work might elucidate the ancestral targets of these cannabinoids together with their function in single cells.