Self-Administration of an Endogenous Cannabinoid 2-Arachidonoylglycerol in Experimentally Naïve Rats

A recent study by Dr. Maria Antonietta De Luca demonstrated intravenous (IV) selfadministration responding (nose-poking) of an endogenous compound in an experimentally naïve, adult rat species [1]. Surprisingly, response-dependent changes of visual stimulus were not presented in the study when the compound was injected. This finding is very unique since there is few if any endogenous compounds that have been reported to maintain self-administration responding above vehicle levels through an IV route of administration (i.e. not intracranial self-injections) in rodent species. Further, it is also likely that a phytocannabinoid (−)-trans-Δ9-tetrahydrocannabinol (Δ9-THC, Figure 1), a primary psychoactive constituent in marijuana, is not an effective reinforcer in rat [2,3] and rhesus monkey species [4-6] relative to standard drugs of abuse [7].