Behavioral methods in cannabinoid research

In the absence of any specific behavioral assay for cannabinoids or endocannabinoids, a cannabinoid-induced profile in a series of four in vivo assays in mice is most commonly used to assess a specific cannabinoid activity at the behavioral level. Thus, when a given compound produces motor depression in an open field, catalepsy on an elevated ring, analgesia on a hot plate, as well as hypothermia, cannabinoid CB1 receptor activation is assumed, although exceptions are possible. The full cannabinoid profile, however, includes for example ataxia in dogs and discrimination learning in rats. In view of (1) the addictive/reward potential of cannabis and the cannabinoids and (2) the multiple roles of the endocannabinoid physiological control system (EPCS) in behavioral functions, including memory, emotionality, and feeding, a number of behavioral techniques have been used to assess the effects of cannabinoids in these functions. In this chapter we will describe the tetrad of cannabinoid-induced effects as well as a series of behavioral assays used in the behavioral pharmacology of marijuana-cannabinoid research. Since the EPCS plays an important role in the developing organism, methods used in the assessment of physical and behavioral development will also be discussed. The techniques include the tetrad, drug discrimination, self-stimulation and self-administration, conditioned place preference/aversion, the plus-maze, chronic mild stress (CMS), ultrasonic vocalizations, cognitive behaviors, and developmental assessment in mouse (and rat) pups.