The endocannabinoid system has been studied using genetic and pharmacological methods.
The endocannabinoid system is a biological system composed of endocannabinoids, which are endogenous lipid-based retrograde neurotransmitters that bind to cannabinoid receptors, and cannabinoid receptor proteins that are expressed throughout the mammalian central nervous system (including the brain) and peripheral nervous system.
The endocannabinoid system is involved in regulating a variety of physiological and cognitive processes including fertility, pregnancy during pre- and postnatal development, appetite, pain-sensation, mood, and memory, and in mediating the pharmacological effects of cannabis.
The endocannabinoid system is also involved in mediating some of the physiological and cognitive effects of voluntary physical exercise in humans and other animals, such as contributing to exercise-induced euphoria as well as modulating locomotor activity and motivational salience for rewards.
In humans, the plasma concentration of certain endocannabinoids has been found to rise during physical activity. Since endocannabinoids can effectively penetrate the blood-brain barrier, it has been suggested that anandamide, along with other euphoriant neurochemicals, contributes to the development of exercise-induced euphoria in humans, a state colloquially referred to as a runner's high.