a flowering plant from which more than 400 compounds have been identified.
Delta- 9- tetrahydrocannabinol (??- THC) is the
most potent psychoactive compound identified. Other potent cannabinoids include
??- THC, cannabidiol and cannabinol (The
health effects of cannabis and cannabinoids: the current state of evidence and
recommendations for research, 2017). ??-
THC acts within the brain by binding to cannabinoid receptors, CB1 and CB2.
CB1 and CB2
receptors are G- protein- coupled receptors known to inhibit the action of
adenylate cyclase and activate mitogen- activated- protein kinase. CB1
receptors are prevalent at the terminals of central and peripheral neurons of the
cerebral cortex, hippocampus, lateral caudate- putamen, substantia nigra pars
reticulata, globus pallidus, entopeduncular nucleus and the molecular layer of
the cerebellum. They are also
concentrated in the pain pathways of the brain and spinal cord. Their high
concentration in the aforementioned areas may account for the ability of CB1
receptor agonists such as ??- THC to impair cognition and memory as well as
motor function and anticonception. CB2 receptors are mainly present in immune
cells including lymphocytes, macrophages, mast cells, microglial cells, killer
cells and peripheral mononuclear cells.
The body produces
natural chemicals -endocannabinoids- which together with their receptors comprise
the endocannabinoid system. These endocannabinoids -N- arachidonoyl-
ethanolamine (anandamide) and 2- arachidonoyl glycerol- function as retrograde
synaptic messengers. Increasing calcium ions in post synaptic neurons results
in the release of endocannabinoids such as 2- arachidonoyl- glycerol. This
results in the activation of presynaptic CB1 receptors which leads to the
inhibition of neurotransmitters such as glutamate and GABA. Endocannabinoids therefore
help to maintain homeostasis by preventing excessive neuronal activity in the
central nervous system.
regulates emotions such as fear and anxiety (amygdala), learning and memory
(hippocampus), appetite and sexual behavior (hypothalamus), motor coordination
and balance (cerebellum), complex thinking, feeling and movement (neocortex)
and motivation and reward (nucleus accumbens. Cannabinoids such as ??- THC can
therefore affect emotions, learning and memory, appetite and sexual behavior,
motor coordination and balance, movement and motivation and reward by binding
to the CBD receptors in the brain.