Cannabis sativa, commonly known as pot or marijuana, is considered to be the most widely used drug by teenagers in the United States and Europe. Marijuana is composed of 60 cannabinoids, which are psychoactive compounds found in the cannabis plant (Steinherz and Vissing, 1997-1998; US DOJ Editors, 2014).
Since it is fat-soluble, marijuana and its metabolites can easily go through the blood-brain barrier which controls the path of all substances in the brain. Delta-9-THC which is the compound that induces the “high” feeling when marijuana is inhaled passes through lipid-rich tissues of the body until it reaches the brain. The compound binds with cannabinoid receptors, which control thought processes, concentration, memory and coordinated movement (National Institute of Health Editors). Its direct effects on the brain are short-term memory, coordination and locomotion disorders, absentmindedness and lethargy (Steinherz and Vissing, 1997-1998; US DOJ Editors, 2014).
The activity of neurons in the hippocampus is decreased since marijuana greatly affects the memory (National Institute of Heath Editors, 2016). The most prevalent neurotransmitters in the brain are glutamate and GABA (gamma-aminobutyric acid). Half of the brain utilizes glutamate, which is excitatory in function, while GABA, which is inhibitory, has 30-40% utilization. Processes such as the brain’s excitation are controlled by theses neurotransmitters. Most abused drugs affect either glutamate or GABA functions since they release tranquilizing or stimulating elements in the brain (Genetic Science Learning Center, 2015). Pre-synaptic glutamate release is suppressed by endocannabinoids present in marijuana, while pre-synaptic GABA release is inhibited by the same compounds. Cannabinoid agonists like delta-9-THC cause long-term synaptic plasticity resulting in persistent increase or weakening in synaptic signals lasting for long periods of time (Fratta and Fattore, 2013).
Aside from the action of neurotransmitters in the brain, certain genes have been found to perform a role in drug addiction. Through the help of model organisms like the mice, genes that play a role in addiction have counterpart genes in humans. For instance, if the mice do not have the cannabinoid receptor gene Cnr1, they are less responsive to morphine (Genetic Science Learning Center, 2015). Cannabinoid receptors (CB1Rs) are subject to desensitization and down regulation which lead to long-term consequences of cannabinoid exposure but aside from this, gene expression and intracellular signaling cascades are also significant in drug addiction. Molecular targets have been determined with regard to chronic cannabinoid action in which region-specific changes rely on age of exposure and sex (Fratta and Fattore, 2013).
Indeed, marijuana has adverse effects on people due to the drug’s action on neurotransmitters in the brain. Moreover, genes were determined to have an effect as well on marijuana addiction.
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