Marijuana, also known as cannabis, among other
names, is a preparation of the Cannabis sativa plant – the hemp plant, intended for recreational
and medicinal uses. Marijuana can be consumed by smoking, inhaling, or mixing with food.
The main psychoactive chemical in marijuana, responsible for most of the intoxicating effects
sought by recreational users, is delta-9-tetrahydro-cannabinol, or THC. The Cannabis plant preparation also
contains at least 65 other compounds that are chemically related to THC, called cannabinoids.
THC is chemically similar to a class of substances found naturally in our nervous system called
endogenous cannabinoids, or endocannabinoids, of which anandamide is best known so far.
The endocannabinoids are part of a newly discovered system named the Endocannabinoid system, or
ECS. A human brain contains billions of nerve cells,
or neurons, which communicate via chemical messages, or neurotransmitters. When a neuron
is sufficiently stimulated, a neurotransmitter is released into the synaptic cleft – a space
between neurons. The neurotransmitter then binds to a receptor on a neighboring neuron,
generating a signal in it, thereby transmitting the information to that neuron. Neuron communication
is essential to all brain activities. The ECS acts as a modulator of this neurotransmission.
When the postsynaptic neuron is activated, endocannabinoids are produced, released, and
travel back to the presynaptic neuron where they activate cannabinoid receptors. By doing
so, they control what happens next when the presynaptic cell is again stimulated. The
general effect is a DECREASE in the release of neurotransmitters such as GABA or glutamate.
In other words, the ECS acts as a “brake”, SLOWING down neuronal activities, preventing
neurons from excessive firing. Some examples of ECS functions include:
– Pain modulation: cannabinoids SUPPRESS pain signal processing, producing pain relief effects.
– Stress and anxiety reduction: while response to stressful stimuli is necessary for an organism
to react appropriately to a stressor, CHRONIC stress may be harmful. The ECS plays a role
in the habituation of the body’s response to repeated exposure. It helps our body learn
to restraint stress. – Mood regulation: the ECS promotes a “good
feeling” by inducing dopamine release in the brain reward pathway. This explains the
euphoria, or the “high”, experienced by marijuana users. THC mode of action is, however,
different from other drugs: it induces dopamine release INDIRECTLY by removing inhibitory
action of GABA on dopaminergic neurons. The ECS is also involved in many other brain
and bodily activities, including memory and learning, appetite and sleeping patterns,
immune functions and fertility. The endocannabinoids are short-acting transmitter
substances. They are synthesized on demand and their signaling is rapidly terminated
by specific enzymes. The amount of endocannabinoid messengers is tightly regulated accordingly
to the body’s needs. This regulation is essential for a modulator that acts to fine-tune
brain activities. Marijuana users consume a much higher amount
of THC. THC is also much more stable than endocannabinoids and can persist in the body
for a much longer period of time. THC overwhelms the endocannabinoid system, overriding normal
brain functions. Because cannabinoid receptors are present in many parts of the brain and
body, the effects of THC are wide-ranging. It can slow down a person’s reaction time,
which could impair driving or athletic skills; disrupt short-term memory and higher thought
processes, which could affect learning capabilities and judgment ability. Higher doses of THC
may also lead to reverse effects. For example, while lower doses of cannabinoids seem to
reduce stress, anxiety, and panic; higher doses may actually promote increased stressful
feelings and fear. Consuming marijuana by smoking may also damage the lungs to a similar
extent as smoking cigarettes. Substantial evidence from animal studies indicates
that marijuana exposure can cause long-term adverse changes in the brain. Rats exposed
to THC before birth, soon after birth, or during early life show significant difficulties
with certain learning and memory tasks later in life. Long-term effects of marijuana in
humans are still debatable mostly due to limitations of conducting research on human beings.
While recreational use of marijuana is WITHOUT doubt harmful, the Cannabis plant may be a
valuable source of medicines. Currently, the two main cannabinoids from the marijuana plant
that are of medical interest are THC and cannabidiol, or CBD. These chemicals are used to increase
appetite and reduce nausea in patients undergoing cancer chemotherapy. They may also be useful
in reducing pain and inflammation, controlling epileptic seizures, and possibly even treating
autoimmune diseases and cancers.