Cannabinoids occur naturally inside (endogenous) and outside (exogenous)
are bodies. These substances act on receptors in various pathways involved in
normal metabolism and make up what is known is the endocannabinoid system.
This system is present in all mammals. The body’s natural cannabinoid messengers
are anandamide and 2-AG. CB1 receptors are those receptors located in the central
nervous system while CB2 receptors are mainly present in the periphery.
Endocannabinoids act on these receptors across the junction of nerve cells basically
resulting in either release or inhibition of different neurotransmitters.
The cannabinoids derived from cannabis known as phytocannabinoids. THC,
CBD, and CBN are the most well known phytocannabinoids. THC is the most
psychoactive of the three, whereas the others have garnered interest due to a variety
of potentially healing properties. These substances bind to various endocannbinoid
receptors throughout the body, though some preferentially bind to certain kinds.
This is true of CBD, which seems to have more of an affinity for CB2 receptors, and
this is likely one of the reasons it has less of a psychoactive effect compared to THC.
Cannabinoids have been used medicinally for thousands of years, though it is only
recently that Western culture has acknowledged application of these substances in
modern medicine.
It is true that there is considerable data lacking in terms of using
cannabinoids in human and veterinary medicine. Much of the current scientific data
available is derived from work in lab animals, especially rodents. Research involving
the endocannabinoid system and use of cannabinoids for therapeutic purposes has
highlighted that fact that the mechanism of action of cannabinoids is very complex.
They can cause inhibition of acetylcholine, dopamine, GABA, histamine, serotonin
and inflammatory cytokine release. These are all naturally occurring substances
involved in the sensing of pain, development of mood, regulation of appetite,
stimulation of nausea, and cell growth and replication. They can also bind to
seratonin receptors which impacts the development of anxiety. Because of the
complexity of their interactions, it is clear cannabinoids can and do produce a large
number of physiological effects, many potentially beneficial.
It is important to underscore that while some scientific information is
available on the use of cannabinoids and their action on the endocannabinoid
receptors found in humans and animals alike, little research has been done in
companion animal species. Dogs are reported to have more endocannabinoid
receptors in their brains compared to humans or even other animals. That may be
one reason why we see more marijuana toxicity in dogs versus people or cats. The
implication here is this may not be the only way that endocannabinoid systems
differ from one species to the next, and so therefore data extrapolated from research
done on lab animals or even in humans, while very promising, is not substitute for
desperately needed studies done with dogs, cats, and even horses. Due to
heightening public interest, media attention, and legalization effort, newer scientific
information can be fully expected in the years to come, though it surprisingly lags
behind research involving other areas of drug research.