Cotton-mouth Every cannabis user throughout the world is sure to be familiar with that sticky, dry, pasty sensation that affects the mouth after smoking cannabis. In fact, it is so inevitable that people rarely question the mechanism at work behind this strange little phenomenon—except for a handful of researchers who believe they know why.
Every cannabis user throughout the world is sure to be familiar with that sticky, dry, pasty sensation that affects the mouth after smoking cannabis. In fact, it is so inevitable that people rarely question the mechanism at work behind this strange little phenomenon—except for a handful of researchers who believe they know why.
How is saliva formed?
Firstly, we shall take a brief look at the process of saliva production. It appears that saliva formation involves a two-stage process: initially, specialised cells known as acinar cells secrete a fluid that is similar in composition to plasma; this fluid then passes through the salivary ducts on its way to the oral cavity, and as it does so, sodium and chloride is removed from it and potassium and bicarbonate is added, to produce the final ‘hypotonic solution’ that is secreted into the mouth.
Secretion of saliva is controlled by the parasympathetic nervous system, which causes the activation of receptors in the salivary glands via impulses from the chorda tympani nerve. This important nerve originates in the taste buds before travelling through the submandibular ganglion (the cluster of nerve cells in the submandibular gland) and on to the brain. The chorda tympani nerve releases a compound known as acetylcholine, which is one of the body’s main saliva-stimulating substances and works directly on the receptors of the submandibular gland.
Another important compound involved in salivary secretions is known as norepinephrine. This compound is released by the preganglionic nerves that lie upstream from the submandibular ganglion. It works directly on the myoepithelial cells that surround the acinar cells by causing them to contract, which then leads to the secretion of saliva.
CB-receptors in the salivary glands
It has been noted in various studies that cannabis use causes oral dryness. In 1986, a study into the effects of cannabidiol (CBD) noted that the side-effects of administration of oral CBD included dry mouth; since then, several other studies have also observed cannabinoid-induced oral dryness. Oral dryness is known as xerostomia among scientists.
Perhaps the most in-depth study on cannabis-induced xerostomia to date was performed by researchers at the University of Buenos Aires, Argentina in 2006. The researchers found that cannabinoid receptors type 1 and 2 are present in the submandibular glands, which lie beneath the floor of the mouth and are responsible for producing 60-67% of the saliva.
The researchers found that the endocannabinoid agonist anandamide (AEA) binds with high affinity to the glandular cannabinoid receptors and blocks the action of the saliva-inducing compounds norepinephrine and methacholine, leading to a decrease in the secretion of saliva. As mentioned above, these saliva-inducing compounds are part of the normal working of the parasympathetic nervous system that is responsible for various metabolic processes related to food intake, appetite and anticipation of eating. THC is also an agonist of the CB receptors, and is likely to affect the receptors of the submandibular glands in a similar manner.
The fundamental role of the endocannabinoid system
Interestingly, the Buenos Aires study also concluded that that the role of the endocannabinoid system is not limited to blocking signals at the submandibular glands themselves. The nervous impulses that are expressed via the chorda tympani originate in the brain, and the researchers postulated that the intravenous administration of cannabinoids via the femoral vein exerted their primary effect via the submandibular glands but may also have acted on the cannabinoid receptors in the brain itself, and that a central nervous system mechanism helps to control production of saliva at glandular level.
The fact that the endocannabinoid system is so fundamentally involved with the inhibition of salivary secretions implies that it also has a role to play in causing the production of saliva. If an agonist or antagonist of the cannabinoid receptors inhibits salivation, it is likely that an inverse agonist such as the synthetic cannabinoid AM-251 may cause a reversal of this effect and an increase in salivation. Indeed, the 2006 study also demonstrated that presence of AM-251 partly reversed the effect of AEA (although there appears to be a lack of consensus as to whether AM-251 is an antagonist or an inverse agonist).
What to do if you experience dry mouth
Experiencing a dry mouth and throat after cannabis use is extremely common, and often it does not take much cannabis to induce this effect. However, during a heavy session, the dry-mouth effect can often increase until it becomes extremely unpleasant, to the point that even drinking water or other beverages makes little difference.
If experiencing unpleasant cotton-mouth, remaining hydrated will mitigate the issue to some extent. Chewing gum can also help, as the action of chewing stimulates the salivary glands to produce more saliva. Similarly, foodstuffs that require decisive chewing such as dried fruit or beef jerky can also help to stimulate production of saliva. For more complete relief, using a demulcent (a substance that coats a mucous membrane with a moist ‘film’) designed for oral use should suffice. Many different prescription medications can cause users to experience dry mouth, so there are numerous oral demulcents that are commercially available to combat the problem.
In the future, research into the specific nature of the endocannabinoid system and how it controls the process of salivation may yield targeted products that can reverse the effect of xerostomia—not just for those who have smoked a little too much cannabis, but also for individuals suffering from a range of conditions (or taking certain medications) that cause a permanent state of cotton-mouth.