Cannabis is one of the most pharmacologically complex plants on earth. It produces over 500 distinct chemical compounds, more than 100 of which are cannabinoids — a class of molecule found almost nowhere else in nature. Yet most of the conversation around cannabis focuses on a single number: THC percentage. That number tells you very little.
The plant itself
Cannabis sativa is a dioecious flowering plant — it produces separate male and female plants. What's consumed recreationally and medicinally is almost always the unpollinated female flower, commonly called "bud" or "cola". When a female plant is pollinated by a male, it redirects energy into seed production instead of resin, significantly reducing cannabinoid and terpene output.
The resin that coats the female flower is produced in structures called trichomes — tiny hair-like glands visible as a frosted coating on mature buds. Trichomes are where virtually all the cannabinoids and terpenes are concentrated. Under magnification, they look like tiny mushrooms with a bulbous head on a stalk. The density and maturity of trichomes is one of the most reliable visual indicators of potency and harvest readiness.
The endocannabinoid system
To understand why cannabis affects humans the way it does, you need to understand why we have receptors for it in the first place.
The endocannabinoid system (ECS) is a network of receptors and signalling molecules that exists throughout the body and brain. It was only discovered in the early 1990s — ironically, largely because researchers were trying to understand how THC worked. The ECS plays a role in regulating mood, memory, appetite, pain sensation, immune response, and sleep.
The body produces its own cannabinoids (endocannabinoids) — primarily anandamide and 2-AG — which bind to the same receptors that THC, CBD, and other plant cannabinoids target. The two primary receptor types are:
CB1 receptors — concentrated in the brain and central nervous system. This is where THC's psychoactive effects primarily occur. CB1 receptors are densely distributed in regions controlling memory (hippocampus), motor control (basal ganglia), and emotional processing (amygdala).
CB2 receptors — found primarily in immune tissue. Less associated with psychoactivity, more associated with inflammation regulation. CBD has a higher affinity for CB2 relative to THC.
The major cannabinoids
THC (Delta-9-tetrahydrocannabinol)
The primary psychoactive compound. THC is a partial agonist at CB1 receptors — it binds to them but doesn't fully activate them, which is one reason why cannabis overdose, while deeply uncomfortable, is not lethal in the way that opioid overdose is (opioid receptors in the brainstem control breathing; CB1 receptors do not).
In the living plant, THC exists primarily as THCA (tetrahydrocannabinolic acid), which is non-psychoactive. THCA only converts to THC through decarboxylation — the application of heat. This is why raw cannabis doesn't get you high.
CBD (Cannabidiol)
Non-psychoactive, largely because it has very low affinity for CB1 receptors. CBD appears to modulate the ECS indirectly — some research suggests it reduces CB1 receptor sensitivity, which may partly explain why high-CBD strains tend to produce a milder, less anxiety-prone experience than high-THC strains. CBD also interacts with serotonin receptors (5-HT1A), which is the proposed mechanism behind its anxiolytic effects.
CBG (Cannabigerol)
Often called the "mother cannabinoid" because CBGA (its acid form) is the chemical precursor from which the plant synthesises THCA, CBDA, and CBCA. CBG itself is typically present in very low concentrations in mature plants. It has shown antibacterial properties in some studies, and early research suggests it may interact with alpha-2 adrenoceptors involved in mood regulation.
CBN (Cannabinol)
A degradation product of THC — it forms as THC oxidises with age or exposure to light and air. Old, improperly stored cannabis will have elevated CBN. It has mild psychoactive properties at high concentrations. Frequently marketed as a sleep aid, though the evidence base is limited.
CBC (Cannabichromene)
Non-psychoactive. May interact with receptors involved in pain signalling (TRPA1, TRPV1). Some early research suggests it has anti-inflammatory properties distinct from CBD's mechanism.
Terpenes: why two 25% THC strains feel completely different
This is the question that reveals how crude THC percentage is as a quality measure.
Terpenes are aromatic volatile compounds produced in the same trichomes as cannabinoids. They're responsible for the distinctive smell of different cannabis varieties, and there is growing evidence that they directly modify the cannabis experience — not just through smell but through pharmacological interaction with the same receptor systems.
Myrcene — the most common terpene in cannabis. Earthy, musky, slightly fruity. Associated with sedative effects and enhanced membrane permeability (potentially allowing cannabinoids to cross the blood-brain barrier more efficiently). High-myrcene strains are typically associated with heavier body effects.
Limonene — citrus-forward. Uplifting and anxiolytic in some studies. Interacts with serotonin and dopamine pathways.
Pinene — pine scent. May counteract short-term memory impairment associated with THC (acetylcholinesterase inhibition). Bronchodilatory — may increase airway capacity.
Linalool — floral, lavender. Shares a receptor profile with common anti-anxiety compounds (modulates GABA-A receptors). Found in high concentrations in calming varieties.
Caryophyllene — spicy, peppery. Unique among terpenes in that it directly binds to CB2 receptors, making it a functional cannabinoid by activity even though it's structurally a terpene. Anti-inflammatory.
The "entourage effect" — the hypothesis that cannabinoids and terpenes produce stronger and more nuanced effects together than individually — remains scientifically contested but is supported by enough mechanistic data that it's taken seriously in pharmacology research. Ethan Russo's 2011 paper in the British Journal of Pharmacology remains the most cited review of the evidence.
What THC percentage actually tells you
A high THC percentage tells you the maximum theoretical potency of the flower. It says nothing about:
Two strains at 22% THC from different cultivators, grown differently, cured differently, and stored differently can produce dramatically different experiences. A Certificate of Analysis that shows both cannabinoid percentages and a full terpene panel tells you substantially more than a single THC number.
Products listed on Galactica Express Cannabis are required to hold current lab documentation. Ask any listed store for their CoA — if they can't provide one, that's information worth having.