What a veterinary surgeon knows about the biology of CBD.
When I explain CBD to clients, I usually start with the same sentence: every mammal you have ever known — yourself, your dog, your cat, the horse in the field next door — possesses the same fundamental biological network that makes CBD work. It's called the endocannabinoid system. It's ancient. It's universal. And it's the reason a compound extracted from a plant can have biological effects in such diverse animals.
This article is about that system. It's more technical than some of what we write, but understanding it properly is the difference between thinking of CBD as a mysterious wellness trend and understanding it as a well-characterised biological mechanism.
The endocannabinoid system (ECS) is a regulatory network of receptors, signalling molecules, and enzymes found throughout the body. It was discovered in the 1990s, largely as a consequence of researchers trying to understand how THC — the psychoactive compound in cannabis — exerted its effects. The system was named after cannabis because that's how we found it, not because it has anything inherently to do with the plant.
The ECS has three main components:
Receptors: CB1 (primarily in the central nervous system, gut, and some immune cells) and CB2 (primarily in immune cells, peripheral nervous system, and various tissues).
Endocannabinoids: Signalling molecules produced by the body itself. The two main ones are anandamide (from the Sanskrit "ananda," meaning bliss) and 2-arachidonoylglycerol (2-AG).
Enzymes: FAAH (fatty acid amide hydrolase) and MAGL (monoacylglycerol lipase) break down endocannabinoids after they've done their job.
The ECS doesn't have a single function. It modulates pain signalling, inflammatory responses, mood, appetite, sleep, memory, immune function, and cellular stress responses. It acts as a rheostat — a fine-tuning system that keeps other biological systems in balance.
Here's where a veterinary perspective is useful. The ECS is conserved across all mammals — but not identical. There are meaningful species differences that pet owners and even some human wellness writers tend to miss.
Here's a point that even some wellness brands get wrong: CBD does not bind strongly to CB1 or CB2 receptors. That's not how it works.
Instead, CBD is what pharmacologists call an "allosteric modulator" — it changes the shape of the receptor in a way that affects how other molecules (including the body's own endocannabinoids) bind to it. It also inhibits FAAH, which means the body's own anandamide persists longer before being broken down. And it interacts with several non-cannabinoid receptors — including the serotonin 5-HT1A receptor, TRPV1 (involved in pain and inflammation), and PPAR-gamma (involved in inflammation and metabolism).
This multi-target action is part of why CBD is hard to study with traditional pharmacological methods. Most drugs have a single, clearly-defined mechanism. CBD has several, which is also why the "entourage effect" — the synergistic action of CBD with other plant compounds — is thought to be significant.
I want to be careful here, because this is where a lot of CBD writing gets sloppy. The evidence base varies enormously depending on what condition you're asking about.
Understanding the ECS shapes how we think about CBD formulation. A few specific decisions that follow from the science:
The endocannabinoid system is real, it's biologically fundamental, and it's the reason CBD has effects at all. It's also the reason those effects vary across species and individuals. Understanding it properly is what separates a well-designed CBD product from a fashionable one.
If you have specific questions about CBD in a species I haven't covered, or about a particular clinical scenario, email me. It's genuinely the kind of thing I find interesting to discuss.
Alastair Greenway MRCVS
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