Some science behind the scenes
Receptors and ligands
Each kind of ligand can bind to only certain receptor shapes. Each cell typically has many receptors, of many different kinds. Simply put, a receptor functions as a keyhole that sets off a lot of functional activity once you insert the correct ligand ‘key’.
Although if you ask a biochemist, he will then go on to talk about neural pathways and biological actions, I think it is more helpful to switch over to the functional effects.
Once into the microprocessor that is the cell, the software starts to take over and you get functions activating. And these functions we all recognise. In the mind for example we might get pain, sadness, happiness, euphoria, sedation, lethargy, weariness, joy, delight. In the body we might get more concrete activity such as digestion, burping, beating heart, ‘wee-ing’ and ‘poo-ing’, laughing, crying, breathing and so on. Every cell is like a little hardware microprocessor with its own software functions.
The cell knows which functions it needs to activate because it knows which overall cell aggregation it belongs to – see Aggregation.
Thus to understand how drugs work you need to imagine that a signal comes in from the drug you have taken in the form of a ligand. The ligand is simply a chemical base for a spirit based message. It binds itself to one of the appropriate receptors in your cells somewhere in your body after having travelled around the body in your blood stream. And by attaching itself to a receptor it delivers the message to the functions of the cell and triggers a function that you already possess, but which may not normally be activated. So for example in comes the little ligand from the opium you have just eaten, it binds to the opioid receptor in your cell and the function of euphoria might be activated.
What this means is that you are biologically constructed to accept very many of these ligands and these substances. You have, for example, an opioid receptor and a receptor for various sorts of hallucinogenic mushrooms!