In her research, Dr Pert uncovered the chemical processes that trigger our moods, behaviours and beliefs. She explains how receptors function as sensing molecules- scanners. Just as our eyes and ears, nose, tongue, fingers, and skin act as sense organs so, too, do the receptors only at a cellular level. Different cocktails of neurochemicals cause different emotional experiences and changes in behaviour.
(a) Receptors
"The first component of the molecules of emotion is a molecule that is found on the surface of cells in the body and brain called the opiate receptor….
Measurement! It is the very foundation of the modern scientific method, the means by which the material world is admitted into existence. Unless we can measure something, science won’t concede it exists which is why science refuses to deal with such “non things” as emotions, soul, spirit, the mind…
The receptors are molecules and are made up of proteins, tiny amino acids strung together in crumpled chains looking something like beaded necklaces that have folded in on themselves. If you were to assign a different colour to each of the receptors that scientists have identified, the average cell would appear as a multi-coloured mosaic of at least 70 different hues- 50,000 of one type of receptor, 10,000 of another, 100,000 of a third and so on. A typical neuron (nerve cell) may have millions of receptors on its surface…
Basically, receptors function as sensing molecules- scanners. Just as our eyes and ears, nose, tongue, fingers, and skin act as sense organs so, too, do the receptors only at a cellular level. They hover in the membranes of your cells, dancing and vibrating, waiting to pick up messages carried by other vibrating little creatures, also made up of amino acids, which come cruising along-diffusing is the technical word- through the fluids surrounding each cell. We like to describe these receptors as “keyholes”, although that is not an altogether precise term for something that is constantly moving, dancing in a rhythmic, vibratory way. (p.21-23)
(b) Ligands
If receptors are the first components of the molecules of emotion, then ligands are the second. The word ligand comes from the Latin ligare, that which binds, sharing its origin with the word religion.
Ligand is the term for any natural or man made substance [pharmaceutical] that binds selectively on its own specific receptor on the surface of a cell. The ligand bumps onto the receptor and slips off, bumps back on, slips back off again. The ligand bumping on is what we call the binding, and in the process, the ligand transfers its message via its molecular properties to the receptor…
The receptor having received a message, transmits it from the surface of the cell deep into the cell’s interior, where the message can change the state of the cell dramatically …In short the life of the cell, what it is up to at any moment, is determined by which receptors are on its surface, and whether those receptors are occupied by ligands or not. On a more global scale, these minute physiological phenomena at the cellular level can translate to large changes in behaviour, physical activity, even mood…
(P 25) Ligands are generally much smaller molecules than the receptors they bind to, and they are divided into three chemical types.
The first type of ligand comprises the classical ‘neurotransmitters’ which are small molecules with such unwieldy names as acetylcholine, norepinephrine (noradrenaline), dopamine, histamine, glycine, GABA, and serotonin.
These are the smallest, simplest of molecules, generally made in the brain to carry information across the gap or synapse, between one neuron and the next. Many start out as simple amino acids, the building blocks of protein, and then get a few atoms added here and there. …
A second category of ligands is made up of ‘steroids’, which include the sex hormones testosterone, progesterone, and estrogen. All steroids start out as cholesterol, which gets transformed by a series of biochemical steps into a specific kind of hormone…hormones, such as cortisol, … are secreted by the outer layer of the adrenal glands under stress.
…the largest category, constituting perhaps 95% of them all, are the peptides. As we shall see these chemicals play a wide role in regulating practically all life processes, and are indeed the other half of the equation of what I call the molecules of emotion. Like receptors, peptides are made up of strings of amino acids…visualize the following: If the cell is the engine that drives all life, then the receptors are the buttons on the control panel of that engine, and a specific peptide (or other kind of ligand) is the finger that pushes the button and gets things started."
The Chemical Brain
…But the yet-to-be-named neuroscience was so focused, for so long, on the concept of the nervous system as an electrical network based on neuron-dendrite-neurotransmitter connections, that even when we had the evidence, it was hard to grasp the idea that the ligand-receptor system represented a second nervous system, one that operated on a much longer time scale, over much greater distances. Especially difficult to accept was that this chemical-based system was one indisputably more ancient and far more basic to the organism. There were peptides such as endorphins, for instance, being made inside the cells long before there were dendrites, axons, or even neurons-in fact, before there were brains.
…The peptides, on the other hand, while they sometimes act like neurotransmitters, swimming across the synaptic cleft, are much more likely to move through extracellular space, swept along in the blood and cerebrospinal fluid, travelling long distances and causing complex and fundamental changes in the cells whose receptors they lock onto.
…In the wake of discoveries in the 1980’s, these receptors and ligands have come to be seen as “information molecules”- the basic units of a language used by cells throughout the organism to communicate across systems such as the endocrine, neurological, gastrointestinal and even the immune system. Overall the musical hum of the receptors as they bind to their many ligands, often in far flung parts of the organism, creates an integration of structure and function that allows the organism to run smoothly, intelligently.” (P.26)
Here is an animated version of this receptor-ligand activity.
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