Receptors are considered the first component of the molecules of emotion by Pert, and ligands are considered the second (Pert, 1997, 24). A receptor is a specialized area on a cell surface that a ligand binds to. A ligand is a natural or manmade substance which binds to its own specific receptor on the surface of a cell. The two fit together like a lock (receptor) and key (ligand). The ligands bind briefly to their receptors, initiating a change in the receptor which sets various events in motion within the cell, e.g. making a new protein, starting cell division, or opening ion channels. Ligands can be small molecules such as neurotransmitters like acetylcholine, dopamine, and epinephrine; steroids, such as cortisol, and testosterone; and peptides, strings of amino acids.
When Pert refers to emotions, she includes not only such human experiences as anger, fear, joy, and sadness, but also drive states such as hunger and thirst, and other subjective experiences such as spiritual inspiration, awe, and bliss (Pert, 1997, 132). For a long time, it has been held by neuroscientists that emotions are controlled by certain areas of the brain (133). Mapping of emotions to specific brain areas was carried out in the 1920s by Wilder Penfield at McGill University in Montreal. However, more recent research has shown the presence of almost every neuropeptide receptor in areas such as the dorsal horn of the spinal cord, which is the first synapse within the nervous system where all somatosensory information is processed (141). There is no longer any doubt that the emotional brain is not confined just to the amygdala, hippocampus, and hypothalamus. In almost all locations where information from any of the five senses enters the nervous system, high concentrations of neuropeptide receptors exist.
Emotional and bodily sensations are intimately connected in a bidirectional network in which each can alter the other (Pert, 1997, 142). ...