The differing types of tyrosine receptors have now been located anatomically, thanks to the sophisticated work going on at Karolinska in Sweden. We have a good relationship with Jorgen Boivie at Karolinska and he has been generous to share information. He is one of the great pain scientists of this generation.
We have emphasized repeatedly that the neurotransmitter, or if you will, the neuromodulator is not as important in understanding function as knowing what the RECEPTOR does. Tyrosine is an amino acid (remember that connected sequences of amino acids constitute a peptide, or if very long, make a protein). with unique characteristics. Although chemically, proteins are one long chain of amino acids, in reality they wind and contort into structures so complex that it is appropriate to call them micromachines.
As they are chemically acted upon or altered, these machines may MOVE, to open or close ion channels, expose receptors which initiate other reactions, etc. These characteristics of composition affect binding angles in how the chinese puzzle of amino acids is fit together into the macromaze of large proteins which contain tyrosine and other amino acids. The amino acid composition imposes bonding angles by virtue of the nuclear/electron forces inherent in molecules (not unlike the attraction or repulsion of magnetic poles) the bonding angles (which can be mathematically calculated from the properties of atoms) ultimately determine the shape or