Answer:
myofascial trigger points are local super contracted muscle fibers. Due this contraction (contracture) the capillaries are obstructed, which leads to ischemia en hypo perfusion of the muscle tissue. This leads to a increase of the pH, which starts to sensitize muscle nociceptors. Beside this a couple of other chemicals are released, among them Substance P, Bradykinin and several cytokines.
The micro dialysis studies of dr. Jay Shah showed significant increases of the concentration of these chemicals in active myofascial trigger points. Calcitonin gene related peptide (CGRP) is one of these chemicals. This increases the release of Acetyl choline, decreases the synthesis of cholinesterase and upregulates the ACh receptors in the synaptic cleft. Therefore the release of chemicals produces pain and augments the contracture of the muscle fibers. A chronic situation is born.