... small,thinly myelinated A- delta afferent neurons releasesubstance P into lamina I and lamina V in the dorsal horn of the spinal cord. Activated C fibres similarly releasesubstance P into lamina II. ... 14:74-85.3. Aaron LA, Bradley LA, Alarcon GS, Triana-Alexander M, AlexanderRW, Martin MY, Alberts KR: Perceived physical and emotionaltrauma as precipitating events in fibromyalgia. Associationswith ... predispose to pain, what are the pathways involved? Changes in oestrogen levels in the plasma are accompanied by changes in a variety of neurotransmitters, particularly serotonin and substance P[71,72]....