neurochemical mediators of pain

Etiology: 1) sensory neurons - glutamate - ATP - bradykinin - 5-hydroxytryptamine (5-HT) - histamine - arachidonic acid metabolites - nitric oxide - calcitonin gene-related peptide (CGRP) - mechanotransduction (mechanisms poorly understood) 2) ascending pathway (dorsal horn neurons) - glutamate - substance P - neurotensin - cholecystokinin - somatostatin 2) descending pathway (midbrain & spinal cord) - serotonin - norepinephrine - gamma-aminobutyric acid (GABA) - glycine - acetylcholine 3) assorted areas (brain, spinal cord, nerves, ganglia) - dopamine - adenosine - neuropeptide Y - opioid receptors - mu receptor type most often associated with pain - endogenous opioids - endorphins - enkephalins - dynorphins