Visceral pain: the neurophysiological mechanism. Handb Exp Pharmacol 2009(194):31-74
Date
08/06/2009Pubmed ID
19655104Pubmed Central ID
PMC3156094DOI
10.1007/978-3-540-79090-7_2Scopus ID
2-s2.0-70349907774 (requires institutional sign-in at Scopus site) 179 CitationsAbstract
The mechanism of visceral pain is still less understood compared with that of somatic pain. This is primarily due to the diverse nature of visceral pain compounded by multiple factors such as sexual dimorphism, psychological stress, genetic trait, and the nature of predisposed disease. Due to multiple contributing factors there is an enormous challenge to develop animal models that ideally mimic the exact disease condition. In spite of that, it is well recognized that visceral hypersensitivity can occur due to (1) sensitization of primary sensory afferents innervating the viscera, (2) hyperexcitability of spinal ascending neurons (central sensitization) receiving synaptic input from the viscera, and (3) dysregulation of descending pathways that modulate spinal nociceptive transmission. Depending on the type of stimulus condition, different neural pathways are involved in chronic pain. In early-life psychological stress such as maternal separation, chronic pain occurs later in life due to dysregulation of the hypothalamic-pituitary-adrenal axis and significant increase in corticotrophin releasing factor (CRF) secretion. In contrast, in early-life inflammatory conditions such as colitis and cystitis, there is dysregulation of the descending opioidergic system that results excessive pain perception (i.e., visceral hyperalgesia). Functional bowel disorders and chronic pelvic pain represent unexplained pain that is not associated with identifiable organic diseases. Often pain overlaps between two organs and approximately 35% of patients with chronic pelvic pain showed significant improvement when treated for functional bowel disorders. Animal studies have documented that two main components such as (1) dichotomy of primary afferent fibers innervating two pelvic organs and (2) common convergence of two afferent fibers onto a spinal dorsal horn are contributing factors for organ-to-organ pain overlap. With reports emerging about the varieties of peptide molecules involved in the pathological conditions of visceral pain, it is expected that better therapy will be achieved relatively soon to manage chronic visceral pain.
Author List
Sengupta JNMESH terms used to index this publication - Major topics in bold
Action PotentialsAfferent Pathways
Analgesics
Animals
Behavior, Animal
Disease Models, Animal
Humans
Hyperalgesia
Mechanotransduction, Cellular
Pain
Pain Measurement
Pain Threshold
Receptors, Neurotransmitter
Sensory Receptor Cells
Viscera
