title: NMDA receptor mediates chronic visceral pain induced by neonatal noxious somatic stimulation.
abstract: NMDA receptors (NMDAR) are important in the development and maintenance of central sensitization. Our objective was to investigate the role of spinal neurons and NMDAR in the maintenance of chronic visceral pain. Neonatal rats were injected with acidic saline adjusted to pH 4.0 in the gastrocnemius muscle every other day for 12 days. In adult rats, NR1 and NR2B subunits were examined in the lumbo-sacral (LS) spinal cord. A baseline, visceromotor response (VMR) to graded colorectal distension (CRD) was recorded before and after administration of the NMDA antagonist, CGS-19755. Extracellular recordings were performed from CRD-sensitive LS spinal neurons and pelvic nerve afferents (PNA) before and after CGS-19755. Rats that received pH 4.0 saline injections demonstrated a significant increase in the expression NR2B subunits and VMR response to CRD>20 mmHg. CGS-19755 (i.v. or i.t.) had no effect in naïve rats, but significantly decreased the response to CRD in pH 4.0 saline injected rats. CGS-19755 had no effect on the spontaneous firing of SL-A, but decreased that of SL-S. Similarly, CGS-19755 attenuates the responses of SL-S neurons to CRD, but had no effect on SL-A neurons or on the response characteristics of PNA fibers. Neonatal noxious somatic stimulation results in chronic visceral hyperalgesia and sensitizes a specific subpopulation of CRD-sensitive spinal neurons. The sensitization of these SL-S spinal neurons is attenuated by the NMDAR antagonist. The results of this study suggest that spinal NMDARs play an important role in the development of hyperalgesia early in life.
authors.affiliation: Division of Gastroenterology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, United States. Electronic address: amiranda@mcw.edu.
authors.forename: Adrian
authors.initials: A
authors.lastname: Miranda
authors.affiliation: Division of Gastroenterology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Aaron
authors.initials: A
authors.lastname: Mickle
authors.affiliation: Division of Gastroenterology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Bruckert
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kannampalli
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Banani
authors.initials: B
authors.lastname: Banerjee
authors.affiliation: Division of Gastroenterology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, United States; Division of Gastroenterology and Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Jyoti N
authors.initials: JN
authors.lastname: Sengupta
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D059350:Chronic Pain / Q000139:chemically induced / Q000378:metabolism*; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D010812:Physical Stimulation / Q000379:methods; D010875:Pipecolic Acids / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D059265:Visceral Pain / Q000139:chemically induced / Q000378:metabolism*
chemical_list: D010875:Pipecolic Acids; D016194:Receptors, N-Methyl-D-Aspartate; C053672:selfotel
keywords: NMDA; Neonatal pain; Visceral hyperalgesia