title: Spinal substance P release in vivo during the induction of long-term potentiation in dorsal horn neurons.
abstract: Long-term potentiation (LTP) in wide dynamic range (WDR) neurons in the dorsal horn has been suggested to contribute to central sensitization and the development of chronic pain. Indirect experimental evidence indicates an involvement of substance P (SP), in this respect. The aim of the present study was to monitor the extracellular level of substance P-like immunoreactivity (SP-LI) in the dorsal horn of the rat during and after induction of LTP in WDR neurons in vivo. Electrophysiological recordings of single (WDR) neurons were performed in parallel with microdialysis in the dorsal horn under urethane-anaesthesia. The amount of SP-LI in the microdialysate was determined by radioimmunoassay. As previously shown, high frequency conditioning stimulation of the sciatic nerve induced an increased firing response of WDR neurons. An increased response to C-fibre stimulation, but not A-fibre stimulation, could be determined. A significant increase of the extracellular level of SP-LI in the dorsal horn was detected during, but not after, induction of LTP. These data suggest that SP may be involved in the induction of LTP by high frequency stimulation. However, the maintenance of spinal LTP following high frequency peripheral nerve stimulation does not seem to depend on an increased release of SP.
authors.affiliation: Department of Physiology and Pharmacology, Division of Pharmacological Pain Research, Karolinska Hospital, Karolinska Institutet, Stockholm, Sweden. abdullah.afrah@fyfa.ki.se
authors.forename: Abdullahi Warsame
authors.initials: AW
authors.lastname: Afrah
authors.forename: Atle
authors.initials: A
authors.lastname: Fiskå
authors.forename: Johannes
authors.initials: J
authors.lastname: Gjerstad
authors.forename: Henrik
authors.initials: H
authors.lastname: Gustafsson
authors.forename: Arne
authors.initials: A
authors.lastname: Tjølsen
authors.forename: Leif
authors.initials: L
authors.lastname: Olgart
authors.forename: Carl Olav
authors.initials: CO
authors.lastname: Stiller
authors.forename: Kjell
authors.initials: K
authors.lastname: Hole
authors.forename: Ernst
authors.initials: E
authors.lastname: Brodin
mesh_terms: D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology; D004558:Electric Stimulation; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D017774:Long-Term Potentiation / Q000502:physiology*; D017551:Microdialysis; D009412:Nerve Fibers / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D020671:Posterior Horn Cells / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000166:cytology / Q000502:physiology; D013373:Substance P / Q000378:metabolism*
chemical_list: D013373:Substance P