title: Effects of Neonatal C-Fiber Depletion on Interaction between Neocortical Short-Term and Long-Term Plasticity.
abstract: BACKGROUND
  The primary somatosensory cortex has an important role in nociceptive sensory-discriminative processing. Altered peripheral inputs produced by deafferentation or by long-term changes in levels of afferent stimulation can result in plasticity of cortex. Capsaicin-induced depletion of C-fiber afferents results in plasticity of the somatosensory system. Plasticity includes short-term and long-term changes in synaptic strength. We studied the interaction between paired-pulse facilitation, as one form of short-term plasticity, with long-term potentiation (LTP) in the neocortex of normal and C-fiber depleted freely moving rat.
  
  
  METHODS
  Neonatally capsaicin-treated rats and their controls were allowed to mature until they reached a weight between 250 and 300g. Then animals were anesthetized with ketamine and xylazine. For recording and stimulation, twisted teflon-coated stainless steel wires were implanted into somatosensory cortex or corpus callusom. In experiments for LTP induction, after two weeks of recovery period, 30 high frequency pulse trains were delivered once per day for 12 days. Paired-pulse ratio (PPR) was monitored before and after the induction of LTP in capsaicin-treated and control rats.
  
  
  RESULTS
  Paired-pulse stimulation affected all field potential components at intervals < 200 ms. The largest changes occurred at intervals between 20-30 ms. C-fiber depletion postponed the development of LTP, whereas it had no effect on PPR.
  
  
  CONCLUSIONS
  This finding provides further evidence that the expression of this form of LTP is postsynaptic. Furthermore, these results suggest that the effect of C-fiber depletion on cortical LTP is also postsynaptic and, therefore, is not caused by a decrease in neurotransmitter release.
authors.affiliation: Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Komaki
authors.affiliation: Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Siamak
authors.initials: S
authors.lastname: Shahidi
authors.affiliation: Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Abdolrahman
authors.initials: A
authors.lastname: Sarihi
authors.affiliation: Department of Biology, Bu-Ali Sina University, Hamadan, Iran.
authors.forename: Parisa
authors.initials: P
authors.lastname: Hasanein
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran ; Imam Bagher (as) Institute of Science and Technology, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Lashgari
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Haghparast
authors.affiliation: Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Iraj
authors.initials: I
authors.lastname: Salehi
authors.affiliation: Department of Physiology, Tarbiat Modares University, Tehran, Iran.
authors.forename: Masoomeh Kourosh
authors.initials: MK
authors.lastname: Arami
keywords: C-fiber; Capsaicin; Long-Term Potentiation; Paired-Pulse Facilitation; Paired-Pulse Ratio; Plasticity