title: Interactions between superficial and deep dorsal horn spinal cord neurons in the processing of nociceptive information.
abstract: In acute rat spinal cord slices, the application of capsaicin (5 μm, 90 s), an agonist of transient receptor potential vanilloid 1 receptors expressed by a subset of nociceptors that project to laminae I-II of the spinal cord dorsal horn, induced an increase in the frequency of spontaneous excitatory and spontaneous inhibitory postsynaptic currents in about half of the neurons in laminae II, III-IV and V. In the presence of tetrodotoxin, which blocks action potential generation and polysynaptic transmission, capsaicin increased the frequency of miniature excitatory postsynaptic currents in only 30% of lamina II neurons and had no effect on the frequency of miniature excitatory postsynaptic currents in laminae III-V or on the frequency of miniature inhibitory postsynaptic currents in laminae II-V. When the communication between lamina V and more superficial laminae was interrupted by performing a mechanical section between laminae IV and V, capsaicin induced an increase in spontaneous excitatory postsynaptic current frequency in laminae II-IV and an increase in spontaneous inhibitory postsynaptic current frequency in lamina II that were similar to those observed in intact slices. However, in laminae III-IV of transected slices, the increase in spontaneous inhibitory postsynaptic current frequency was virtually abolished. Our results indicate that nociceptive information conveyed by transient receptor potential vanilloid 1-expressing nociceptors is transmitted from lamina II to deeper laminae essentially by an excitatory pathway and that deep laminae exert a 'feedback' control over neurons in laminae III-IV by increasing inhibitory synaptic transmission in these laminae. Moreover, we provide evidence that laminae III-IV might play an important role in the processing of nociceptive information in the dorsal horn.
authors.affiliation: Département Nociception et Douleur, Institut des Neurosciences Cellulaires et Intégratives, UPR 3212 Centre National de la Recherche Scientifique, Université de Strasbourg, 21 rue René Descartes, F-67084 Strasbourg, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Petitjean
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Rodeau
authors.forename: Rémy
authors.initials: R
authors.lastname: Schlichter
mesh_terms: D000200:Action Potentials; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D025461:Feedback, Physiological; D053444:Inhibitory Postsynaptic Potentials; D008297:Male; D055369:Miniature Postsynaptic Potentials; D059225:Nociception / Q000187:drug effects / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology*; D020671:Posterior Horn Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018689:Sensory System Agents / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D018689:Sensory System Agents; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D013779:Tetrodotoxin; D002211:Capsaicin