title: Parallel "pain" pathways arise from subpopulations of primary afferent nociceptor.
abstract: A major unanswered question concerning "pain" circuitry is the extent to which different populations of primary afferent nociceptor engage the same or different ascending pathways. In the present study, we followed the transneuronal transport of a genetically expressed lectin tracer, wheat germ agglutinin, in Na(V)1.8-expressing nociceptors of the nonpeptide class. We found that interneurons of lamina II are at the origin of the major ascending circuits targeted by the nonpeptide nociceptors. These interneurons contact lamina V projection neurons, which in turn predominantly target fourth-order neurons in the amygdala, hypothalamus, bed nucleus of the stria terminalis, and to a remarkable extent, the globus pallidus. These circuits differ greatly from the lamina I-based projection that is targeted by the peptide class of nociceptors. Our results indicate that parallel, perhaps independent pain pathways arise from different nociceptor classes and that motor as well as limbic targets predominate in the circuits that originate from the nonpeptide population.
authors.affiliation: Department of Anatomy and W.M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, California 94143, USA. bjoao@phy.ucsf.edu
authors.forename: Joao M
authors.initials: JM
authors.lastname: Braz
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Nassar
authors.forename: John N
authors.initials: JN
authors.lastname: Wood
authors.forename: Allan I
authors.initials: AI
authors.lastname: Basbaum
mesh_terms: D000344:Afferent Pathways / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000503:physiopathology; D002452:Cell Count / Q000379:methods; D005455:Fluorescent Antibody Technique / Q000379:methods; D007395:Interneurons / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D062559:NAV1.8 Voltage-Gated Sodium Channel; D009415:Nerve Net / Q000378:metabolism* / Q000503:physiopathology; D016571:Neural Networks, Computer; D009475:Neurons, Afferent / Q000378:metabolism*; D009619:Nociceptors / Q000378:metabolism* / Q000502:physiology; D010146:Pain / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics; D013116:Spinal Cord / Q000166:cytology*; D014909:Wheat Germ Agglutinins / Q000235:genetics / Q000378:metabolism
chemical_list: D062559:NAV1.8 Voltage-Gated Sodium Channel; D010320:Parvalbumins; C568318:Scn10a protein, mouse; D015222:Sodium Channels; D014909:Wheat Germ Agglutinins