title: Ascending multisynaptic pathways from the trigeminal ganglion to the anterior cingulate cortex.
abstract: By means of retrograde transneuronal transport of rabies virus, ascending multisynaptic pathways from the trigeminal ganglion (TG) to the anterior cingulate cortex (ACC) were identified in the rat. After rabies injection into an electrophysiologically defined trigeminal projection region of the ACC, transsynaptic labeling of second-order neurons via the medial thalamus (including the parafascicular nucleus) was located in the spinal trigeminal nucleus pars caudalis. Third-order neuron labeling occurred in the TG. Most of these TG neurons were medium- or large-sized cells giving rise to myelinated Aδ or Aβ afferent fibers, respectively. By contrast, TG neurons labeled transsynaptically from the orofacial region of the primary somatosensory cortex contained many small cells associated with unmyelinated C afferent fibers. Furthermore, the TG neurons retrogradely labeled with fluorogold injected into the mental nerve were smaller in their sizes compared to those labeled with rabies. Our extracellular unit recordings revealed that a majority of ACC neurons responded to trigeminal nerve stimulation with latencies of shorter than 20ms. Thus, somatosensory information conveyed to the ACC by multisynaptic ascending pathways derived predominantly from myelinated primary afferents (i.e., the medial nociceptive system) and may be used to subserve affective-motivational aspects of pain. Lack of overlap with the lateral nociceptive system is notable and suggests that the medial and lateral nociceptive systems perform separate and non-overlapping functions.
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, 1-8-13 Kandasurugadai, Chiyoda-ku, Tokyo, 101-8310, Japan. iwata-k@dent.nihon-u.ac.jp
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwata
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Miyachi
authors.forename: Michiko
authors.initials: M
authors.lastname: Imanishi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tsuboi
authors.forename: Junichi
authors.initials: J
authors.lastname: Kitagawa
authors.forename: Kohei
authors.initials: K
authors.lastname: Teramoto
authors.forename: Suzuro
authors.initials: S
authors.lastname: Hitomi
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shinoda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kondo
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takada
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D002452:Cell Count / Q000379:methods; D004558:Electric Stimulation / Q000379:methods; D006179:Gyrus Cinguli / Q000166:cytology* / Q000502:physiology*; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011820:Rabies virus / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013266:Stilbamidines / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000166:cytology / Q000502:physiology*
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D013266:Stilbamidines