Vanilloid receptor 1-like receptor-immunoreactive primary sensory neurons in the rat trigeminal nervous system.
Immunohistochemistry for vanilloid receptor 1-like receptor (VRL-1), a candidate transducer for high-threshold noxious heat, was performed on rat trigeminal primary sensory neurons. The immunoreactivity was detected in 14% of the trigeminal ganglion cell bodies, while the neurons in the mesencephalic trigeminal tract nucleus were almost devoid of it (0.5%). The immunoreactive neurons in the trigeminal ganglion were mostly of medium to large size (mean+/-S.D. of 956+/-376microm(2)). Nerve bundles in the tooth pulp, periodontal ligament, facial skin and oral mucosa contained VRL-1-positive smooth nerve fibers. The immunoreactivity could not be traced to the isolated nerve fibers, except in the tooth pulp. In the brainstem trigeminal nuclear complex, a notable concentration of the immunoreactivity was seen in laminae I and II of the medullary dorsal horn. Thirty-seven per cent of the trigeminal ganglion neurons retrogradely labeled from the tooth pulp exhibited VRL-1 immunoreactivity, while the immunoreactivity was detected in only 9% of those labeled from the skin. Co-expression of calcitonin gene-related peptide was common among the VRL-1-immunoreactive tooth pulp neurons (45%) and cutaneous neurons (25%). Moreover, as many as 41% of the VRL-1-immunoreactive tooth pulp neurons co-expressed parvalbumin immunoreactivity. Parvalbumin immunoreactivity was never detected in the VRL-1-immunoreactive cutaneous neurons. From the findings of the present study, we propose that large primary neurons responding to high-threshold noxious heat are abundant in the tooth pulp, but not in the facial skin.
Ichikawa
H
H
Second Department of Oral Anatomy and Biodental Research Center, Okayama University Dental School, 2-5-1 Shikata-cho, 700-8525, Okayama, Japan. hiroichi@dent.okayama-u.ac.jp
Sugimoto
T
T
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D048429:Cell Size / Q000502:physiology; D003782:Dental Pulp / Q000294:innervation / Q000502:physiology; D005145:Face / Q000294:innervation / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009619:Nociceptors / Q000166:cytology / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011955:Receptors, Drug / Q000378:metabolism*; D012867:Skin / Q000294:innervation / Q000378:metabolism; D050916:TRPV Cation Channels; D013823:Thermoreceptors / Q000166:cytology / Q000378:metabolism; D013697:Thermosensing / Q000502:physiology; D012668:Trigeminal Ganglion / Q000166:cytology / Q000378:metabolism*; D014279:Trigeminal Nucleus, Spinal / Q000166:cytology / Q000378:metabolism*
D010320:Parvalbumins; D011955:Receptors, Drug; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D015740:Calcitonin Gene-Related Peptide