title: Postnatal development of excitation propagation in the trigeminal subnucleus caudalis evoked by afferent stimulation in mice.
abstract: The postnatal development of nociceptive afferent activity expansion and its modulation features were examined in mice using an optical imaging technique. Developing mice (1-2 weeks old (N1-2 w), 3-4 weeks old (N3-4 w), 5-6 weeks old (N5-6 w) and 7-8 weeks old (N7-8 w)) and neonatally capsaicin-treated mice were used. The propagation of neuronal excitation was measured by changes in fluorescent intensity in horizontal brain stem slices evoked by electrical stimulation to the trigeminal spinal tract. A single-pulse stimulation evoked excitation propagation in the trigeminal caudalis (Vc). The propagation area was larger in N1-2 w than in N7-8 w, and no differences were observed between capsaicin-treated and naive mice in the same age groups. Repetitive stimulation (100 Hz, 30 pulses) elicited long-lasting and widespread excitation propagation. The excitation propagation area was significantly larger in N7-8 w than in N1-2 w, N3-4 w and N5-6 w. This propagation was suppressed by 5 microM L-703.606, an NK1-receptor antagonist, suggesting that the repetitive stimulation-elicited excitation may require substance-P releases. Morphological observations demonstrated that the neural network in the Vc had grown by postnatal week 5. These results suggest that nociceptive afferent activity co-operatively matures with development of the network structure in the Vc, and that a mechanism for prolonged increase in central excitability is established during a later postnatal period.
authors.affiliation: Division of Dental Anesthesiology, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, 5274, 2 Ban-cho, Gakkocho-dori, Niigata 951-8514, Japan. seo@dent.niigata-u.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Seo
authors.forename: Naoshi
authors.initials: N
authors.lastname: Fujiwara
authors.forename: Kiichi
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Maeda
authors.forename: Genji
authors.initials: G
authors.lastname: Someya
mesh_terms: D000344:Afferent Pathways / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000379:methods; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004347:Drug Interactions; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D064729:Neurokinin-1 Receptor Antagonists; D011812:Quinuclidines / Q000494:pharmacology; D016622:Silver Staining / Q000379:methods; D013997:Time Factors; D014275:Trigeminal Caudal Nucleus / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D064729:Neurokinin-1 Receptor Antagonists; D011812:Quinuclidines; C076851:L 703606; D016291:Dizocilpine Maleate; D002211:Capsaicin