Postnatal development of excitation propagation in the trigeminal subnucleus caudalis evoked by afferent stimulation in mice.
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.
Seo
Kenji
K
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
Fujiwara
Naoshi
N
Takeuchi
Kiichi
K
Maeda
Takeyasu
T
Someya
Genji
G
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*
D018691:Excitatory Amino Acid Antagonists; D064729:Neurokinin-1 Receptor Antagonists; D011812:Quinuclidines; C076851:L 703606; D016291:Dizocilpine Maleate; D002211:Capsaicin