The effect of neonatal capsaicin treatment on the CGRP-immunoreaction in the trigeminal subnucleus caudalis of mice.
The calcitonin-gene related peptide (CGRP) is a primary afferent neurotransmitter in the trigeminal system. Although a neonatal administration of capsaicin eliminates substance P (SP)-mediated nociceptive responses to induce a permanent functional reduction in C-fibers, little information is available regarding changes in CGRP-immunoreaction in mice undergoing neonatal capsaicin treatment (CP mice). This study examined postnatal changes in the distribution of CGRP-immunoreaction in the trigeminal subnucleus caudalis and trigeminal ganglion of CP mice by immunohistochemical technique and a quantitative analysis. Immunohistochemistry for CGRP in the subnucleus caudalis (Vc) demonstrated two dense distributions of neurons in the CP mice as well as naïve mice: in the marginal layer and the region 400-600 mum deep. The quantitative analysis revealed no significant difference in the density of CGRP immunoreaction between naïve and CP mice 1-8 weeks of age. In the trigeminal ganglion of both groups, the size distribution of CGRPpositive neurons displayed a distribution pattern with one peak in 200-300 mum(2) at week 1 and with two peaks in 200-300 mum(2) and 600-700 mum(2) at week 8 but no significant difference in neural density existed between these regions. When double staining in the naïve mice with CGRP or SP and VR1, a capsaicin receptor, was done, many trigeminal ganglion neurons co-expressed SP- and VR1-immunoreactions, but rarely exhibited CGRP/VR1-co-localization. Taken together with previous data, these current observations suggest that CGRP containing afferent neurons possibly performs differing roles in nociceptive afferent input transmission within the Vc from SP-containing neurons in mice.
Aita
Megumi
M
Division of Oral Anatomy, Niigata University Graduate School of Medical and Dental Sciences, Nigata, Japan.
Maeda
Takeyasu
T
Seo
Kenji
K
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology*; D007150:Immunohistochemistry; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D013373:Substance P / Q000032:analysis / Q000378:metabolism; D050916:TRPV Cation Channels / Q000032:analysis / Q000378:metabolism; D014018:Tissue Distribution; D014275:Trigeminal Caudal Nucleus / Q000187:drug effects* / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism
D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin