Innervation of the equine mature and immature proximal sesamoid bone by calcitonin gene-related peptide and substance P-containing nerves.
OBJECTIVE
To localize and determine relative frequency of occurrence of calcitonin gene-related peptide (CGRP) and substance P (SP) fibers in the proximal sesamoid bones (PSB) and adjacent structures in sound horses.


METHODS
4 foals and 3 adult horses.


METHODS
Medial PSB and adjacent ligaments of both forelimbs were collected, flushed, and fixed in buffered 4% formalin. The left PSB were cut into 5 longitudinal, sagittally oriented slabs, and the right PSB were cut into 5 transverse slabs. After decalcification in EDTA, slices were transferred to a 30% sucrose solution, deep frozen, sectioned (80 microm), and stored in Tris-buffered saline solution for free-floating immunocytochemical processing, staining of which was performed by use of the peroxidase-antiperoxidase method with polyclonal rabbit antibodies against CGRP and SP. Sections were examined by light microscopy.


RESULTS
Calcitonin gene-related peptide and SP fibers were present throughout the PSB; in ligaments, they were concentrated at the attachment sites. Presentation of the fibers, the innervation pattern, and intensity in the bones of horses differed from that in foals, in which the fibers were more delicate and frequency of occurrence was lower. In horses, innervation with CGRP and SP fibers was more dense in the periphery of the bone, whereas in foals, local difference in innervation of the bone was not evident. With the exception of the intersesamoidean ligament, ligaments were more richly innervated than was bone.


CONCLUSIONS
Presence of the nociceptive peptides CGRP and SP indicated that the PSB and, more practically, the adjacent ligaments are sensitive structures.
Cornelissen
B P
BP
Department of General and Large Animal Surgery, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Buma
P
P
Rijkenhuizen
A B
AB
Barneveld
A
A
D000375:Aging; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D005260:Female; D005552:Forelimb / Q000294:innervation; D006736:Horses / Q000033:anatomy & histology*; D007124:Immunoenzyme Techniques / Q000662:veterinary; D008297:Male; D009412:Nerve Fibers / Q000737:chemistry*; D011817:Rabbits; D012716:Sesamoid Bones / Q000294:innervation*; D013373:Substance P / Q000032:analysis*; D013564:Sympathetic Nervous System / Q000737:chemistry; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis
D013373:Substance P; D014446:Tyrosine 3-Monooxygenase; D015740:Calcitonin Gene-Related Peptide