Innervation Pattern of Dermal Blood Vessels in the Bovine Claw Shows Functional Adaptation in Different Areas

Abstract

Introduction: The blood circulation in the claw plays an important role in the pathogenesis of claw diseases. The blood vessel diameter is regulated by innervation with different nerve fibre qualities. In case of inflammation or unphysiologically high mechanical load, the delicate balance of vasodilative and vasoconstrictive neurotransmitters seems to be disturbed and may aggravate the alterations. Knowledge about the innervation pattern of the dermal blood vessels could therefore help to understand some aspects in the pathogenesis of claw diseases.Material and Methods: The lateral claws of the hind limb of cows from a local abattoir were examined. Tissue samples were taken from different segments of the claw, fixed and processed for immunohistochemistry. Antibodies against protein gene product 9.5, tyrosine‐hydroxylase, choline acetyltransferase, substance P and calcitonin gene‐related peptide were applied and colocalization studies were carried out. Results were evaluated with a confocal laser scanning microscope.Results: Dermal blood vessels in the claw are surrounded by nerve fibres containing different neurotransmitters. Occurrence and density differ depending on the respective segment. In the bulbar segment, more vasodilative fibres are demonstrable while in the solear segment vasoconstrictive nerve fibres prevail. The highest innervation was found in all segments around specialized sphincteric arteries in the dermis just beneath the dermal surface modification.Conclusion: The innervation pattern in the claw depends on segment‐specific functional demands. The fine‐tuning of the blood flow in the dermal vascular system is mediated by a combination of different nerve fibres that emit vasoactive substances.Acknowledgement: This work was supported by the European Communities under the Lame cow project QLK5‐CT‐2002‐00969.The authors are solely responsible and the work does not necessarily represent the opinion of the European Communities.