Evaluation of tachykinins and their receptors to determine sensory innervation in the dorsal hoof wall and insertion of the distal sesamoidean impar ligament and deep digital flexor tendon on the distal phalanx in healthy feet of horses.

This research explores the presence of certain neurochemicals and their receptors in different parts of the horse’s hoof. The findings suggest these neurochemicals help control blood flow in these regions.

Introduction

The focus of the research is to evaluate the presence and role of two specific molecules, substance P and neurokinin A, and their receptors in the horse’s foot. These molecules, also referred to as tachykinins, play a crucial role in the nervous system and are actively involved in controlling blood flow.

Methodology

• The study used the feet of 18 healthy horses for the examination. Specific areas of interest were the dorsal hoof wall and the insertion of the distal sesamoidean impar ligament (DSIL) and deep digital flexor tendon (DDFT).
• Samples from the areas of interest were processed for immunocytochemical analysis using rabbit-derived antibodies for substance P and neurokinin A.
• In addition, tissue sections from 8 feet were tested with 125-labeled substance P to identify the location of the tachykinin receptors and confirm their specificity. Surplus nonradioactive substance P was used to label parts where nonspecific binding happened.

Results

• The research findings demonstrated a substantial presence of nerves reactive to substance P and neurokinin A in the DSIL and DDFT insertion region and the associated microvasculature and arteriovenous complexes (AVC).
• These nerves and tachykinin receptors were also found to be abundant in the microvasculature of the dorsal hoof wall. Neurokinin 1 receptors were specific to the microvessel areas in both insertion and hoof wall zones.

Conclusions

• The outcomes of the research document a rich network of nerves and specific receptors for tachykinins in the microvasculature of the horse’s foot.
• The distribution of these receptors in the vascular system indicates that they act as a significant vasodilatory mechanism, i.e., they assist in widening blood vessels to control blood flow in the DSILDDFT insertion area and dorsal hoof wall.