Substance P and calcitonin gene-related peptide-like immunoreactive nerve fibers in lungs from adult equids.

This research investigates the distribution and potential function of substance P and calcitonin gene-related peptide, two neuropeptides, within healthy lungs of adult horses. The study highlights that these nerves, well distributed in the lungs, could perceive inhaled agents and participate in the lungs’ reaction to irritants.

Methods and Findings

• The investigators studied the distribution of two types of nerve fibers (substance P and calcitonin gene-related peptide) in healthy equid (horse family) lungs. They used a method called immunohistochemistry, which relies on antibodies to bind and highlight specific proteins—in this case, the target nerve fibers.
• They found that substance P and calcitonin gene-related peptide-like nerve fibers are not evenly distributed— instead, they are most frequently observed near the lung’s hilus than in caudal lobes or the lung’s periphery.
• The researchers also noted a significant presence of these types of nerve fibers in the lamina propria of the trachea and larger airways, mostly within and directly beneath the airway epithelium. These nerve fibers were also commonly associated with bronchial and pulmonary vessels.

Interpretation and Implications

• The researchers interpreted the presence of substance P and calcitonin gene-related peptide-like nerve fibers in peribronchial neural ganglia as indicating the potential of these nerves to modulate parasympathetic regulation of lung function. The parasympathetic nervous system plays a leading role in rest, digestion and repairing the body, among other physiological processes.
• Given their location, these nerve fibers endowed with substance P or calcitonin gene-related peptide might be well placed to detect inhaled agents. Therefore, these could contribute to the lungs’ response to irritants and pathogens.
• The study thus enhances our understanding of how the nervous system may interact with and influence the respiratory system within the equid family. This knowledge could be crucial for understanding how the respiratory system reacts to different conditions, such as diseases or exposure to irritants.