Hiroki Mikami

Histochemical localization and quantitative morphometric analysis of autonomic and sensory nerves in bronchi of two lines of guinea pigs different in bronchial sensitivity to acetylcholine exposure

Abstract The histochemical localization and quantitative morphometric analysis of autonomic and sensory nerves around bronchi were carried out in two lines (bronchial hypersensitive strain; BHS and bronchial hyposensitive strain; BHR) of guinea pigs selectively bred for varying sensitivities to acetylcholine (ACh). Acetylcholinesterase (AChE)-positive nerve fibers, tyrosine hydroxylase (TH)-, calcitonin gene-related peptide (CGRP)- and substance P(SP)-immunoreactive (IR) nerve fibers were found in the lamina propria and smooth muscle layer of bronchi with or without cartilage in two lines. The number per unit area (N a ) and the total length per unit area (L a ) in the lamina propria and smooth muscle layer around bronchi of AChE-positive nerves were greatest in 4 kinds of nerves, while TH-IR nerve had the smallest N a and L a . CGRP- and SP-IR nerves showed intermediate N a and L a compared with the former. AChE-positive nerves were thought to be responsible for bronchial reactivity in 4 kinds of nerves. N a and L a of AChE-positive nerves with cartilage were significantly greater in BHR than in BHS. In addition, BHS showed a tendency to have greater N a and L a of TH-, CGRP- and SP-IR nerves than BHR. It is suggested that the alteration in N a and L a of these nerves, especially AChE-positive nerves, plays an important role in the expression of bronchial hypersensitivity in BHS.