Occurrence of capillaries with fenestrae in the intrinsic laryngeal muscles of the guinea pig after unilateral denervation.

Capillaries in the posterior cricoarytenoid and the arytenoid muscles of the guinea pig were examined by electron microscopy 3 days after transection of unilateral recurrent laryngeal nerve. The denervated posterior cricoarytenoid muscle had neuromuscular junctions (NMJs) lacking terminal axons, while in the unpaired arytenoid muscle, normal and denervated NMJs coexisted among muscle fibres being seemingly normal. Capillaries in both muscles were almost of the continuous type. However, approximately 10% of capillaries around the denervated NMJs and among some muscle fibres in both muscles, often had a small number (< 10) of fenestrae bridged by a single-layered diaphragm. The untreated normal muscles contained only continuous capillaries. These findings suggest that denervation may induce the fenestrated changes of intramuscular capillaries.