Properties of Golgi-Mazzoni afferents in cat knee joint capsule, as revealed by mechanical studies of isolated joint capsule.

Abstract

Sensory neurons innervating joint capsule receptors were studied using isolated, innervated sections of joint capsule from the region of the cat knee innervated by the medial articular nerve, subjected to controlled loadings. Most afferents were not activated by in-plane stretching of the capsule. All afferents were readily activated when the inside surface of the capsule was compressed with a probe. Compressing the outside surface did not activate afferents. Stress analysis revealed that the receptors resided along the inside surface of the capsule. Frequency of afferent discharge was linearly related to compressive stress in a direction perpendicular to the plane of the specimen. Histological studies of capsule sections revealed that the region of capsule studied contains, almost exclusively, thinly encapsulated endings of the Golgi-Mazzoni type located along the inside surface of the capsule. Golgi-Mazzoni endings in joint capsule are slowly adapting receptors which by virtue of their location along the inside surface of the capsule, are sensitive to compression in a plane perpendicular to the plane of the capsule but not to tensional loading in the plane of the capsule.