TOPOGRAPHY OF MECHANORECEPTORS IN THE SHOULDER JOINT REGION - A COMPUTER-AIDED 3D RECONSTRUCTION IN THE LABORATORY MOUSE

Background: We investigated the pattern of distribution of corpuscular sensory nerve endings in the shoulder region of the laboratory mouse in relation to their functional properties, Methods: Twelve adult fema le white NMRI-Fa-mice were used, The topography of sensory nerve endin gs in the shoulder joint region was reconstructed by three-dimensional image processing by using serial silver-stained sections of paraffin- embedded samples, Semithin sections obtained from additional samples w ere used for light microscopy. Results: Within the fibrous layer of th e joint capsule, three types of mechanoreceptors were identified: smal l lamellated corpuscles of the Pacini type, Ruffini corpuscles, and Go lgi tendon organs, Intracapsular small lamellated corpuscles of the Pa cini type (in an average number of 29/joint) were found mainly in thre e areas: in the predominantly flaccid tissue of the axillary region, i n the denser ventromedial parts of the capsule, close to the scapula, and in the tight texture of the fiber bundles near the glenoid labrum, Ruffini corpuscles were identified only in small numbers (2/joint) in the ventral aspect of the articular capsule of two animals, Golgi ten don organs (14 or 15 receptors/joint) were discovered predominantly in close vicinity to the joint capsule at the muscle tendon junction of the inserting rotator cuff muscles and in the biceps brachii and trice ps brachii muscles, Conclusions: In view of their location in the shou lder joint capsule and the glenoid labrum, corpuscular mechanoreceptor s evidently play an important role in joint control by inducing protec tive reflex actions in phases of extreme or abnormal movement, The den sity of sensory receptors in distinct areas of the shoulder joint caps ule appears to be related to zones that are subjected to increased bio mechanical stress during physical activity. (C) 1997 Wiley-Liss, Inc.