Sympathetic activation and muscle spindle.

An adrenergic central control on fusimotor activity has been demonstrated since 1954. At peripheral level, a muscle spindle autonomic innervation is not clearly demonstrated in man, but several data seem to suggest a direct autonomic innervation of muscle spindle in cats and rabbits. Data obtained in patients with peripheral adrenergic denervation (Idiopathic Orthostatic Hypotension) suggest a prevalent control of central adrenergic pathways on muscle spindle sensitivity.