Motor innervation and acetylcholine receptor distribution of human extraocular muscle fibres.

Motor innervation and acetylcholine receptor distribution of human extraocular muscle (EOM) fibres were investigated by using combined silver and acetylcholinesterase (AChE) staining method and [125I]alpha-bungarotoxin autoradiography. Three types of motor endplates were distinguished; (A) a large compact ending on a large-diameter fibre, (B) several endings regularly spaced on an intermediate-diameter fibre, each of which consisted of small stained particles and (C) numerous small endings scattered as a chain of beads on a small-diameter fibre. Type A fibre was singly innervated, while type B and C had multiterminal (possibly polyneuronal) innervation. These results indicate that the organization of human EOM endplates is quite different from that of limb muscle endplates and may provide some implications to understand the pathophysiology of the neuromuscular diseases, for example, myasthenia gravis.