title: Identifications of the intrafusal endings of skeletofusimotor axons in the cat.
abstract: Direct identification of the endings of skeletofusimotor (beta) axons has been made in muscle spindles deprived for their gamma innervation by degeneration. Hindlimb muscles were prepared in which 1--5 fast-conducting motor axons were left intact while the rest of the motor supply was cut and allowed to degenerate for a period of 7 days. In 3 experiments a single beta axons survived supplying tenuissimus, and in 2 experiments beta axons were among 4 or 5 surviving axons that supplied superficial lumbrical and abductor digiti quinti medius muscles. Motor endings identified as p1 plates were found in teased, silver preparations of all experimental muscles, a total of 35 such plates being located in 15 spindles. The plates were all supplied to bag1 fibres. The experiments show that if a spindle innervated by a beta axon is deprived of its gamma supply by degeneration the motor endings that remain intact are p1 plates.
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure; D002415:Cats; D004558:Electric Stimulation; D005071:Evoked Potentials; D006614:Hindlimb / Q000294:innervation; D009045:Motor Endplate / Q000033:anatomy & histology / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology* / Q000648:ultrastructure; D009047:Motor Neurons, Gamma / Q000502:physiology; D009470:Muscle Spindles / Q000033:anatomy & histology / Q000502:physiology*; D009132:Muscles / Q000294:innervation*; D009410:Nerve Degeneration; D009431:Neural Conduction