Axotomy Induces Fusimotor-free Muscle-spindles In Neonatal Rats

Axotomy Induces Fusimotor-free Muscle-spindles In Neonatal Rats

Kucera J; Walro J

Neuroscience Letters

1992

1992-03

Crushing the nerve to the medial gastrocnemius (MG) muscle at birth and administering nerve growth factor to rats afterwards results in a reinnervated muscle with supernumerary muscle spindles, some of which must have formed de novo. Structure and innervation of spindles in the reinnervated MG muscles were studied in serial 1-mu-m transverse sections. Two types of spindle-like encapsulations were observed. The prevalent type consisted of one to three small diameter intrafusal fibers with features of nuclear chain fibers or infrequently a nuclear bag fiber. The second type of encapsulation consisted of the small-diameter fibers located in a compartment which abutted a compartment containing a large diameter extrafusal fiber. All intrafusal fibers in spindles of the experimental muscles were innervated by afferents, but most of them (85%) were devoid of efferent innervation. Thus, immature fusimotor neurons may be more susceptible than spindle afferents to cell death after axotomy at birth.

fibers; fusimotor system; intrafusal; intrafusal muscle fiber; nerve; Neurosciences & Neurology; spindle development

Journal Article or Conference Abstract Publication

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