Interactions between motoneurones and muscles in respect of the characteristic speeds of their responses

Abstract

In the preceding paper (Buller, Eccles & Eccles, 1960) evidence was presented which suggested that the differentiation of slow muscles of the cat hind limb to a large extent failed to occur after certain operative procedures on the spinal cord. This finding indicates that in some way the central nervous system controls muscle differentiation. A more analytic investigation into this postulated influence of nerve on muscle has been accomplished by dividing and cross-uniting nerves to fast and slow muscles, so that motoneurones formerly innervating the fast muscle come to innervate the slow muscle by virtue of the regenerative outgrowth of their fibres, and vice versa for the motoneurones of the slow muscle. The effect of this crossed innervation on the speed of muscle contraction has been tested at varying times after the cross-union. These investigations have also been carried out on animals subjected to the operative procedures on the spinal cord, as previously described (Buller et al. 1960). Cross-union experiments allow in addition an investigation into the possible effects in the reverse direction, i.e. of speed of muscle contraction on the conduction velocity of the axons and the after-hyperpolarization of the motoneurones which innervate it. A preliminary account of part of this investigation has already been published (Bulier, . METHODSMost of the cross-union operations have been performed on kittens 2-3 weeks old, but some operations had a wide age dispersion: on kittens as young as 6 days; on kittens from 3 weeks to 4 months; and on full-grown cats at least 6 months old. The operations were performed on anaesthetized animals with full aseptic precautions. Usually the cross-union has been effected between the nerves to soleus and flexor digitorum longus muscles (FDL), but there have also been cross-union experiments between the nerves to peroneal muscles and soleus and between the nerves to gracilis and crureus. The position of the nerve suture has been as far distal as possible from the locus of the nerve cross and as far as possible

Uniformity of metabolic enzymes within individual motor units

“…These and other biochemical characteristics are known to be regulated by the functional demands imposed on the muscle by means of its innervation (e.g., Buller et al, 1960;Vrbova et al, 1978). Implicit in the idea originally formulated by Sherrington (1925), that the motor unit forms the smallest functional component of skeletal muscle controlled by the nervous system, is the concept of biochemical uniformity among the unit's muscle fibers.…”

Trophic effects on the contractile and histochemical properties of rat soleus muscle

“…The cross-rernnervation experiments of Buller et al (1960) and others (Buller et al, 1969;Close, 1969;Bagust et al, 1981;Chan et al, 1982) demonstrated that the motoneuron regulates a variety of contractile, biochemical, and histochemical properties of skeletal muscle. The signals responsible for this muscular plasticity were hypothesized to derive from newly directed activity patterns and/or the supply of a neurotrophic substance to the muscle by the innervating nerve (Buller et al, 1960).…”

“…The signals responsible for this muscular plasticity were hypothesized to derive from newly directed activity patterns and/or the supply of a neurotrophic substance to the muscle by the innervating nerve (Buller et al, 1960).…”

Afferent influences on brain stem auditory nuclei of the chicken: Neuron number and size following cochlea removal

“…Alternatively, innervation of targets by nerves with properties different from those of the normal afferent can lead to functional and biochemical modifications in the postsynaptic target (Buller et al, 1960;Streter et al, 1975;reviewed in Close, 1969). While these findings suggest that synaptic inputs play a crucial role in shaping and maintaining target structures, they do not indicate what signals underlie these regulatory properties.…”