Inhibition of the target phenomenon in tenotomized rabbit muscle by medullary lesions

Influence of isaxonine on reinnervation of the rat gastrocnemius muscle

Isaxonine is reported to have a favourable effect on nerve regeneration. The histological and histochemical changes were compared in the gastrocnemius muscles of 20 rats, in which the left sciatic nerve was frozen-crushed for 10 s at the level of the buttock. The animals received a daily dose of intraperitoneal isaxonine and ten others the solvent only. After 8 weeks small type grouping was seen in rats receiving solvent only and large type grouping in rats treated with isaxonine. After 10 weeks a checkerboard pattern of the fibre types was observed in the muscles of animals receiving solvent only but fibre type grouping was present in those treated with isaxonine. This experiment indicates that isaxonine prevents synaptic remodelling by suppression of the redundant nerve endings from additional axons, which have regenerated more slowly, in making contact with motor endplates.

Influence of isaxonine on the target phenomenon, muscle fibre size and neuromuscular junction in the tenotomized and denervated gastrocnemius muscle of the rat

Isaxonine is reported to accelerate the rate of peripheral nerve regeneration, stimulate axonal sprouting and promote motor and sensory function recovery. The target phenomenon in muscle fibers is the morphological expression of increased stretch activity in a diseased muscle. It can be produced in the gastrocnemius muscle of the rat by tenotomy and is inhibited by simultaneous denervation. The influence of isaxonine on this experimental model was studied. Twenty Wistar rats were submitted to bilateral section of the Achilles tendon and section of the left sciatic nerve. In ten rats, treated with isaxonine, the qualitative and quantitative changes in the gastrocnemius muscle were compared with the control group over a period of 3 weeks. No statistical differences were observed in the occurrence and inhibition of the target phenomenon, the muscle fibre size and the neuromuscular junction. Isaxonine has no direct effect on a diseased muscle with an intact nerve supply, nor in the early stages after complete denervation.

Modifications in the histochemical and biochemical changes in tenotomized rat soleus by denervation

Response of tenotomized rat soleus muscle to denervation performed at different time intervals, has been investigated. Tenotomized muscles showed typical central core lesions seven days post-operatively. These were not observed in m-ATPase stained sections of simultaneously denervated and tenotomized muscles, and muscles denervated 24 h after tenotomy. Central core lesions were not prevented in muscles denervated 28 h after tenotomy, indicating that tenotomy effects responsible for central lesions are completed by this time. Myosin light chain pattern of muscles denervated 28 h after tenotomy, and tenotomized only were similar showing increased LC3/LC1 ratio. Simultaneously denervated and tenotomized muscle however showed all the three light chains relatively equal in quantity. The results suggest that elimination of neural activation within 28 h prevents myofibrillar loss and minimized other changes which occur due to tenotomy.

Influence of stretch on the target phenomenon in the tenotomized and immobilized gastrocnemius muscle of the rat

The influence of traction on the target phenomenon was analysed in the tenotomized gastrocnemius muscle of Wistar rats. Target fibres were constantly observed at the medial side of the heads of the non-immobilized and tenotomized gastrocnemius muscles used as control. In the muscles fixed in flexion, no target fibres could be detected, while in the muscles fixed in hyperextension some target fibres were seen. The latter were less numerous than those present in the non-immobilized muscles. This experiment proves the importance of stretch mechanisms in the pathogenesis of the target phenomenon.