Differences between foreign and original innervation of skeletal muscle in the frog

Abstract

SUMMARY1. In order to investigate the characteristics of synapses formed by a foreign nerve in skeletal muscle of the frog, the hypoglossal nerve in Rana pipiens was implanted under the cutaneus pectoris (c.p.) muscle which was denervated 1 month later. .multiphasic e.p.p.s whereas these were only seen on original nerve stimulation during the first 3 months after regeneration. These abnormalities of the foreign innervation persisted for at least 6 months after crushing the original nerve. 4. The geniohyoid muscle (which is normally innervated by the hypoglossal nerve) and c.p. appear to contain similar types of muscle fibre. Furthermore, when the geniohyoid muscle became reinnervated by the hypoglossal nerve after it had been crushed, the synapses formed were more effective than those formed by the hypoglossal nerve in c.p.5. Even if reinnervation of c.p. by its nerve was delayed by cutting the brachial nerve at its exit from the vertebral column, the synapses formed by the hypoglossal nerve in c.p. remained abnormal, suggesting that an incompatability exists between the c.p. muscle and the hypoglossal nerve.6. In spite of the differences found between the synapses formed by the hypoglossal nerve and the original nerve in c.p., there was no evidence of regression of the hypoglossal innervation during the period of observation.

Accuracy of reinnervation of rat internal intercostal muscles by their own segmental nerves

“…In contrast with those of adult mammals, adult urodele motor axons show a strong preference for their own muscle (Grimm,197 1). Anuran motoneurons, too, can show a marked ability to find their correct muscles when sectioned at very early stages (Fare1 and Bemelmans, 1985) and can show some selectivity during reinnervation in the adult (Sayers and Tonge, 1982).…”

A study of factors influencing synapse formation by a foreign nerve in skeletal muscle of Rana pipiens.

“…regenerated within the neural tubes of the degenerated c.p. nerve were significantly more efficient than those formed in a previous study (Sayers & Tonge, 1982) when axons from the h.n. grew across the muscle fibres, suggesting that the pathway taken by the axons might influence the efficacy of the synapses formed.…”

“…in 198 fibres was 49-5 (± 274) and this value, which is significantly lower than in normal c.p. (123-5) or geniohyoid muscles (915; Sayers & Tonge, 1982) showed only a slight increase during the 6 month observation period (Fig. 4) H.n.…”

“…stimulation and the e.p.p.s evoked in one of the arm muscles (2-4+0-18 ms) and to the latency observed during stimulation of the regenerated c.p. nerve (3 3 ms) in its own muscle (Sayers & Tonge, 1982).…”

“…In the mammal regenerating axons reinnervate skeletal muscle in an apparently random manner (Sperry, 1941;Bernstein & Guth, 1961) while in the urodele axons appear able to reinnervate their appropriate target tissues selectively (Grimm, 1971;Cass, Sutton & Mark, 1973;Cass & Mark, 1975;Genat & Mark, 1977;Holder, Tonge & Jesani, 1984). In adult anurans, regenerating motor axons innervate skeletal muscle non-selectively (Hoh, 1971) but the synapses formed by inappropriate axons in a particular muscle release less acetylcholine per nerve impulse (as estimated from the mean quantal content of end-plate potentials) than those formed by the appropriate nerve (Sayers & Tonge, 1982). The inappropriate synapses also showed an increased latency between nerve H. SA YERS AND D. A. TONGE stimulation and the onset of the end-plate potentials (e.p.p.s) and an increase in polyneuronal innervation of individual muscle fibres.…”