Differential reaction of fast and slow α‐motoneurones to axotomy

Abstract

SUMMARY1. The properties of medial gastrocnemius (m.g., fast a) and soleus (sol., slow a) motoneurones of the cat were examined with intracellular electrodes 8-119 days after section of the muscle nerves.2. The axonal conduction velocity was significantly decreased in both m.g. and sol. motoneurones after chronic section of the muscle nerves.3. The amplitude of overshoot of action potentials was significantly increased in both m.g. and sol. motoneurones following section of the muscle nerves.4. No significant changes in the resting membrane potential or the input resistance were observed for sol. motoneurones, whereas m.g. motoneurones showed a slight decrease in the resting potential and a slight increase in the input resistance.5. The duration of after-hyperpolarization was significantly decreased in sol. motoneurones, whereas that in m.g. motoneurones remained virtually unchanged or increased slightly following section of the muscle nerves. 6. The changes described above were not seen in the preparations examined 29-46 days after section of the lumbosacral dorsal roots, suggesting that alterations in the motoneurone properties observed after section of the muscle nerves resulted from axotomy of the motoneurones rather than from sensory deprivation.7. The differences in electrophysiological properties between m.g. and sol. motoneurones were less prominent in axotomized animals than in control, unoperated cats.8. It is concluded that fast (m.g.) and slow (sol.) cc-motoneurones have qualitatively different properties. A possible 'dedifferentiation' of fast and slow c-motoneurones by axotomy is discussed.

Biologically Engineered Protein-graft-Poly(ethylene glycol) Hydrogels: A Cell Adhesive and Plasmin-Degradable Biosynthetic Material for Tissue Repair

“…Autologous grafts typically originate from the patient's sural nerve (a nerve in the lower leg) or other sensory nerves. Since autografts continue to 15 provide the best clinical results, as a natural biomaterial they are considered the "gold standard" in peripheral nerve repair, and the associated functional losses elsewhere in the body are often regarded as acceptable. Nevertheless, major advances in the understanding of nerve regeneration, in surgical techniques, and in material design are producing ever improving alternatives to autologous nerve grafts.…”

Changes in Na+ Channel Currents of Rat Dorsal Root Ganglion Neurons Following Axotomy and Axotomy-Induced Autotomy

“…Last, changes in the types of channels expressed may reflect an injury-induced de-differentiation process (Cummins and Waxman 1997;Kuno et al 1974;Waxman et al 1994). In other words, "large" cells tend to acquire the characteristics of "small" cells and vice versa.…”

The effects of tetrodotoxin‐induced muscle paralysis on the physiological properties of muscle units and their innervating motoneurons in rat.

“…Czeh and colleagues (Czeh, Gallego, Kudo & Kuno, 1978) demonstrated that tetrodotoxin (TTX)-induced muscle paralysis, like axotomy, resulted in decreased duration of the action potential after-hyperpolarization (AHP) in cat soleus motoneurons, coincident with muscle atrophy, and that stimulation of the motor axons distal to the TTX block prevented these changes. They concluded that 'it is likely that muscle activity is directly or indirectly signalled to the innervating motoneurons through the motor axons' (Czeh et al 1978 (Kuno et al 1974a;Gustafsson & Pinter, 1984), muscle inactivity induced by pharmacological nerve blockade with TTX for similar time periods has resulted in axotomy-like (Munson, Foehring & Sypert, 1985) or normal motoneurons (Webb & Cope, 1992 Gardiner, Favron & Corriveau, 1992;Michel, Cowper, Chi, Manchester, Falter & Lowry, 1994). We chose to measure responses over a 2 week period as this duration of inactivity appears to be sufficient for motoneuron changes to occur (Czeh et al 1978;Munson et al 1985).…”