The use of local anaesthetics to produce prolonged motor nerve block in the study of denervation hypersensitivity.

1. Silastoseal cuffs containing 25% and 45% lignocain, 25% marcain and 25% NaCl were placed onto the sciatic nerve. The effects of this on the sciatic nerve as well as the soleus and extensor digitorum longus (EDL) muscles was studied. 2. Cuffs containing local anaesthetics caused both early and late phases of paralysis, cuffs containing NaCl caused only the late phase of paralysis, showing that the late phase of paralysis was not due to the anaesthetic properties of the drugs. The paralysis produced by these procedures was irreversible. 3. Responses to indirect and direct stimulation of soleus and EDL muscles were compared to assess the degree of denervation. In case of cuffs containing 25% marcain and 45% lignocain more than half of the muscle fibres were denervated. 4. Acetylcholine sensitivity was assesses in all experiments. Soleus and EDL muscles from all animals that had cuffed nerves containing either local anaesthetics or 25% NaCl were hypersensitive to ACh. The degree of hypersensitivity could be correlated to the degree of "denervation" as assessed by comparing the directly and indirectly elicited twitch tensions. 5. It was found that the sciatic nerve undergoes degenerative changes when exposed to cuffs containing either local anaesthetics or 25% NaCl.