Acetylcholine receptor concentration in the mimic musculature of the rat following denervation and reinnervation.

The facial musculature of the rat was denervated by cutting the facial nerve. Over a period of 41 days no facial movements were observed. Acetylcholine receptor concentrations, determined by [125I]-alpha-bungarotoxin binding, increased sharply in the early stage of denervation (at day 10) and were still significantly higher than in the controls after 41 days. When cutting of the facial nerve was followed by immediate nerve repair (primary suture), facial movements returned on about day 16. The receptor concentrations reflected changes monitored by clinical observations. At day 10, when denervation of the facial muscles was still complete, receptor concentrations corresponded to those found in the permanently denervated muscles. At day 16 the reinnervated muscles of half the animals displayed muscle activity and had receptor concentrations identical to those found for normal (control) tissue. The other half of the animals, with no muscular activity detectable, had receptor concentrations as high as in permanently denervated tissue. After 23 days the receptor concentrations had essentially decreased to control levels and all rats had regained complete facial function.