Studies on the neuromuscular junction with a special preference to nicotinic receptors in normal delivering cows and cows suffering from parturient paresis.

Acetylcholine synthesizing (ACh-s) activity, and binding of 3H-alpha-bungarotoxin (3H-Btx) and 3H-d-tubocurarine (3H-TC) were analysed in gluteus media muscle from normal cows and from cows suffering from parturient paresis, both at parturition and 3 months later. At parturition, the ACh-s activity was 50% lower in the muscle of paretic cows than in non-paretic cows. No difference was found in the number of 3H-Btx and 3H-TC binding sites at parturition, while 3 months after parturition the numbers of 3H-TC and 3H-Btx binding sites were significantly higher in normal than in paretic cows. These significant differences in the number of receptors and a possible underlying receptor regulation defect might be a plausible etiological factor for the disease parturient paresis.