Prednisone-neostigmine interactions at cholinergic junctions

Long-term treatment with glucocorticoids increases synthesis and stability of junctional acetylcholine receptors on innervated cultured human muscle

We have studied the effect of long-term treatment with hydrocortisone on the expression of acetylcholine receptors (AChRs) at the neuromuscular junctions of human muscle cultured in monolayer and innervated de novo by fetal rat spinal cord motoneurons. Hydrocortisone increased accumulation of junctional AChRs in a dose- and time-dependent fashion. This increase was due to both decreased degradation and increased synthesis of AChRs. Other glucocorticoids, dexamethasone and prednisolone, exerted similar effects. Our study demonstrates a novel action of glucocorticoids on human junctional AChRs.

A neuromuscular transmission disorder: combined myasthenia gravis and Lambert Eaton syndrome in one patient

The distinction between myasthenia gravis and Lambert Eaton myasthenic syndrome can usually be made by the clinical and neurophysiological features. A patient was observed with features which suggested a combination of both disorders. This has been described in few patients before. The importance of electromyography in both distal and proximal limb muscles for a correct diagnosis is demonstrated. Only in proximal nerve stimulation tests was proof found of the existence of both syndromes.

Favorable results of thymectomy combined with prednisolone alternate-day administration in myasthenia gravis

Administration of anti-cholinesterase before operation and high doses of prednisolone after the operation are commonly prescribed in cases of thymectomy for the treatment of myasthenia gravis. Our policy is to carry out an extended thymectomy combined with pre- and post-operative administration of prednisolone on alternate days. Our method was used in the treatment of 50 patients with generalized myasthenia gravis, from January 1979 to December 1984. The results were examined in conjunction with the necessity for preoperative administration of an anti-cholinesterase preparation and also with factors influencing the follow-up result and postoperative process. This method made it feasible to perform surgery under conditions of stabilization of clinical symptoms and satisfactory postoperative management. A postoperative period of unstable symptoms could thus be avoided. The palliation rate at one year after the operation was 96 per cent, while the remission rate at 5 years after the operation was 70 per cent. The preoperative supplement of anti-cholinesterase and preoperative per cent forced vital capacity were considered to be predictive factors concerning the necessity of artificial respiration.

Influence of neostigmine treatment on embryonic development of acetylcholine receptors and neuromuscular junctions

The postulated role of the acetylcholine receptor in the formation of neuromuscular synapses during the course of embryonic development was investigated in the superior oblique muscle of white Peking duck embryos. The possibility that the number of receptors could be experimentally lowered by chronic injections of the anticholinesterase agent, neostigmine methylsulfate, was determined using 125I-alpha-bungarotoxin. The total number of acetylcholine receptors on incubation day 12, 2 d subsequent to the onset of treatment, was reducted 45% as compared to saline-treated controls. A similar reduction in total receptor content (49%) was also observed on day 19. Radioautographic preparations showed that clusters of acetylcholine receptors were rare and that the grain density of extrajunctional receptors was also reduced. Hence, chronic treatment with neostigimine during development was observed to exert an effect on both the number and distribution of receptors in the developing superior oblique muscle. These changes occurred in the absence of any apparent effect on muscle differentiation in general. Myoblasts and myotubes were present on day 14 and further differentiated into myofibers by day 18 in both neostigmine and saline-treated muscles. The cytology of the develop;ing muscle cells also appeared normal. This is in contradistinction to the striking morphological changes that take place in adult mammalian and avian muscle after anticholinesterase treatment. More significantly, the decreased total receptor content and sparsity of clusters had no apparent effect on the formation of developing neuromuscular junctions at the electron microscopic level. The frequency of neuromuscular junctions in neostigmine-treated muscles was similar to that of the controls. It is concluded that acetylcholine receptor clusters are not required for the events leading to the morphological formation of neuromuscular junctions during in vivo development.

Eaton-Lambert myasthenic syndrome: long-term treatment of three patients with prednisone

Three patients with the myasthenic syndrome of Eaton-Lambert (ELS) were treated with prednisone for 6 and 12 months and more than 3 years, respectively. Muscle strength increased considerably in all, reaching a peak after 3 to 4 months, and was accompanied by simultaneous electromyographic improvement. Reduction of prednisone led to deterioration in all 3 patients; strength was regained when the higher dosage of prednisone was resumed. Prednisone is an alternative form of treatment for ELS, although the mechanism for its action is unclear.

Disorders of neuromuscular transmission other than myasthenia gravis

Disorders of neuromuscular transmission in humans are caused by a wide variety of agents including systemic diseases, drugs, environmental toxins, animal envenomation, cations, and hormones. Some are genetically determined. Many are of known etiology. All such disorders interfere with one or more events in the sequence whereby a nerve impulse excites a muscle action potential. In many disorders of neuromuscular transmission, abnormal fatigue occurs, and some cases respond dramatically to treatment. Investigation of the microphysiology, microanatomy, and pharmacology of both normal and diseased neuromuscular junctions has increased our knowledge of these disorders.