Dexamethasone Induces nAChRs Upregulation in C₂C₁₂ Mouse Myotubes

Abstract

It has been anecdotically observed that patients taking long term glucocorticoid and testosterone medication display resistance to the action of non depolarizing neuromuscular blocking agents (NMBAs). So far no definitive answer has been provided regarding the mechanism of the above steroid action, in fact various possibilities are under scrutiny. The ri ght shift of NMBAs dose-response curve, observed in the presence of glucocorticoids, in an “in vitro” animal model (rat phrenic nerve-hemidiaphragm preparation) is considered by Parr et al (1991) and Robinson et al (1992) as due to a presynaptic steroid effect, leading to an increase of acetylcholine (ach) release and thereby to the inhibition of NMBAs. On the other hand more complex picture can be predicted, in fact Kaplan et al (1990) reported that dexamethasone (dex) increases total surface nicotinic ach receptors (nAChRs),as it is assessed by employing 125 I a BuT binding.In other words, steroidal agents, through a genomic action (Power et al 1992),enhance transcription of receptors mRNA.