Presentation on theme: "Drugs affecting neuromuscular transmission Professor Ian Hughes, 9.83; motor nerve - skeletal (striated) muscle ONLY single long."— Presentation transcript:
Drugs affecting neuromuscular transmission Professor Ian Hughes, 9.83; motor nerve - skeletal (striated) muscle ONLY single long cell from CNS; action potential (Na channels) invades terminal opening Ca channels; intracellular Ca rises; vesicles release ACh by exocytosis; diffusion to receptors (ligand operated ion channel [2xalpha,beta,gamma,delta]); Na flows out; depolarisation of endplate; if sufficient depolarisation then voltage operated Na channels open and a propogated action potential followed by contraction results in muscle.
action potential calcium entry Ca++ choline recapture ACh (10,000) in vesicle choline acetylase R acetylcholine esterase ACh Choline pre- synaptic receptors + - diffusion
Uses of neuromuscular blockers entubation - fast and short action relaxation during surgery - long action, reversible, controlled soften electro-convulsive therapy - short and fast action (use with anaesthetic) special conditions - renal or hepatic failure; manipulations; exceptionally convulsions.
Drugs suxamethonium - (Scoline); depolariser; short (3-10min); scoline pains and muscle damage; K+ levels increased; dysrhythmias; hydrolysed by esterases (defect). decamethonium - initial depolarising, later competitive characteristics; longer lasting. dantroline - acts to inhibit Ca++ release in muscle; used in malignant hyperthermia and severe muscle spasm.