NBD-5-acylcholine: fluorescent analog of acetylcholine and agonist at the neuromuscular junction.

AUTOR(ES)

Jürss, R

RESUMO

We have studied the properties of N-7-(4-nitrobenzo-2-oxa-1,3-diazole)-omega-aminohexanoic acid beta-(N-trimethylammonium)ethyl ester, a fluorescent analog of acetylcholine at the cellular level by using pharmacological and electrophysiological techniques and at the molecular level by measuring the kinetics of interaction with solubilized acetylcholine receptor and with acetylcholine esterase (EC 3.1.1.7). The fluorescent drug is a powerful agonist of acetylcholine at the neuromuscular junction and also strongly desensitizes muscle fibers. Interaction with acetylcholine receptor is accompanied by large changes in the drug's fluorescence. From the kinetics of interaction studied by means of a stopped-flow fluorimeter with laser light source, we obtained a second-order forward rate constant in excess of 1 X 10(8) M-1 sec-1 and an initial dissociation rate constant (k1) of 0.5 sec-1 for receptor from Electrophorous electricus. Interaction of this analog with acetylcholine esterase from E. electricus is accompanied by a transient decrease in fluorescence followed by an increase leading to a stable plateau value at a level near the original one. The initial decrease in fluorescence followed second-order kinetics with k2 of the order of 10(9) M-1 sec-1. The slower consecutive reaction which could be blocked by phosphorylation of the esteratic site, was of first order with k1 = 0.05 sec-1.

Documentos Relacionados

• Electrophysiological and chemical determination of acetylcholine release at the frog neuromuscular junction.
• Kinetic parameters for acetylcholine interaction in intact neuromuscular junction.
• The effects of nerve terminal activity on non-quantal release of acetylcholine at the mouse neuromuscular junction.
• The uptake and release of glutamate at the crayfish neuromuscular junction.
• Regulation of single quantal efficacy at the snake neuromuscular junction.