Guanidine and Neuromuscular Transmission

Abstract

The effect of guanidine on the neuromuscular transmission in human intercostal and mouse diaphragm muscle in vitro during repetitive nerve stimulation was studied. The drug greatly increased the release of acetylcholine (ACh) quanta by nerve impulses at low frequencies of nerve stimulation and at the beginning of tetani at high frequencies of stimulation. The effect was shown to be produced by an increase in fractional release from an unchanged store of ACh quanta available fro immediate release. This seems to explain why guanidine has a poor therapeutic effect in myasthenia gravis but a good effect in the myasthenic syndrome.

Cannabinoid-induced increase of quantal size and enhanced neuromuscular transmission

“…Inhibition of the AEA-degrading enzyme FAAH likewise elevated mEPP amplitude, suggesting that endogenous cannabinoids can regulate quantal size at the NMJ. During tetanic activation of muscle there is a decline in quantal content/number, which can be a challenge to effective neuromuscular transmission 28 , 29 . Interestingly, blood concentrations of AEA increase after athletes exercise 30 , 31 .…”

Effects of 4‐aminopyridine on Statistical Parameters of Transmitter Release at the Neuromuscular Junction

“…Quantitative estimation of the effect of4-AP on the quantum content of epps (m) showed that the drug increases the number of transmitter packages released by each nerve impulse. 4-AP enhances m by increasing the binomial parameter n and not p. In this respect 4-AP resembles tetraethylammonium and guanidine (Volle & Branisteanu 1976) which also increase evoked transmitter release from motor nerves (Otsuka & Endo 1960;Kamenskaya et a/. 1975).…”

Loss of MUNC13-1 function causes microcephaly, cortical hyperexcitability, and fatal myasthenia

“…The miniature endplate (EP) potential (MEPP), and EP potential (EPP) amplitudes and the number of quanta released by nerve impulse ( m ) were measured as previously reported. 14 – 16 The number of readily releasable quanta ( n ), estimates of the probability of quantal release ( p ), 17 and the EP acetylcholine receptor (AChR) content were determined as previously described. 18 …”