Yl. Shi et al., SELECTIVE-INHIBITION OF THE SLOW K-NERVE ENDING BY PLASMA FROM A MYASTHENIA-GRAVIS PATIENT( CURRENT AT MOTOR), Journal of the neurological sciences, 130(2), 1995, pp. 165-170
The effect of plasma from a myasthenia gravis (MG) patient, containing
anti-presynaptic membrane receptor (PsmR) antibody on the membrane cu
rrents of motor nerve ending was investigated in mouse intercostal ner
ve triangularis sterni preparations by perineurial recording. After in
hibition of both the fast K+ current and Ca2+-dependent K+ current by
30 mM Tetraethyl-ammonium (TEA) unmasked the voltage dependent fast Ca
2+ current and the ''Ca plateau'', which was contributed by the voltag
e-dependent slow Ca2+ current and slow K+ current. Application of the
MG plasma caused further prolongation and increase of the Ca plateau,
due to blockage of the slow K+ current. This effect was observed immed
iately after the application and could be partially reversed by washin
g, whereas no change was found by addition of the plasma from healthy
persons. When K+ current was completely blocked by 30 mM TEA and 300 m
u M 3,4-diaminopyridine (3,4-DAP), the fast Ca2+. current and the slow
Ca2+ current were revealed. Neither the fast nor the slow Ca2+ curren
t could be affected by the MG plasma; It was also shown that the MG pl
asma was devoid of noticeable effect on the voltage dependent Na+ curr
ent, fast K+ current as well as the Ca2+-dependent K+ current. So the
effect of the MG plasma with antibody to PsmR was concluded to inhibit
the slow K+ current selectively. As we knew, the beta-bungarotoxin bi
nding protein was a kind of K+ channel, these results further confirme
d that the beta-bungarotoxin binding protein should be the target of t
he antibody to PsmR found in the plasma of some patients suffering fro
m MG.