Effects of intra-axonal injection of Ca2+ buffers on evoked release and on facilitation in the crayfish neuromuscular junction.
Ca2+ buffers were injected into the excitatory axon of the crayfish opener muscle. The magnitude and time course of evoked release and of facilitation were measured. EGTA (on-rate about 10(6) M-1S-1) had no effect on evoked release but reduced facilitation. BAPTA and nitr-5, buffers with similar Kd's but faster on-rates, reduced both evoked release and facilitation. However, these buffers had no effect on the time course of evoked release. These results show that fast Ca2+ buffers reduce the Ca2+ transient associated with evoked release and also the level of residual Ca2+ involved in facilitation. However, Ca2+ buffering is not the mechanism which controls the time course of release.
Hochner
B
B
Otto Loewi Center for Cellular and Molecular Neurobiology, Hebrew University of Jerusalem, Israel.
Parnas
H
H
Parnas
I
I
D000818:Animals; D003400:Astacoidea; D002021:Buffers; D002118:Calcium / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D005071:Evoked Potentials; D066298:In Vitro Techniques; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D002021:Buffers; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium