Cooperative Ca2+ Removal from Presynaptic Terminals of the Spiny Lobster Neuromuscular Junction

1. We studied the blocking properties of a spider (Nephila clavata) toxin (JSTX) purified from venom on the spiny lobster neuromuscular junction. 2. When a small amount of JSTX was applied to the neuromuscular junction, the excitatory postsynaptic potential (EPSP) was partially suppressed. The amplitude of EPSPs remained at a steady level for several hours during the washing of the preparation, showing that the action of JSTX is irreversible. 3. We recorded the excitatory postsynaptic current (EPSC) from synaptic site using a macro-patch electrode. The amplitude of EPSC increased linearly with hyperpolarization of the membrane potential in the presence and absence of JSTX. 4. The decay phase time constant of EPSC and spontaneous EPSC was decreased by hyperpolarizing the membrane potential both in the absence and in the presence of JSTX. The relationship between the decay time constant and the membrane potential was not modified by JSTX. 5. It is suggested that JSTX irreversibly blocks EPSC by acting on the site that is apart from the ionic channel of the glutamate receptor molecule.

Download Full-text

Electrophysiological events recorded at presynaptic terminals of the crayfish neuromuscular junction with a voltage indicator

The Journal of Physiology ◽

10.1113/jphysiol.2008.158089 ◽

2008 ◽

Vol 586 (20) ◽

pp. 4935-4950 ◽

Cited By ~ 9

Author(s):

Jen-Wei Lin

Keyword(s):

Neuromuscular Junction ◽

Presynaptic Terminals ◽

Crayfish Neuromuscular Junction ◽

Voltage Indicator

Download Full-text

Ca2+ dynamics of the presynaptic nerve terminal and short-term plasticity at the spiny lobster neuromuscular junction

Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology ◽

10.1016/s1095-6433(99)90558-5 ◽

1999 ◽

Vol 124 ◽

pp. S141

Author(s):

H Kijima ◽

K Ohnuma ◽

S Ogawa ◽

T Takeuchi ◽

N Suzuki

Keyword(s):

Neuromuscular Junction ◽

Nerve Terminal ◽

Spiny Lobster ◽

Short Term ◽

Presynaptic Nerve Terminal ◽

Short Term Plasticity

Download Full-text

Facilitation of neurotransmitter release at the spiny lobster neuromuscular junction

Neuroscience Research ◽

10.1016/s0168-0102(00)00099-7 ◽

2000 ◽

Vol 37 (1) ◽

pp. 33-48 ◽

Cited By ~ 4

Author(s):

Shun-ichi Ogawa ◽

Tomoyasu Takeuchi ◽

Kiyoshi Ohnuma ◽

Naoya Suzuki ◽

Akiko Miwa ◽

...

Keyword(s):

Neuromuscular Junction ◽

Neurotransmitter Release ◽

Spiny Lobster

Download Full-text

Calcium-activated potassium conductance in presynaptic terminals at the crayfish neuromuscular junction.

The Journal of General Physiology ◽

10.1085/jgp.98.6.1161 ◽

1991 ◽

Vol 98 (6) ◽

pp. 1161-1179 ◽

Cited By ~ 25

Author(s):

S Sivaramakrishnan ◽

G D Bittner ◽

M S Brodwick

Keyword(s):

Neuromuscular Junction ◽

Potassium Conductance ◽

Presynaptic Terminal ◽

Constant Current ◽

Delayed Rectifier ◽

Presynaptic Terminals ◽

Potassium Conductances ◽

Constant Current Pulse ◽

Calcium Activated Potassium Conductance ◽

Tetraethylammonium Ions

Membrane potential changes that typically evoke transmitter release were studied by recording intracellularly from the excitor axon near presynaptic terminals of the crayfish opener neuromuscular junction. Depolarization of the presynaptic terminal with intracellular current pulses activated a conductance that caused a decrease in depolarization during the constant current pulse. This conductance was identified as a calcium-activated potassium conductance, gK(Ca), by its disappearance in a zero-calcium/EGTA medium and its block by cadmium, barium, tetraethylammonium ions, and charybdotoxin. In addition to gK(Ca), a delayed rectifier potassium conductance (gK) is present in or near the presynaptic terminal. Both these potassium conductances are involved in the repolarization of the membrane during a presynaptic action potential.

Download Full-text

Na+ current in presynaptic terminals of the crayfish opener cannot initiate action potentials

Journal of Neurophysiology ◽

10.1152/jn.00959.2015 ◽

2016 ◽

Vol 115 (1) ◽

pp. 617-621 ◽

Cited By ~ 3

Author(s):

Jen-Wei Lin

Keyword(s):

Patch Clamp ◽

Neuromuscular Junction ◽

Action Potential ◽

Action Potentials ◽

Peak Amplitude ◽

High Threshold ◽

Na Current ◽

Presynaptic Terminals ◽

Activation Rate ◽

Fast Activation

Action potential (AP) propagation in presynaptic axons of the crayfish opener neuromuscular junction (NMJ) was investigated by simultaneously recording from a terminal varicosity and a proximal branch. Although orthodromically conducting APs could be recorded in terminals with amplitudes up to 70 mV, depolarizing steps in terminals to −20 mV or higher failed to fire APs. Patch-clamp recordings did detect Na+ current ( INa) in most terminals. The INa exhibited a high threshold and fast activation rate. Local perfusion of Na+-free saline showed that terminal INa contributed to AP waveform by slightly accelerating the rising phase and increasing the peak amplitude. These findings suggest that terminal INa functions to “touch up” but not to generate APs.

Download Full-text