Biomaterial Database

Presynaptic calcium currents at voltage-clamped excitor and inhibitor nerve terminals of crayfish. 1996

S N Wright, and M S Brodwick, and G D Bittner

Department of Zoology, University of Texas, Austin 78712, USA.

1. A two-electrode voltage clamp was used to record calcium currents from the excitatory and inhibitory nerve terminals that innervate the crayfish (Procambarus spp.) opener muscle. Other voltage-dependent currents were blocked with tetrodotoxin, 3,4-diaminopyridine, 4-aminopyridine and tetraethylammonium. 2. The presynaptic calcium current at both excitatory and inhibitory synapses was blocked by cadmium and omega-agatoxin IVA but was not affected by omega-conotoxin GVIA, omega-conotoxin MVIIC or nifedipine, suggesting that the calcium currents flow through P-type calcium channels. 3. Current-voltage (I-V) relations at both excitatory and inhibitory synapses are similar, with current activation near -40 mV, peak current near -10 mV and current reversal at membrane potentials greater than +25 mV. I-V relations were scaled along the current axis by partial calcium current blockade with cobalt, suggesting that series resistance and space-clamp errors were small. 4. A subset of terminals on one muscle fibre was locally superfused with a physiological saline containing barium; the rest of the preparation was superfused with a physiological saline containing calcium channel antagonists. Under such conditions the characteristics of the I-V relation were very similar to the I-V relations recorded when the entire preparation was bathed in physiological levels of calcium, suggesting that the space clamp was adequate. 5. Calcium channel activation, as determined from tail current analyses, was similar when the entire preparation was bathed in physiological levels of calcium or if terminals on one muscle fibre were locally superfused with barium. 6. During a 30 ms depolarization, calcium currents inactivated to a greater extent in inhibitory than in excitatory terminals. The inactivation was of small magnitude (< 20%) and was eliminated by intracellular injection of the calcium chelator BAPTA, suggesting that the inactivation was calcium dependent. 7. These data show that biophysical and pharmacological properties of calcium currents at crayfish neuromuscular junctions resemble those found at stellate synapses in squid.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008839	Microelectrodes	Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed)	Electrodes, Miniaturized,Electrode, Miniaturized,Microelectrode,Miniaturized Electrode,Miniaturized Electrodes
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009411	Nerve Endings	Branch-like terminations of NERVE FIBERS, sensory or motor NEURONS. Endings of sensory neurons are the beginnings of afferent pathway to the CENTRAL NERVOUS SYSTEM. Endings of motor neurons are the terminals of axons at the muscle cells. Nerve endings which release neurotransmitters are called PRESYNAPTIC TERMINALS.	Ending, Nerve,Endings, Nerve,Nerve Ending
D009469	Neuromuscular Junction	The synapse between a neuron and a muscle.	Myoneural Junction,Nerve-Muscle Preparation,Junction, Myoneural,Junction, Neuromuscular,Junctions, Myoneural,Junctions, Neuromuscular,Myoneural Junctions,Nerve Muscle Preparation,Nerve-Muscle Preparations,Neuromuscular Junctions,Preparation, Nerve-Muscle,Preparations, Nerve-Muscle
D002121	Calcium Channel Blockers	A class of drugs that act by selective inhibition of calcium influx through cellular membranes.	Calcium Antagonists, Exogenous,Calcium Blockaders, Exogenous,Calcium Channel Antagonist,Calcium Channel Blocker,Calcium Channel Blocking Drug,Calcium Inhibitors, Exogenous,Channel Blockers, Calcium,Exogenous Calcium Blockader,Exogenous Calcium Inhibitor,Calcium Channel Antagonists,Calcium Channel Blocking Drugs,Exogenous Calcium Antagonists,Exogenous Calcium Blockaders,Exogenous Calcium Inhibitors,Antagonist, Calcium Channel,Antagonists, Calcium Channel,Antagonists, Exogenous Calcium,Blockader, Exogenous Calcium,Blocker, Calcium Channel,Blockers, Calcium Channel,Calcium Blockader, Exogenous,Calcium Inhibitor, Exogenous,Channel Antagonist, Calcium,Channel Blocker, Calcium,Inhibitor, Exogenous Calcium
D003035	Cobalt	A trace element that is a component of vitamin B12. It has the atomic symbol Co, atomic number 27, and atomic weight 58.93. It is used in nuclear weapons, alloys, and pigments. Deficiency in animals leads to anemia; its excess in humans can lead to erythrocytosis.	Cobalt-59,Cobalt 59
D003400	Astacoidea	A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.	Astacus,Crayfish,Procambarus,Astacoideas,Crayfishs
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia