Biomaterial Database

Tonic release of transmitter at the neuromuscular junction of the crab. 1975

I Parnas, and R Rahamimoff, and Sarney

1. Synaptic transmission was studied at the neuromuscular junction of the crab Ocypoda cursor, using conventional electrophysiological technique. 2. It was found that fibres of the extensor muscle and those composing the internal layer of the closer muscle have only post-synaptic inhibition (S fibres) while the fibres at the external layer of the closer muscle have in addition presynaptic inhibition (R fibres). 3. In S fibres, addition of GABA reduces input membrane resistance (Rm) and e.p.s.p. amplitude approximately to the same degree. The effect shows desensitization. In R type fibres, GABA reduces the e.p.s.p. much more than expected from changes in Rm. The post-synaptic effect of GABA on Rm shows desensitization, while the presynaptic effect does not show desensitization. 4. In about 50 percent of the cases, after desensitization occurred, Rm increased by about 10-30 percent above the control. Similar increase in Rm occurred after application of picrotoxin. These results suggest that initially the membrane resistance was lower due to tonic release of inhibitory transmitter. 5. The Q10 of Rm was found to vary between 2 and 3. In Ca2+ free media, Cl- free media, or in picrotoxin the Q10 is about 1-3. 6. In R fibres, addition of picrotoxin increased the amplitude of the e.p.s.p. by 30-60 percent above the expected increase due to changes in Rm. 7. In S fibres the mean slope of log e.p.s.p. vs. log [Ca2+] was found to be 1-63, while in R fibres the slope was 0-93. These results suggest the presence of tonic release of the inhibitory transmitter which acts both post-synaptically and presynaptically.

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
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009433	Neural Inhibition	The function of opposing or restraining the excitation of neurons or their target excitable cells.	Inhibition, Neural
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
D010852	Picrotoxin	A mixture of PICROTOXININ and PICROTIN that is a noncompetitive antagonist at GABA-A receptors acting as a convulsant. Picrotoxin blocks the GAMMA-AMINOBUTYRIC ACID-activated chloride ionophore. Although it is most often used as a research tool, it has been used as a CNS stimulant and an antidote in poisoning by CNS depressants, especially the barbiturates.	3,6-Methano-8H-1,5,7-trioxacyclopenta(ij)cycloprop(a)azulene-4,8(3H)-dione, hexahydro-2a-hydroxy-9-(1-hydroxy-1-methylethyl)-8b-methyl-, (1aR-(1aalpha,2abeta,3beta,6beta,6abeta,8aS,8bbeta,9S))-, compd. with (1aR-(1aalpha,2abeta,3beta,6beta,6abeta,8,Cocculin
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003386	Brachyura	An infraorder of chiefly marine, largely carnivorous CRUSTACEA, in the order DECAPODA, including the genera Cancer, Uca, and Callinectes.	Blue Crab,Callinectes sapidus,Carcinus maenas,Crab, Blue,Crab, Common Shore,Crab, Green,Crabs, Short-Tailed,Crabs, True,Green Crab,Uca,Common Shore Crab,European Shore Crab,Blue Crabs,Brachyuras,Carcinus maena,Common Shore Crabs,Crab, European Shore,Crab, Short-Tailed,Crab, True,Crabs, Blue,Crabs, Common Shore,Crabs, Green,Crabs, Short Tailed,Green Crabs,Shore Crab, Common,Shore Crab, European,Shore Crabs, Common,Short-Tailed Crab,Short-Tailed Crabs,True Crab,True Crabs,Ucas,maenas, Carcinus
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.
D005680	gamma-Aminobutyric Acid	The most common inhibitory neurotransmitter in the central nervous system.	4-Aminobutyric Acid,GABA,4-Aminobutanoic Acid,Aminalon,Aminalone,Gammalon,Lithium GABA,gamma-Aminobutyric Acid, Calcium Salt (2:1),gamma-Aminobutyric Acid, Hydrochloride,gamma-Aminobutyric Acid, Monolithium Salt,gamma-Aminobutyric Acid, Monosodium Salt,gamma-Aminobutyric Acid, Zinc Salt (2:1),4 Aminobutanoic Acid,4 Aminobutyric Acid,Acid, Hydrochloride gamma-Aminobutyric,GABA, Lithium,Hydrochloride gamma-Aminobutyric Acid,gamma Aminobutyric Acid,gamma Aminobutyric Acid, Hydrochloride,gamma Aminobutyric Acid, Monolithium Salt,gamma Aminobutyric Acid, Monosodium Salt
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