Biomaterial Database

The effects of strontium and barium ions at synapses in sympathetic ganglia. 1977

E M McLachlan

1. A study has been made of the effects of Sr2+ and Ba2+ ions at synapses in isolated superior cervical ganglia of guinea-pigs. Intracellular recordings of membrane potential were made from ganglion cells in the presence of different concentrations of Ca2+, Sr2+ and Ba2+ ions. 2. The addition of Sr2+ (2-5 mM) caused little change in resting membrane potential; in contrast, Ba2+ (1-6 mM) always depolarized the cells and prolonged the duration of action potentials. 3. The resting frequency of spontaneous miniature excitatory post-synaptic potentials (min. e.p.s.p.s) was briefly accelerated by the addition of either Sr2+ or Ba2+, but subsequently returned to about control levels. 4. Following replacement of Ca2+ by Sr2+, e.p.s.p.s could always be evoked during repetitive stimulation of preganglionic axons at a fixed latency after the nerve impulses ('phasic' transmitter release). Replacement of Ca2+ by Ba2+ produced many asynchronous e.p.s.p.s during trains of impulses ('residual' transmitter release). 5. By analysis of the interaction between Sr2+ and Ca2+, Sr2+ was shown to have a partial agonist action on 'phasic' transmitter release. The same analysis applied to Ba2+ failed to demonstrate either a partial agonist or antagonist action. 6. Both Sr2+ and Ba2+ prolonged e.p.s.p.s. Changes in Sr2+ could mainly be attributed to its effect on cell input resistance; Ba2+ may also prolong the time course of transmitter release. 7. The increased frequency of min. e.p.s.p.s which occurs during repetitive stimulation was potentiated by both Sr2+ and Ba2+, Ba2+ being about twice as potent as Sr2+. This activation of 'residual' transmitter release is independent of the action of these ions on 'phasic' release. 8. It is concluded that the reported maintenance by Ba2+ of acetyl-choline output from perfused ganglia results from the asynchronous release of large numbers of quanta during trains of impulses.

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
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
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
D005725	Ganglia, Autonomic	Clusters of neurons and their processes in the autonomic nervous system. In the autonomic ganglia, the preganglionic fibers from the central nervous system synapse onto the neurons whose axons are the postganglionic fibers innervating target organs. The ganglia also contain intrinsic neurons and supporting cells and preganglionic fibers passing through to other ganglia.	Autonomic Ganglia,Ganglion, Autonomic,Autonomic Ganglion
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000109	Acetylcholine	A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.	2-(Acetyloxy)-N,N,N-trimethylethanaminium,Acetilcolina Cusi,Acetylcholine Bromide,Acetylcholine Chloride,Acetylcholine Fluoride,Acetylcholine Hydroxide,Acetylcholine Iodide,Acetylcholine L-Tartrate,Acetylcholine Perchlorate,Acetylcholine Picrate,Acetylcholine Picrate (1:1),Acetylcholine Sulfate (1:1),Bromoacetylcholine,Chloroacetylcholine,Miochol,Acetylcholine L Tartrate,Bromide, Acetylcholine,Cusi, Acetilcolina,Fluoride, Acetylcholine,Hydroxide, Acetylcholine,Iodide, Acetylcholine,L-Tartrate, Acetylcholine,Perchlorate, Acetylcholine
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
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
D001464	Barium	An element of the alkaline earth group of metals. It has an atomic symbol Ba, atomic number 56, and atomic weight 138. All of its acid-soluble salts are poisonous.
D013324	Strontium	An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.