Problems associated with the use of tetraethylammonium to test for monosynaptic connexions

1975 ◽  
Vol 62 (3) ◽  
pp. 797-803
Author(s):  
M. S. Berry ◽  
V. W. Pentreath
Keyword(s):  
Nervous System ◽  
Transmitter Release ◽  
Gastropod Mollusc ◽  
Postsynaptic Response ◽  
Postsynaptic Potential ◽  
Planorbis Corneus

Several investigators of the molluscan nervous system have used TEA, injected into presynptic neurones, to determine whether the connexions made by these neurones are monosynaptic. The increase in spike duration produced by the TEA causes an increase in transmitter release, and hence an increase in the amplitude of the postsynaptic potential if the connexion is direct. If the connexion is indirect, the spike in an intercalated neurone will not be affected by the TEA, and the postsynaptic response will remain constant. Experiments described here show that TEA can cross electrotonic junctions in the gastropod mollusc Planorbis corneus. They also show that each TEA-prolonged presynaptic impulse may produce more than one postsynaptic impulse. A larger postsynaptic potential could therefore be produced by presynaptic injection of TEA in the case of an indirect connexion. This indicates that care must be taken when interpreting the results of experiments using TEA to test for monosynaptic connexions.

Further identification of multiple responses mediated by dopamine in the CNS of Planorbis corneus

1978 ◽  
Vol 56 (1) ◽  
pp. 7-18 ◽  
Author(s):  
J. F. MacDonald ◽  
M. S. Berry
Keyword(s):  
Neuroleptic Drugs ◽  
Intracellular Recordings ◽  
Excitatory Postsynaptic Potentials ◽  
Multiple Responses ◽  
Gastropod Mollusc ◽  
Postsynaptic Potentials ◽  
Synaptic Potentials ◽  
Inhibitory Postsynaptic Potentials ◽  
Planorbis Corneus ◽  
Synaptic Responses

Intracellular recordings from neurones, receiving monosynaptic contacts from a dopamine-containing (DA-containing) neurone in the central ganglia of the gastropod mollusc Planorbis corneus, revealed that there are at least three DA-mediated responses. These are 'fast' excitatory postsynaptic potentials (EfPSPs) (200 ms), 'slow' excitatory postsynaptic potentials (EsPSPs) (900 ms), and inhibitory postsynaptic potentials (IPSPs) (200–900 ms). Various combinations of these synaptic potentials were recorded from postsynaptic neurones: EsPSPs, EfPEPs, EsEfPSPs, or EfIPSPs. Neurones receiving such connections also responded appropriately to iontophoresized DA with a 'fast' depolarization (EfPSPs), a 'slow' depolarization (EsPSPs), or a hyperpolarization (IPSPs). These responses could be distinguished on the basis of function (excitation or inhibition), duration, rate of desensitization, and sensitivity to apomorphine, D-LSD, and tubocurarine. The neuroleptic drugs (DA antagonists) haloperidol, fluphenazine, and metoclopramide reduced both excitatory and inhibitory DA transmission. This investigation strongly supports the hypothesis that DA is the transmitter mediating multiple synaptic responses in Planorbis.

Extracellular Magnesium Ion Modifies the Actions of Volatile Anesthetics in Area CA1 of Rat Hippocampus In Vitro 

2002 ◽  
Vol 96 (3) ◽  
pp. 681-687 ◽  
Author(s):  
Rika Sasaki ◽  
Koki Hirota ◽  
Sheldon H. Roth ◽  
Mitsuaki Yamazaki
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Hippocampal Slices ◽  
Volatile Anesthetics ◽  
Population Spike ◽  
Magnesium Ion ◽  
Excitatory Postsynaptic Potential ◽  
Aspartate Receptor ◽  
Postsynaptic Potential

Background Magnesium ion (Mg2+) is involved in important processes as modulation of ion channels, receptors, neurotransmitter release, and cell excitability in the central nervous system. Although extracellular Mg2+ concentration ([Mg2+]o) can be altered during general anesthesia, there has been no evidence for [Mg2+]o-dependent modification of anesthetic actions on neural excitability in central nervous system preparations. The purpose of current study was to determine whether the effects of volatile anesthetics are [Mg2+]o-dependent in mammalian central nervous system. Methods Extracellular electrophysiologic recordings from CA1 neurons in rat hippocampal slices were used to investigate the effects of [Mg2+]o and anesthetics on population spike amplitude and excitatory postsynaptic potential slope. Results The depression of population spike amplitudes and excitatory postsynaptic potential slopes by volatile anesthetics were significantly dependent on [Mg2+]o. The effects were attenuated in the presence of a constant [Mg2+]o/extracellular Ca2+ concentration ratio. However, neither N-methyl-d-aspartate receptor antagonists nor a non-N-methyl-d-aspartate receptor antagonist altered the [Mg2+]o-dependent anesthetic-induced depression of population spikes. Volatile anesthetics produced minimal effects on input-output (excitatory postsynaptic potential-population spike) relations or the threshold for population spike generation. The effects were not modified by changes in [Mg2+]o. In addition, the population spike amplitudes, elicited via antidromic (nonsynaptic) stimulation, were not influenced by [Mg2+]o in the presence of volatile anesthetics. Conclusions These results provide support that alteration of [Mg2+]o modifies the actions of volatile anesthetics on synaptic transmission and that the effects could be, at least in part, a result of presynaptic Ca2+ channel-related mechanisms.

Control of Locomotion in the Freshwater Snail Planorbis Corneus: I. Locomotory Repertoire of the Snail

1990 ◽  
Vol 152 (1) ◽  
pp. 389-404
Author(s):  
T. G. DELIAGINA ◽  
G. N. ORLOVSKY
Keyword(s):  
Nervous System ◽  
Water Surface ◽  
Anterior Part ◽  
Vertical Wall ◽  
Freshwater Snail ◽  
Diurnal Changes ◽  
Vertical Orientation ◽  
Planorbis Corneus ◽  
Food Particles ◽  
Sole Of The Foot

The freshwater snail Planorbis corneas moves as a result of the beating of cilia covering the sole of the foot. The tracks of snails crawling on the walls and on the bottom of an aquarium were recorded visually under various conditions of snail feeding. The following results were obtained. 1. In the absence of food, the snails exhibited diurnal changes in locomotor activity, with a maximum during the day. Horizontal tracks on the aquarium walls were commonest during the day and vertical ones at night. When crawling on the aquarium wall, the snail actively stabilized its horizontal or vertical orientation: when encountering an obstacle or after a forced turn, the snail re-established the initial direction of locomotion. 2. When fed on the water surface, the snail decreased its locomotor speed if food particles entered its mouth. The decrease in speed resulted from the slowing down of ciliary beating in the anterior part of the sole of the foot. This finding demonstrates that motor activity in different parts of the ciliated epithelium can be controlled independently by the nervous system. 3. When searching for food particles, the snail exhibited very sinuous tracks, the turns occurring spontaneously at irregular intervals. This finding shows that there is a programme of ‘looping’ in the nervous system. 4. When the snail was fed on the bottom near a vertical wall, it used the wall to climb to the water surface for lung ventilation. After ventilation, the snail performed a standard 180° turn and then returned to the food along the original outward track. Motion along a track was performed with high accuracy. 5. The locomotor apparatus of a snail allowed it to crawl not only on a flat surface but also along the very thin mucus thread that it makes.

scholarly journals Correlation of Transmitter Release with Membrane Properties of the Presynaptic Fiber of the Squid Giant Synapse

1967 ◽  
Vol 50 (11) ◽  
pp. 2579-2601 ◽  
Author(s):  
Kiyoshi Kusano ◽  
David R. Livengood ◽  
Robert Werman
Keyword(s):  
Transmitter Release ◽  
Time Course ◽  
Membrane Properties ◽  
Ca Current ◽  
Permeability Changes ◽  
Postsynaptic Potential ◽  
Presynaptic Spike ◽  
Squid Giant Synapse ◽  
Giant Synapse ◽  
Tetraethylammonium Ions

Depolarization of the presynaptic terminal by current produced a postsynaptic potential (PSP) which increased with increasing presynaptic polarization and then reached a plateau. Iontophoretic injection of tetraethylammonium ions (TEA) into the presynaptic axon near the terminal produced a prolonged presynaptic spike. The resulting PSP is increased in size and its time course closely followed that of the presynaptic spike. The presynaptic fiber no longer exhibited rectification and strong depolarizations revealed that the PSP reached a maximum with about 110 mv depolarization. Further depolarization produced a decrease in PSP amplitude and finally transmission was blocked. However, a PSP then always appeared on withdrawal of the depolarizing current. Under the conditions of these experiments, the PSP could be considered a direct measure of transmitter release. Bathing the TEA-injected synapse with concentrations of tetrodotoxin (TTX) sufficient to block spike activity in both pre- and postsynaptic axons did not greatly modify postsynaptic electrogenesis. However, doubling TTX concentration reversibly blocked PSP. Thus the permeability changes to Na and K accompanying the spike do not appear necessary for transmitter release. Some other processes related to the level of presynaptic polarization must be involved to explain the data. The inhibition of transmitter release by strong depolarizations appears to be related to Ca action. A membrane Ca current may also be necessary for normal transmitter release.

Properties of neurons of the central nervous system of the freshwater gastropod mollusc

1968 ◽  
Vol 2 (3) ◽  
pp. 743-755
Author(s):  
I. V. Tors'ka ◽  
V. S. Bilokrinits'kyi ◽  
L. F. Burchins'ka ◽  
Ye. D. Genis
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Gastropod Mollusc ◽  
Freshwater Gastropod ◽  
The Central Nervous System
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