scholarly journals A Quantitative Study of Potassium Movements in the Central Nervous System of Periplaneta Americana

1970 ◽  
Vol 53 (1) ◽  
pp. 109-136
Author(s):  
J. E. TREHERNE ◽  
N. J. LANE ◽  
R. B. MORETON ◽  
Y. PICHON
Keyword(s):  
Periplaneta Americana ◽  
Electrical Response ◽  
Ionic Composition ◽  
Inorganic Ions ◽  
Potassium Ions ◽  
Bathing Medium ◽  
Outward Diffusion ◽  
Giant Axons ◽  
Intercellular Clefts ◽  
The Central Nervous System

1. Using the electrical response of giant axons in the isolated abdominal nerve cord of the cockroach, Periplaneta americana, as an indication of the ionic composition of the fluid bathing their surfaces, it has been shown that the movement of potassium ions from the bathing medium to the extra-axonal fluid, following an increase in the external concentration of this cation, involves an appreciable degree of restriction. 2. This effect is associated with an extracellular diffusion potential, which appears to result from the more rapid penetration of potassium relative to the outward diffusion of sodium ions from the extracellular system. 3. It is suggested that the restriction of intercellular diffusion may occur in the region containing tight junctions and separate desmosomes at the inner end of the intercellular clefts which traverse the perineurium. 4. If the connectives are stretched during mounting, a more rapid depolarization of the giant axons is observed. Comparison of the calculated and the experimentally observed half-times for diffusion of potassium ions to the axon surface indicates that in these preparations the rate of movement of inorganic ions from the external medium is largely determined by the extended intercellular diffusion pathway represented by the mesaxon cleft. 5. In de-sheathed preparations penetration of potassium ions is still more rapid, an effect which is postulated to result from damage to the perineurium, and the consequent production of a shorter, intracellular diffusion channel through the glial system.

Sodium and Potassium Fluxes in the Abdominal Nerve Cord of the Cockroach, Periplaneta Americana L

1961 ◽  
Vol 38 (2) ◽  
pp. 315-322
Author(s):  
J. E. TREHERNE
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Unit Area ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Nerve Sheath ◽  
The Central Nervous System ◽  
Sodium And Potassium

1. The influx of sodium and potassium ions into the central nervous system of Periplaneta americana has been studied by measuring the increase in radioactivity within the abdominal nerve cord following the injection of 24NA and 42K. into the haemolymph. 2. The calculated influx of sodium ions was approximately 320 mM./l. of nerve cord water/hr. and of potassium ions was 312 mM./l. of nerve cord water/hr. These values are very approximately equivalent to an influx per unit area of nerve cord surface of 13.9 x 10-2 M cm. -2 sec.-1 for sodium and 13.5 x 10-12 M cm. -2 sec.-1 for potassium ions. 3. The relatively rapid influxes of these ions are discussed in relation to the postulated function of the nerve sheath as a diffusion barrier. It is suggested that a dynamic steady state rather than a static impermeability must exist across the sheath surrounding the central nervous system in this insect.

Potassium Movements in a Central Nervous Ganglion of Limnaea Stagnalis (L.) (Gastropoda:Pulmonata)

1973 ◽  
Vol 58 (1) ◽  
pp. 15-28
Author(s):  
D. B. SATTELLE
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Ionic Composition ◽  
Neuronal Membrane ◽  
Potassium Ions ◽  
Bathing Medium ◽  
Limnaea Stagnalis ◽  
The Right ◽  
Surface Changes

1. Resting potentials and action potentials recorded from in situ, intact and desheathed giant neurones of the right parietal ganglion of Limnaea stagnalis are of similar magnitude. Ganglionic potential profiles reveal the absence of a sheath potential. It is concluded that the extra-neuronal fluid has a similar ionic composition to the blood (bathing medium). 2. A 34 mV decade potassium slope is obtained for both intact and de-sheathed neurones. Depolarization of the neuronal membrane takes place rapidly in intact preparations, and the de-sheathing procedure significantly increases the rate of depolarization. 3. A reduction in temperature from 23 to 8°C only slightly prolongs the time-course of depolarization of an intact neurone. When the concentration of potassium in the fluid bathing the surface of an intact ganglion is elevated, the concentration of this cation at the neuronal surface changes exponentially with time. It is suggested therefore that diffusion along the extracellular channels is the mechanism and pathway for the movement of potassium ions through the right parietal ganglion of Limnaea stagnalis.

A Quantitative Study of the Ionic Basis of Extraneuronal Potential Changes in the Central Nervous System of the Cockroach (Periplaneta Americana L.)

1971 ◽  
Vol 54 (3) ◽  
pp. 757-777
Author(s):  
Y. PICHON ◽  
R B. MORETON ◽  
J. E. TREHERNE
Keyword(s):  
Periplaneta Americana ◽  
Narrow Channel ◽  
Sodium Ions ◽  
Nernst Equation ◽  
In Series ◽  
Intercellular Clefts ◽  
The Central Nervous System ◽  
Solution Bathing ◽  
Ionic Basis ◽  
Perineurial Cells

1. Measurements have been made of the extraneuronal potential changes produced by replacement of sodium ions with other organic and inorganic cations in the solution bathing isolated abdominal connectives. 2. On the basis of the observed extraneuronal potential changes it is possible to arrange monovalent cations in the following sequence of effectiveness: K+ > Rb+ > Cs+ > TEA+ > Na+ > Li+ > choline+ > tris+. 3. It is concluded that the ionic dependence of the extraneuronal potentials is similar to that of a theoretical model system consisting of a perineurial diffusion barrier in series with a long, narrow channel representing the system of intercellular clefts connecting the inwardly facing surface of the perineurium with the extraaxonal fluid. 4. On the basis of this model the effect of high external concentrations of, for example, potassium ions would be to depolarize the outwardly facing perineurial cell membranes. The considerable departure of the observed potentials from the values predicted by the Nernst equation can be accounted for in terms of the short-circuiting effect, due to the finite ionic permeability of the tight junctions between perineurial cells. Qualitative predictions can also be made concerning the rates of movement of potassium and sodium ions in the extracellular system.

Axonal Function and Ionic Regulation in the Central Nervous System of a Phytophagous Insect (Carausius Morosus)

1967 ◽  
Vol 47 (2) ◽  
pp. 235-247
Author(s):  
J. E. TREHERNE ◽  
S. H. P. MADDRELL
Keyword(s):  
Ionic Composition ◽  
Extracellular Fluid ◽  
Extracellular Recording ◽  
Inorganic Ions ◽  
Sodium Ions ◽  
Phytophagous Insect ◽  
High Concentration ◽  
Action Current ◽  
Local Regulation ◽  
The Central Nervous System

1. Experiments vising intracellular and extracellular recording techniques indicate that, despite the specialized ionic composition of the haemolymph, the axons in the nerve cord of Carausius are conventional in that the action current is largely carried by sodium ions. 2. This effect is achieved by an appreciable regulation of the concentrations of inorganic ions in the extracellular fluid bathing the axon surfaces. 3. The extra-axonal regulation does not appear to result from any significant restriction in the accessibility of cations to the general extracellular system, but from a local regulation which appears to maintain a relatively high concentration of sodium ions at the axon surfaces. 4. It is suggested that such a regulation may be achieved by an extrusion of sodium ions from the glial cells into the restricted extra-axonal spaces demonstrated in the electron micrographs of this preparation.

Some Effects of the Ionic Composition of the Extracellular Fluid on the Electrical Activity of the Cockroach Abdominal Nerve Cord

1962 ◽  
Vol 39 (4) ◽  
pp. 631-641
Author(s):  
J. E. TREHERNE
Keyword(s):  
Nerve Cord ◽  
Periplaneta Americana ◽  
Ionic Composition ◽  
Conduction Block ◽  
Extracellular Fluid ◽  
Potassium Ions ◽  
Rapid Loss ◽  
Potassium Depolarization ◽  
High Potassium ◽  
Nerve Sheath

1. Irrigation of abdominal ganglia of Periplaneta Americana with salines containing excess potassium ions resulted in the development of a reversible conduction block. Removal of portions of the cellular and fibrous nerve sheath produced an accelerated potassium depolarization as described by Twarog & Roeder (1956). 2. Elevation of the cation concentrations to correspond to the extracellular levels resulted in delayed conduction block in desheathed preparations irrigated with highpotassium saline. At 70 mM./l. K the rate of depolarization was delayed to approximately half that of intact ganglia. At extremely high potassium concentrations this effect became relatively small. 3. It is suggested that the enhanced rates of potassium depolarization obtained in desheathed preparations partly result from the changed ionic composition of the extracellular fluid resulting from the desheathing procedure. The possible additional factors involved in the desheathing procedure are discussed. 4. 50 mM./l. acetylcholine had little effect on the synaptic transmission in intact terminal abdominal ganglia but caused rapid loss of conduction in desheathed preparations. Injection of equivalent amounts of acetylcholine beneath the nerve sheath did not cause rapid conduction block, and it is suggested that the effects of desheathing are not necessarily caused by the removal of a relatively impermeable superficial diffusion barrier.

Responses to Hypersaline Exposure in the Euryhaline Crayfish PAcifastacus Leniusculus: II. Modulation of Haemocyanin Oxygen Binding In Vitro and In Vivo

1982 ◽  
Vol 99 (1) ◽  
pp. 447-467
Author(s):  
MICHÈLE G. WHEATLY ◽  
B. R. MCMAHON
Keyword(s):  
Salt Effect ◽  
Ionic Composition ◽  
Inorganic Ions ◽  
Pacifastacus Leniusculus ◽  
Oxygen Binding ◽  
Complete Saturation ◽  
O2 Delivery ◽  
O2 Binding

The effect of 48 h of hypersaline exposure (25, 50 and 75% SW) on haemocyanin oxygenation properties in the euryhaline crayfish Pacifastacus leniusculus was investigated in vitro and in vivo. In vitro significant increases in affinity and cooperativity were measured, although the magnitude of the Bohr shift was unaffected. In vitro dialysis of haemolymph against physiological salines of variable ionic composition proved that these changes were only partly attributable to altered levels of haemolymph ions, implicating the existence of modulators other than H+ and inorganic ions, the possible identities of which are discussed. Significant depressions of both pre- and postbranchial oxygen tensions (Pv, Ov, O2 and Pa, Oa, O2) were observed, but O2 delivery was maintained by utilization of the venous reserve and by an increase in haemocyanin O2 affinity. This occurred despite a concomitant acidosis whose effect on O2 affinity was directly opposed by the ‘salt’ effect. Under hypersaline conditions, haemocyanin played an increasingly important role in O2 delivery in vivo. Despite a reduction in the concentration of combined O2 at complete saturation of the pigment (CmaxHCyOHCyO2). indicating lowered haemocyanin concentration, compensatory changes in O2-binding and cardiac output precluded an impairment to O2 transfer. Equilibration at the tissues (Et,Ot,O2) in FW was less effective than at the gills (Eb,Ob,O2 but progressively improved with hypersaline exposure reversing this trend. Although effects of increased salinity on O2 equilibrium characteristics were qualitatively similar in vivo and in vitro, some interesting quantitative differences are discussed.

Accessibility of the Central Nervous Connectives of Anodonta Cygnea to a Compound of Large Molecular Weight

1972 ◽  
Vol 56 (2) ◽  
pp. 493-499
Author(s):  
N. J. LANE ◽  
J. E. TREHERNE
Keyword(s):  
Cell Layer ◽  
Extracellular Fluid ◽  
Water Soluble ◽  
Bathing Medium ◽  
Anodonta Cygnea ◽  
Rapid Exchange ◽  
Soluble Ions ◽  
Large Molecular Weight ◽  
Water Soluble Ions ◽  
Intercellular Clefts

1. Ultrastructural observations on the uptake of an exogenous tracer substance, horseradish peroxidase (M.W. 40,000), have shown that this large molecule can penetrate the neural lamella in intact cerebro-visceral connectives of the lamellibranch, Anodonta cygnea. 2. Peroxidase molecules were also observed to penetrate between the intercellular clefts formed by adjacent membranes of the underlying peripheral glial cell layer and to move extensively into the underlying extracellular spaces. 3. These observations confirm the results of previous electrophysiological, radioisotopic and ultrastructural investigations indicating that a relatively rapid exchange of water-soluble ions and molecules occurs between the blood, or bathing medium, and the extracellular fluid bathing the axon surfaces in intact connectives.

Organization of the Giant Axons of the Cockroach Periplaneta Americana

1969 ◽  
Vol 50 (3) ◽  
pp. 615-627
Author(s):  
M. E. SPIRA ◽  
I. PARNAS ◽  
F. BERGMANN
Keyword(s):  
Nerve Cord ◽  
Periplaneta Americana ◽  
Thoracic Ganglion ◽  
American Cockroach ◽  
Abdominal Ganglion ◽  
Common Pathway ◽  
Average Delay ◽  
Giant Axons ◽  
Stimulation Of

1. Stimulation of the connectives between the suboesophageal and prothoracic ganglia of the American cockroach induced ipsilateral descending spikes in the abdominal giant axons with an average delay of 0·6 msec, per thoracic ganglion. 2. Nicotine at 5 µg./ml. had no effect on conduction in the abdomen but blocked ascending responses sequentially at the 6th abdominal ganglion then at the levels of T1; T2, and T3. 3. Simultaneous descending and ascending impulses resulted in mutual extinction along the nerve cord with the point of collision depending on the interval between stimuli. 4. It is suggested that a common pathway subserves ascending and descending giant impulses and models for bi-directional conduction are discussed.

Sign in / Sign up

Export Citation Format

Share Document