Ionic Composition of Haemolymph and Nervous Function in the Cockroach, Periplaneta Americana L

1968 ◽  
Vol 49 (1) ◽  
pp. 31-38
Author(s):  
Y. PICHON ◽  
J. BOISTEL
Keyword(s):  
Action Potentials ◽  
Periplaneta Americana ◽  
Extracellular Fluid ◽  
Sodium Concentration ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Unequal Distribution ◽  
High Sodium ◽  
Giant Axons ◽  
Nerve Cords

1. Resting and action potentials have been recorded in giant axons of the cockroach when the intact nerve cord was bathed in the insect's own haemolymph. 2. Low resting potentials (43.0±4.8 mV.) and large action potentials (105.1±6.8 mV.) were obtained in these preparations as compared with those recorded in de-sheathed nerve cords. 3. Recordings of the maximum rates of rise and fall have shown that the shape of the action potential was essentially similar in de-sheathed preparations and in intact nerve cords. 4. These results have been discussed in terms of the unequal distribution of ions between the haemolymph, the extracellular fluid and the axoplasm of the giant axons. 5. The low measured resting potential agrees with a K+ concentration in the haemolymph of about 20 mM./l., a value which is only slightly lower than the measured one (Pichon, 1963). 6.The occurrence of large action potentials in these apparently depolarized axons may be related to the stabilizing action of divalent cations such as Ca2+ which are contained in the extracellular fluid in relatively large amounts. 7. The very large recorded overshoots (62.1±7.0 mV.) may be linked with a low sodium concentration in the axoplasm and a high sodium concentration in the extracellular fluid of the giant axons of intact nerve cords, thus resulting in a high sodium equilibrium potential, ENa.

Microelectrode Study of the Resting and Action Potentials of the Cockroach Giant Axon with Special Reference to the Role Played by the Nerve Sheath

1967 ◽  
Vol 47 (2) ◽  
pp. 357-373
Author(s):  
Y. PICHON ◽  
J. BOISTEL
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Maximum Rate ◽  
Diffusion Processes ◽  
Extracellular Fluid ◽  
Giant Axon ◽  
Resting Potential ◽  
Giant Axons ◽  
The Mean ◽  
Nerve Cords

1. The use of very fine-tipped and mechanically strong microelectrodes has allowed reliable recordings of resting and action potentials to be made in cockroach giant axons in sheathed and desheathed nerve cords. 2. When the microelectrode was withdrawn from a giant axon in an intact connective the first positive change in the potential from the resting level, was in most cases followed by a negative deflexion to the original zero level, the ‘sheath potential’. The values of this ‘sheath potential’ together with the resting potential, the action potential, the maximum rate of rise and maximum rate of fall of the action potential have been measured in three different salines. 3. In normal saline, resting potentials were lower in sheathed preparations (58·1 ± 55·4 mV.) than in desheathed ones (67·4 ± 6·2 mV.), whereas action potentials were higher in the former (103±5·9 mV.) than in the latter (85·9±4·6 mV.). 4. Elevation of K+ and Ca2+ concentrations in the saline to the haemolymph level resulted in a decrease of resting and action potentials in desheathed cords, to 57·3±5·3 mV. and 36·5±7·6 mV. respectively. No alterations in the membrane potentials were recorded in intact connectives bathed in this saline, the mean resting potential being 55·6±4·2 mV. and the mean action potential 107·9±6·0 mV. Local desheathing of the nerve cord led only to local disturbance of the resting and action potentials, thus indicating that diffusion processes along the extracellular spaces were very slow. 5. The use of a saline in which cation concentrations have been elevated to the extracellular level resulted in normal resting potentials (64·6±3·3 mV.) and action potentials (90·9±7·2 mV.) in desheathed cords, despite the relatively high potassium concentration (17·1 mM./l.). 6. Recordings of the maximum rates of rise and rates of fall showed that there was no significant modification in the shape of the action potential in these different experimental conditions. 7. The values of the ‘sheath potential’ were very variable from one impalement to another and it is suggested that this potential might be related to variations of the microelectrode tip potential bathed in different ionic solutions. 8. The low resting potentials and high action potentials of giant axons in intact nerve cords may result from an excess of inorganic cations in the extracellular fluid.

An electrophysiological analysis of extra-axonal sodium and potassium concentrations in the central nervous system of the cockroach (Periplaneta americana L.)

1975 ◽  
Vol 63 (3) ◽  
pp. 801-811
Author(s):  
M. V. Thomas ◽  
J. E. Treherne
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Action Potentials ◽  
Periplaneta Americana ◽  
Sodium Concentration ◽  
Blood Potassium ◽  
The Central Nervous System ◽  
Sucrose Gap ◽  
Sodium And Potassium

Simultaneous intracellular and sucrose-gap recordings showed, in contrast to previous findings, that the electrical parameters of giant axons were similar to intact and desheathed connectives bathed with the ‘extracellular Ringer’ of Yamasaki & Narahashi. This implies that the extra-axonal sodium concentration, in situ, is likely to be lower than had been previously supposed. Axonal responses showed that, despite the high blood concentration of 24–2 mM-K+ measured by flame photometry, the effective concentration in the blood was 10–15 mM-K+ which corresponds to the measurements made with potassium-selective electrodes. The activity of the blood potassium ions caused a marked reduction in the amplitude of the action potentials following surgical desheathing or disruption of the blood-brain barrier with hypertonic urea. It is suggested that a regulatory mechanism exists in the central nervous system which counteracts the effects of the high blood potassium level.

scholarly journals The Effect of High Sodium Concentration on the Action Potential of the Skate Heart

1967 ◽  
Vol 50 (3) ◽  
pp. 505-517 ◽  
Author(s):  
Issei Seyama ◽  
Hiroshi Irisawa
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Sea Water ◽  
Least Squares Method ◽  
Sodium Concentration ◽  
High Sodium ◽  
Low Sodium ◽  
Other Substances ◽  
Almost All ◽  
High Sodium Concentration

It already has been well documented that the maximum rate of depolarization and amplitude of action potentials are directly dependent on [Na+]o in the vertebrate myocardium. Almost all studies have been carried out at low sodium concentration ranges by substituting NaCl for other substances. Action potentials should be demonstrable in higher sodium concentrations, but cells are inevitably damaged by osmotic changes. The blood of elasmobranchs is nearly isosmotic with sea water, but NaCl accounts for 54.5% of the osmotic pressure and 38.7% of it is maintained by urea molecules. Utilizing this special situation in elasmobranchs, the effect of high sodium concentration was studied up to 170% of normal sodium concentration, while still retaining isosmotic condition. The rate of depolarization, amplitude, and duration of the myocardial action potential all increased in direct proportion to [Na+]o, and no depressant effect on transmembrane action potentials was observed in solutions of high sodium concentration. With regard to depolarization rate, the regression curve fitted by the least squares method passed through zero within two standard errors. At high sodium levels, the overshoot changed as expected theoretically, but at lower ranges it deviated from the theoretical values. [Na+]i, and [K+]i, in this tissue have been determined, and these data are explained on the basis of the Na theory.

Slowly inactivating outward currents in a cuticular mechanoreceptor neuron of the cockroach (Periplaneta americana)

1995 ◽  
Vol 74 (3) ◽  
pp. 1200-1211 ◽  
Author(s):  
P. H. Torkkeli ◽  
A. S. French
Keyword(s):  
Voltage Clamp ◽  
Time Constant ◽  
Action Potentials ◽  
Periplaneta Americana ◽  
Outward Current ◽  
Equilibrium Potential ◽  
Channel Blockers ◽  
Outward Currents ◽  
Frequency Of Action Potentials ◽  
K Outward Current

1. Although rapid adaptation is a widespread feature of sensory receptors, its ionic basis has not been clearly established in any touch receptor, because their small sizes have severely restricted the range of experiments tat can be performed. In the cockroach tactile spine, intracellular voltage-clamp recordings are now possible. 2. The basic electrophysiological properties of the cockroach femoral tactile spine neuron were studied using discontinuous (switching) single-electrode current- and voltage-clamp recordings. A slowly inactivating voltage-sensitive K+ outward current was detected after the major inward currents were blocked with tetrodotoxin. 3. The total outward current activated in < 1 ms at voltages above 0 mV. At moderate depolarizations it did not inactivate, but at higher depolarizations an inactivation time constant of approximately 260 ms was measured. Some recordings also revealed an additional, slower inactivation time constant of approximately 2.5 s. 4. More than half of the voltage-sensitive K+ outward current could be blocked with the Ca2+ channel blockers Co2+ and Cd2+. Tetraethylammonium chloride (TEA) also reduced the amplitude of the outward current to about half of its original amplitude. The actions of both blockers were reversible and probably reflect overlapping blockades of two separate outward currents. 5. The reversal potentials of the currents that remained after block with Co2+ (-91.7 mV) or TEA (-86.8 mV) were both near the K+ equilibrium potential expected for the tactile spine neuron. The voltage dependencies of activation of the Co(2+)- and TEA-resistant currents were both well fitted by Boltzmann distributions, giving values of half maximal activation (V50) equal to -34.5 mV for the Co(2+)-resistant current and -51.3 mV for the TEA-resistant current. 6. Current-clamp recordings revealed that the TEA-sensitive K+ current was the major component of action potential repolarization but that it did not effect the frequency of action potentials evoked by steady depolarization. On the other hand, blockers of Ca(2+)-sensitive K+ currents (Cd2+, Co2+, or charybdotoxin) reduced adaptation and increased the frequency of action potentials significantly but did not effect the duration or amplitude of individual action potentials.

scholarly journals Current Separations in Myxicola Giant Axons

1969 ◽  
Vol 54 (6) ◽  
pp. 741-754 ◽  
Author(s):  
L. Goldman ◽  
L. Binstock
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Reversal Potential ◽  
Transient Current ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Resting Membrane Potential ◽  
Concentration Data ◽  
Giant Axons ◽  
Current Reversal

The effect of reducing the external sodium concentration, [Na]o, on resting potential, action potential, membrane current, and transient current reversal potential in Myxicola giant axons was studied. Tris chloride was used as a substitute for NaCl. Preliminary experiments were carried out to insure that the effect of Tris substitution could be attributed entirely to the reduction in [Na]o. Both choline and tetramethylammonium chloride were found to have additional effects on the membrane. The transient current is carried largely by Na, while the delayed current seems to be independent of [Na]o. Transient current reversal potential behaves much like a pure Nernst equilibrium potential for sodium. Small deviations from this behavior are consistent with the possibility of some small nonsodium component in the transient current. An exact PNa/PK for the transient current channels could not be computed from these data, but is certainly well greater than unity and possibly quite large. The peak of the action potential varied with [Na]o as expected for a sodium action potential with some substantial potassium permeability at the time of peak. Resting membrane potential is independent of [Na]o. This finding is inconsistent with the view that the resting membrane potential is determined only by the distribution of K and Na, and PNa/PK. It is suggested that PNa/PK's obtained from resting membrane potential-potassium concentration data do not always have the physical meaning generally attributed to them.

Recurrent Inhibition in the Giant-Fibre System of the Crayfish and Its Effect on the Excitability of the Escape Response

1968 ◽  
Vol 48 (3) ◽  
pp. 545-567
Author(s):  
ALAN ROBERTS
Keyword(s):  
Escape Response ◽  
Time Course ◽  
Excitatory Input ◽  
Recurrent Inhibition ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Giant Fibre ◽  
Impulse Generation ◽  
Giant Axons ◽  
Slow Potentials

1. A single impulse in any one of the central giant fibres of the crayfish is sufficient to evoke a full escape response. 2. Following such a single impulse a search was made for inhibitory processes of similar duration to the driving movement of the escape response. 3. There is no inhibition of flexor motoneurones or muscles to prevent response to impulses in the central giant axons during the escape response. However, following an impulse in any central giant, intracellular recording showed that there is inhibition of excitatory input to the lateral giants in the abdomen. This inhibition suppresses impulse generation for the duration of the escape response. 4. The inhibition coincides with slow, depolarizing potentials in the lateral giants. These have an equilibrium potential between the normal resting potential and the threshold for spike initiation in the lateral giants. During these slow potentials there is a postsynaptic resistance decrease coinciding very closely in time course with the inhibition of excitatory input. The slow potentials are therefore identified as IPSPs (inhibitory postsynaptic potentials) because of their close association with a postsynaptic inhibitory process. This conclusion is endorsed: (a) by the absence of similar slow potentials in the abdominal medial giants which have no excitatory input at this location, and (b) by the diminution of the slow potentials by picrotoxin, a drug known to block inhibition at many crustacean synapses. 5. When evoked repetitively, even at low frequencies like 0.25 per sec, the IPSPs decrease in amplitude. No other ‘after effects’ of repeated activity were found. 6. Attempts to localize the inhibitory synapses are frustrated by the large space constant of the lateral giants. However, the evidence is compatible with the notion that inhibition originates within each abdominal ganglion. There is occlusion and crossed response decrement between the central giant axons evoking lateral giant inhibition. This suggests that the different presynaptic fibres excite some common inhibitory pathway in each ganglion. Further experiments showed that pathways producing inhibition in one ganglion can be excited in others. Interneuronal arrangements to explain properties of the inhibitory pathways are discussed. 7. Two functions are suggested for the recurrent inhibition in the crayfish lateral giants. First, it may limit the number of impulses that are evoked by a single afferent excitatory volley. Secondly, it may coordinate successive escape responses by suppressing impulse generation in the lateral giants during such responses.

scholarly journals The sodium current underlying action potentials in guinea pig hippocampal CA1 neurons.

1988 ◽  
Vol 91 (3) ◽  
pp. 373-398 ◽  
Author(s):  
P Sah ◽  
A J Gibb ◽  
P W Gage
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Sodium Current ◽  
Hippocampal Slices ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Sodium Currents ◽  
Time To Peak ◽  
Ca1 Region ◽  
Inward Currents

Neurons were acutely dissociated from the CA1 region of hippocampal slices from guinea pigs. Whole-cell recording techniques were used to record and control membrane potential. When the electrode contained KF, the average resting potential was about -40 mV and action potentials in cells at -80 mV (current-clamped) had an amplitude greater than 100 mV. Cells were voltage-clamped at 22-24 degrees C with electrodes containing CsF. Inward currents generated with depolarizing voltage pulses reversed close to the sodium equilibrium potential and could be completely blocked with tetrodotoxin (1 microM). The amplitude of these sodium currents was maximal at about -20 mV and the amplitude of the tail currents was linear with potential, which indicates that the channels were ohmic. The sodium conductance increased with depolarization in a range from -60 to 0 mV with an average half-maximum at about -40 mV. The decay of the currents was not exponential at potentials more positive than -20 mV. The time to peak and half-decay time of the currents varied with potential and temperature. Half of the channels were inactivated at a potential of -75 mV and inactivation was essentially complete at -40 to -30 mV. Recovery from inactivation was not exponential and the rate varied with potential. At lower temperatures, the amplitude of sodium currents decreased, their time course became longer, and half-maximal inactivation shifted to more negative potentials. In a small fraction of cells studied, sodium currents were much more rapid but the voltage dependence of activation and inactivation was very similar.

Mineral Metabolism in Affective Disorders

1965 ◽  
Vol 111 (481) ◽  
pp. 1133-1142 ◽  
Author(s):  
Alec Coppen
Keyword(s):  
Sodium Chloride ◽  
Affective Disorders ◽  
Extracellular Space ◽  
Action Potentials ◽  
Mineral Metabolism ◽  
Extracellular Fluid ◽  
Sodium Concentration ◽  
Intracellular Concentration ◽  
Physiological Research ◽  
Very High

Physiological research has shown the fundamental importance of electrolytes in the functioning of the cell. According to the ionic theory, the resting and action potentials of nerve and muscle cells depend on potassium, sodium, chloride and other ions having a different concentration inside the cell to the concentration they have in the extracellular fluid. The cell membrane is freely permeable to potassium and chloride, but is much less permeable to sodium, and there is active transport of sodium which keeps the sodium concentration within the cell at about 1/10 of the concentration of sodium in the extracellular space. Because of this uneven distribution of sodium and the presence within the cell of impermeable anions (such as glutamic acid), potassium and chlorine are also unevenly divided between the cell and the extracellular fluid; potassium has a very high intracellular concentration and chlorine a low intracellular concentration compared to their concentration in the extracellular space.

scholarly journals Histological and electrophysiological Studies On The Giant Axons Of The Cockroach Periplaneta Americana

1969 ◽  
Vol 50 (3) ◽  
pp. 629-634
Author(s):  
M. E. SPIRA ◽  
I. PARNAS ◽  
F. BERGMANN
Keyword(s):  
Nerve Cord ◽  
Periplaneta Americana ◽  
American Cockroach ◽  
Giant Axons ◽  
Electrophysiological Studies ◽  
Nerve Cords

1. Nerve cords of the American cockroach were cut between the 5th and 6th abdominal ganglia. 2. All giant axons degenerated in the abdominal regions and were present but collapsed in the thoracic connectives. 3. Unilateral lesions permitted identification of ventral giant axons all along the nerve cord.

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