Effects of γ-Aminobutyric Acid and Picrotoxin on the Permeability of the Longitudinal Muscle of the Earthworm to Various Anions

1969 ◽  
Vol 51 (2) ◽  
pp. 363-375
Author(s):  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Membrane Potential ◽  
Response Curve ◽  
Longitudinal Muscle ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Input Resistance ◽  
Ringer Solution ◽  
Aminobutyric Acid ◽  
Inhibitory Junction Potential ◽  
Junction Potential

The effects of GABA and picrotoxin on the input resistance of the muscle of the earthworm, Pheretima communissima in Ringer solution and in solutions containing various foreign anions were observed. 1. Substitution of Cl- by I- and Br- reduced the input resistance and hyperpolarized the membrane. Although anions larger than chloride in hydrated size increased the input resistance, no change of the membrane potential was observed. 2. GABA reduced the input resistance of the membrane and picrotoxin increased it in Ringer solution. The dose-response curve for the changes of the input resistance under various concentrations of GABA shifted parallel-wise under treatment with picrotoxin. 3. In the presence of foreign anions which had larger hydration size than Br-, GABA reduced the input resistance. Picrotoxin did not, however, increase the input resistance when the solutions contained anions of smaller hydration size than ClO4-. 4. Reversal potential levels for the miniature inhibitory junction potential in various concentrations of chloride were measured. The change of the reversal potential levels produced by a tenfold change of chloride concentration was 25 mV.

GABAA-Dependent Chloride Influx Modulates Reversal Potential of GABAB-Mediated IPSPs in Hippocampal Pyramidal Cells

2001 ◽  
Vol 85 (6) ◽  
pp. 2381-2387
Author(s):  
Valeri Lopantsev ◽  
Philip A. Schwartzkroin
Keyword(s):  
Membrane Potential ◽  
Mossy Fiber ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Intracellular Chloride ◽  
The Impact ◽  
Intracellular Chloride Concentration ◽  
Chloride Influx ◽  
Hippocampal Pyramidal Cells

Changes in intracellular chloride concentration, mediated by chloride influx through GABAA receptor–gated channels, may modulate GABAB receptor–mediated inhibitory postsynaptic potentials (GABAB IPSPs) via unknown mechanisms. Recording from CA3 pyramidal cells in hippocampal slices, we investigated the impact of chloride influx during GABAA receptor–mediated IPSPs (GABAA IPSPs) on the properties of GABAB IPSPs. At relatively positive membrane potentials (near −55 mV), mossy fiber–evoked GABAB IPSPs were reduced (compared with their magnitude at −60 mV) when preceded by GABAAreceptor–mediated chloride influx. This effect was not associated with a correlated reduction in membrane permeability during the GABAB IPSP. The mossy fiber–evoked GABAB IPSP showed a positive shift in reversal potential (from −99 to −93 mV) when it was preceded by a GABAA IPSP evoked at cell membrane potential of −55 mV as compared with −60 mV. Similarly, when intracellular chloride concentration was raised via chloride diffusion from an intracellular microelectrode, there was a reduction of the pharmacologically isolated monosynaptic GABABIPSP and a concurrent shift of GABAB IPSP reversal potential from −98 to −90 mV. We conclude that in hippocampal pyramidal cells, in which “resting” membrane potential is near action potential threshold, chloride influx via GABAA IPSPs shifts the reversal potential of subsequent GABAB receptor–mediated postsynaptic responses in a positive direction and reduces their magnitude.

Electrical properties of frog motoneurons in the in situ spinal cord

1976 ◽  
Vol 39 (3) ◽  
pp. 459-473 ◽  
Author(s):  
P. C. Magherini ◽  
W. Precht
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Electrical Properties ◽  
Rana Temporaria ◽  
Reversal Potential ◽  
Input Resistance ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Spike Initiation

Electrical properties of the spinal motoneurons of Rana temporaria and R. esculenta were investigated in the in situ spinal cord at 20-22 degrees C by means of intracellular recording and current injection. Input resistance values depended on the method of measurement in a given cell but were generally inversely related to axon conduction velocity. The membrane-potential response to a subthreshold current pulse was composed of at least two exponentials with mean time constants of 2.5 and 20 ms. The membrance potential reached by the peak of a spike depended on the mode of spike initiation and membrane potential. Preceding a suprathreshold depolarization by a hyperpolarizing pulse could delay and eliminate spike initiation, similar to effects reported in certain invertebrate neurons. Antidromic invasion frequently failed in motoneurons of normal resting potential. Antidromic spike components (m,IS, SD) were similar to those of cat motoneurons. The delayed depolarization and the long afterhyperpolarization following an antidromic spike had many properties in common with the analogous afterpotentials of cat motoneurons. The reversal potential of the short afterhyperpolarization occurring immediately after the spike varied with resting potential and could not be used to determine potassium equilibrium potential. Sustained rhythmic firing could be evoked by continuous synaptic drive or long pulses of injected current. The plot of firing rate versus current strength had a substantial linear region. Both steady firing and adaptation properties varied markedly with motoneuron input resistance.

MODULATION OF TENSION PRODUCTION BY OCTOPAMINE IN THE METATHORACIC DORSAL LONGITUDINAL MUSCLE OF THE CRICKET TELEOGRYLLUS OCEANICUS

1990 ◽  
Vol 149 (1) ◽  
pp. 161-176
Author(s):  
BRUCE A. O'GARA ◽  
CHARLES D. DREWES
Keyword(s):  
Membrane Potential ◽  
Relaxation Rate ◽  
Longitudinal Muscle ◽  
Muscle Relaxation ◽  
Input Resistance ◽  
Muscle Membrane ◽  
Teleogryllus Oceanicus ◽  
Octopamine Receptors ◽  
Metathoracic Ganglion ◽  
Differential Responsiveness

1. Application of octopamine to the metathoracic dorsal longitudinal muscle (DLM) of the cricket Teleogryllus oceanicus produced dose-dependent increases twitch amplitude, contraction rate and relaxation rate. The threshold for octopamine effects was between 10−8 and 10−7moll−1, while maximal effects were seen at approximately 10−5moll−1 2. The octopamine receptors were classified as octopamine2 receptors on the basis of the differential responsiveness of the muscle to the octopamine agonists naphazoline, tolazoline, clonidine and the octopamine antagonists metoclopramide and chlorpromazine. It was not possible to distinguish between octopamine2A or octopamine2B receptors in this preparation. 3. Octopamine had both presynaptic and postsynaptic effects, since it increased both miniature end-plate potential (mEPP) frequency and muscle relaxation rate 4. At a calcium concentration of 11 mmoll−1, octopamine did not affect muscle membrane potential, input resistance or EJP amplitude, but the EJP duration at half amplitude (T½) was slightly increased. In low-calcium saline (1.8 mmol−1), octopamine did not affect membrane potential or T½, but EJP amplitude was increased 5. Stimulation of the octopaminergic dorsal unpaired median neuron (DUMDL), which innervates the metathoracic DLM, increased twitch amplitude about 25% of the preparations. Failure in the other preparations wasapparently due to spike conduction failure within the metathoracic ganglion.6. These results show that octopamine can be an important modulator of metathoracic DLM tension production

Effects of Divalent Cations on Spike Generation in the Longitudinal Somatic Muscle of the Earthworm

1970 ◽  
Vol 52 (1) ◽  
pp. 79-94
Author(s):  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Membrane Potential ◽  
Maximum Rate ◽  
Calcium Concentration ◽  
Divalent Cations ◽  
Input Resistance ◽  
Ringer Solution ◽  
Membrane Potentials ◽  
Free Solution ◽  
Spike Generation ◽  
Maximum Rate Of Rise

Effects of various divalent cations on the spike-generation mechanism in the longitudinal muscle of the earthworm, Pheretima communissima, under sodium-free conditions were observed. 1. In the sodium-free solution the membrane was hyperpolarized from -35 mV. to -55 mV. and the input resistance of the membrane increased from 32 MΩ to 52 MΩ. The spike amplitude was greater in sodium-free solution than in Ringer solution. 2. The amplitude of the spike elicited by intracellular depolarizing currents in sodium-free solution was proportional to the external calcium concentration. The slope of the overshoot potential against tenfold change of the calcium concentration was 26 mV. Similar results could be observed with strontium. 3. The threshold membrane potentials for spike generation varied under various concentrations of calcium. Strontium had nearly the same effect as calcium on the threshold membrane potential. 4. The maximum rates of rise of the spike under various damped membrane potentials were measured in sodium-free solution. The maximum rates of rise of the spike showed sigmoidal curve against the changes of the membrane potential. The half-value of the inactivation curve was estimated to be -32 mV. 5. It was concluded that the spike was elicited by the inward movement of calcium ions, presumably not only in sodium-free solution but also in normal Ringer solution. 6. Strontium and barium ions also carried current during the active state of the membrane. 7. Barium, however, inhibited the potassium conductance of the membrane during the resting and active states, i.e. depolarized the membrane, increased the input resistance of the membrane and prolonged the falling phase of the spike. 8. Magnesium of itself could not elicit the spike in sodium-free solution but prevented spike generation by elevating the threshold membrane potential in the presence of calcium. In the presence of 10 mM Mg, the overshoot potentials recorded in the various concentrations of calcium were not affected, but the maximum rate of rise of the spike was reduced. 9. Cobalt and manganese elevated the threshold membrane potential without changing the resting membrane potential and prevented spike generation. Cobalt was more effective than manganese in preventing spike generations. Cobalt and manganese reduced the amplitude of the overshoot potential and the maximum rate of rise of the spike.

Basolateral ionic permeabilities of macula densa cells

1991 ◽  
Vol 260 (6) ◽  
pp. F856-F860 ◽  
Author(s):  
J. Y. Lapointe ◽  
P. D. Bell ◽  
A. M. Hurst ◽  
J. Cardinal
Keyword(s):  
Membrane Potential ◽  
Basolateral Membrane ◽  
Ringer Solution ◽  
Macula Densa ◽  
Bathing Solution ◽  
Liquid Junction ◽  
Transport Pathways ◽  
Cl Conductance ◽  
Junction Potential ◽  
Basolateral Membrane Potential

It has recently been shown that membrane ionic transport pathways of macula densa cells can be measured using conventional microelectrodes. To determine if conductances could be identified at the basolateral membrane of macula densa cells, cortical thick ascending limbs (CTAL) with attached glomeruli were continuously perfused with a 25 mM NaCl bicarbonate-free Ringer solution. Individual basolateral Na+, Cl-, NaCl, and K+ concentrations were altered by isosmotic replacement with N-methyl-D-glucamine and/or cyclamate. Reduction in basolateral [Na+] from 150 to 25 mM hyperpolarized basolateral membrane potential (Vbl) by 9.9 +/- 1.3 mV (n = 10; all data are corrected for changes in liquid junction potential at bath electrode). A decrease in bath [Cl-] from 150 to 25 mM depolarized Vbl by 20 +/- 2.4 mV (n = 13), whereas decreases in bath [NaCl] from 150 to 25 mM depolarized Vbl by 29 +/- 6.8 mV (n = 5). In the presence of 150 mM NaCl bathing solution, a stepwise increase in [K+] from 5 to 15 mM (by replacement of 10 mM NaCl with 10 mM KCl) depolarized Vbl by 3.3 +/- 1.1 mV (n = 8). After correction for individual transepithelial diffusion potentials, Cl conductance averaged 59 +/- 19% of the total basolateral conductance, whereas K+ (23 +/- 8%) and Na+ (17 +/- 10%) contributed significantly less to the overall basolateral conductance. These results indicate that membrane potential of macula densa cells may be very sensitive to alterations in intracellular Cl- activity and suggest that apical transport of NaCl through a furosemide-sensitive Na(+)-K(+)-2Cl- transporter may affect membrane potential in macula densa cells via a change in intracellular Cl- activity.

Rat hippocampal astrocytes exhibit electrogenic sodium-bicarbonate co-transport

1994 ◽  
Vol 72 (6) ◽  
pp. 2580-2589 ◽  
Author(s):  
E. R. O'Connor ◽  
H. Sontheimer ◽  
B. R. Ransom
Keyword(s):  
Membrane Potential ◽  
Reversal Potential ◽  
Input Resistance ◽  
Membrane Potentials ◽  
Resting Membrane Potential ◽  
Induced Response ◽  
Potential Range ◽  
Free Solution ◽  
Hippocampal Astrocytes ◽  
In Cells

1. We probed for the expression of electrogenic Na+/HCO3- co-transport in cultured mammalian astrocytes by recording voltage and current changes induced by bath application of HCO3-, with the use of patch-clamp electrophysiology. Application of 25 mM HCO3-, at a constant pHo, to astrocytes bathed in a nominally HCO3(-)-free solution, produced an abrupt and reversible change in membrane potential ranging from +3 to -30 mV [-11.8 +/- 9.34 (SD) mV]; 55% of cells showed relatively large hyperpolarizing responses (-18.8 +/- 6.23 mV), whereas 45% showed only small shifts in membrane potential (range of -5 to +3 mV; -1.9 +/- 1.96 mV). 2. The size of the HCO3(-)-induced hyperpolarization was strongly related to the cell's initial resting membrane potential in HCO3(-)-free solution; the larger responses were seen in cells with relatively low resting membrane potentials (-48.5 +/- 9.4 mV), and the smaller responses were seen in cells with more negative potentials (-68.1 +/- 6.5 mV). The membrane potentials of hippocampal astrocytes were highly variable in HCO3(-)-free solution (range -38 to -80 mV; -60.9 +/- 12.53); this variability was greatly reduced in HCO3(-)-containing solution (range -59 to -82 mV; -68.5 +/- 4.8). 3. The magnitude of the HCO3(-)-induced response was less strongly correlated with cell input resistance, which was higher in the larger responder cells than in the small responders. However, the differences in input resistance were insufficient to account for the different HCO3(-)-induced responses observed. 4. In the presence of extracellular Ba2+, which by blocking K+ conductance depolarized cells by 30-50 mV, cells that initially showed a small response, showed a large and completely reversible hyperpolarization (-18.4 +/- 6.13 mV) to application of 25 mM HCO3-. In Na(+)-free solution, the HCO3(-)-induced hyperpolarization was reduced by 66%, and the response was not sustained, as in Na(+)-containing solution. Removal of extracellular Cl- had no effect on the HCO3- response The stilbene derivative 4,4'-diisothiocyano-2,2'-stilbene disulfonate (DIDS), a blocker of anion transport, eliminated the HCO3(-)-induced hyperpolarization. Blockers of Na+/K+ ATPase and Na(+)-H+ exchange were without effect. These observations indicated the presence of an electrogenic Na+/HCO3- co-transporter in hippocampal astrocytes. 6. Voltage-clamp recording demonstrated that the HCO3(-)-induced hyperpolarization was caused by outward currents averaging 335 +/- 104 pA. The reversal potential of the HCO3(-)-induced current ranged between -80 and -99 mV with an average = -86.1 +/- 6.2 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Noncholinergic membrane potential responses to transmural nerve stimulation in the guinea pig ileum

1991 ◽  
Vol 260 (2) ◽  
pp. G240-G249
Author(s):  
J. R. Crist ◽  
X. D. He
Keyword(s):  
Membrane Potential ◽  
Nerve Stimulation ◽  
Circular Muscle ◽  
Longitudinal Axis ◽  
Muscle Layer ◽  
Abrupt Onset ◽  
Neural Pathways ◽  
Neural Input ◽  
Inhibitory Junction Potential ◽  
Junction Potential

We sought to characterize the projections of nonmuscarinic intramural inhibitory and excitatory neural input to the circular muscle layer of the small intestine. Intracellular membrane potential recordings were made in smooth muscle cells from the distal ileum of 22 guinea pigs. Intramural nerve stimulation (4 pulses, 15 mA, 20 Hz, 2 ms) was delivered by two electrodes located at varying distances from the recording electrode along the longitudinal axis of the intestine. The membrane potential responses immediately oral to the stimulus consisted of an abrupt-onset inhibitory junction potential (IJP) followed by two distinct depolarizations, an early excitatory junction potential (EJP) and a late EJP. The early IJP and early and late EJPs were observed as far as 53 +/- 5, 56 +/- 6, and 39 +/- 5 mm oral to the stimulus, respectively. The responses immediately anal to the stimulus consisted of an initial IJP followed by a prolonged hyperpolarization, which was sometimes interrupted by a superimposed EJP. The early IJP, EJP, and late IJP were observed as far as 77 +/- 12, 66 +/- 10, and 37 +/- 13 mm anal to the stimulus, respectively. All excitatory events greater than 5-10 mm oral or anal to the stimulus were blocked by hexamethonium. Hexamethonium slightly antagonized the early IJP oral to the stimulus but had no effect on the early IJP anal to the stimulus. The late IJP was not affected by hexamethonium. These studies are the first to describe a late IJP, which is observed only at sites anal to the stimulus, and a late EJP, which is observed only at sites oral to the stimulus. The neural pathways involved in these late synaptic events (late EJP and IJP) as well as the previously described early synaptic events (early EJP and IJP) are discussed.

In vitro electrophysiology of developing genioglossal motoneurons in the rat

1993 ◽  
Vol 70 (4) ◽  
pp. 1401-1411 ◽  
Author(s):  
P. A. Nunez-Abades ◽  
J. M. Spielmann ◽  
G. Barrionuevo ◽  
W. E. Cameron
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Reversal Potential ◽  
Input Resistance ◽  
Membrane Properties ◽  
Inward Rectification ◽  
Postnatal Change ◽  
The Mean ◽  
Made In

1. Experiments were performed to determine the change in membrane properties of genioglossal (GG) motoneurons during development. Intracellular recordings were made in 127 GG motoneurons from rats postnatal ages 1-30 days. 2. The input resistance (R(in)) and the membrane time constant (t(aum)) decreased between 5-6 and 13-15 days from 84.8 +/- 25.4 (SD) to 47.0 +/- 18.9 M omega (P < 0.01) and from 10.0 +/- 4.2 to 7.3 +/- 3.3 ms (P < 0.05), respectively. During this period, the rheobase (Irh) increased (P < 0.01) from 0.13 +/- 0.07 to 0.27 +/- 0.14 nA, and the percentage of cells exhibiting inward rectification increased from 5 to 40%. Voltage threshold (Vthr) of the action potential remained unchanged postnatally. 3. There was also a postnatal change in the shape of the action potential. Specifically, between 1-2 and 5-6 days, there was a decrease (P < 0.05) in the spike half-width from 2.23 +/- 0.53 to 1.45 +/- 0.44 ms, resulting, in part, from a steepening (P < 0.05) of the slope of the falling phase of the action potential from 21.6 +/- 10.1 to 32.9 +/- 13.1 mV/ms. The slope of the rising phase also increased significantly (P < 0.01) between 1-2 and 13-15 days from 68.4 +/- 31.0 to 91.4 +/- 44.3 mV/ms. 4. The average duration of the medium afterhyperpolarization (mAHPdur) decreased (P < 0.05) between 1-2 (193 +/- 53 ms) and 5-6 days (159 +/- 43 ms). Whereas the mAHPdur was found to be independent of membrane potential, there was a linear relationship between the membrane potential and the amplitude of the medium AHP (mAHPamp). From this latter relationship, a reversal potential for the mAHPamp was extrapolated to be -87 mV. No evidence for the existence of a slow AHP was found in these developing motoneurons. 5. All cells analyzed (n = 74) displayed adaptation during the first three spikes. The subsequent firing pattern was classified into two groups, adapting and nonadapting. Cells at birth were all adapting, whereas all cells but two from animals 13 days and older were nonadapting. At the intermediate age (5-6 days), the minority (27%) was adapting and the majority (73%) was nonadapting. 6. The mean slope of primary range for the first interspike interval (1st ISI) was approximately 90 Hz/nA. This value was similar for both adapting and nonadapting cells and did not change postnatally.(ABSTRACT TRUNCATED AT 400 WORDS)

Can nonadrenergic inhibitory varicosities be Identified structurally

1977 ◽  
Vol 55 (2) ◽  
pp. 243-250 ◽  
Author(s):  
E. E. Daniel ◽  
G. S. Taylor ◽  
V. P. Daniel ◽  
M. E. Holman
Keyword(s):  
Small Proportion ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Muscle Layer ◽  
Intrinsic Nerves ◽  
Inhibitory Junction Potential ◽  
Rabbit Jejunum ◽  
Junction Potential ◽  
Stimulation Of

The distribution of vesicles in axon varicosities was examined in rabbit jejunum and opossum esophagus. Circular muscle cells of both rabbit jejunum and opossum esophagus responded to stimulation of intrinsic nerves with inhibitory junction potential in nearly all cases. Inhibitory junction potentials were rare and small in longitudinal muscle cells of rabbit jejunum. There were few axon varicosities with a predominance of large opaque vesicles or large dense-cored vesicles in any muscle layer of rabbit or opossum or in the plexuses of rabbit jejunum. There were almost as high a proportion of such varicosities in longitudinal as in circular muscle of rabbit jejunum, and there were almost none in circular muscle of opossum esophagus. The distribution of vesicles in varicosities was found often to be heterogeneous and could account for the observed occurrence of a small proportion of varicosities with a predominance of large vesicles. It is suggested that there is no structural distinction in vertebrates between axons which are cholinergic and axons which are nonadrenergic inhibitory.

Neuromuscular Transmission in the Longitudinal Layer of Somatic Muscle in the Earthworm

1969 ◽  
Vol 50 (2) ◽  
pp. 417-430
Author(s):  
T. HIDAKA ◽  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Equilibrium Potential ◽  
Muscle Fibres ◽  
Free Solution ◽  
Excitatory Junction Potentials ◽  
Potential Level

1. The properties of the miniature inhibitory junction potentials (M.I.J.P.) and the inhibitory junction potentials (I.J.P.) elicited by nerve stimulation were investigated in longitudinal muscle fibres of the earthworm. 2. Histograms of the amplitudes(mean,0.71mV.) and the intervals (mean, 101 msec.) of the M.I.J.P. showed skew curves. 3. The polarity of the M.I.J.P. was reversed at about -60 mV. When the external chloride was substituted by glutamate the M.I.J.P. disappeared as an external chloride concentration of 15-20 mM, and further reduction reversed their polarity. 4. Picrotoxin blocked generation of the M.I.J.P. and the I.J.P. 5. The cross-over point of the current-voltage relation curves, with and without presence of GABA, occurred at a membrane potential of -54 mV. in potassium-free solution, and at -56 mV. in potassium-excess solution. 6. Iontophoretic application of GABA produced slow hyperpolarization. The equilibrium potential of the GABA-potential was about -60 mV. During the time course of the GABA-potentials an increase in the membrane conductance was observed. 7. Miniature excitatory junction potentials (M.E.J.P.) and excitatory junction potentials (E.J.P.) could be recorded from the longitudinal muscle, but the M.E.J.P. were rare. 8. D-tubocurarine, but not atropine, completely blocked the M.E.J.P. and E.J.P. Prostigmine enhanced their amplitude and duration. 9. The reversal potential level for the E.J.P. was about 0 mV. Sodium-free solution lowered the reversal potential level for the M.E.J.P. to -20 mV.

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