Bicuculline, benzyl penicillin, and inhibitory amino acids in the spinal cord of the cat

1977 ◽  
Vol 55 (3) ◽  
pp. 670-680 ◽  
Author(s):  
K. Krnjević ◽  
E. Puil ◽  
R. Werman
Keyword(s):  
Spinal Cord ◽  
Input Resistance ◽  
Aminobutyric Acid ◽  
Membrane Properties ◽  
Gaba Uptake ◽  
Spinal Motoneurons ◽  
Benzyl Penicillin ◽  
Equal Chance ◽  
Conductance Increase ◽  
Inhibitory Amino Acids

Bicuculline methochloride (BMC), applied by microiontophoresis, tends to depolarize spinal motoneurons and lower their input resistance. With approximately equal iontophoretic currents of γ-aminobutyric acid (GABA) and BMC, there is an almost equal chance of observing no change, a potentiation, or a depression of the GABA-evoked conductance increase. A block of the GABA action is seen consistently only when the iontophoretic current of BMC is at least double that of GABA. Under these conditions BMC can selectively antagonize GABA without blocking the effects of glycine, though the latter can also be blocked by larger amounts of BMC. BMC also regularly eliminates the usual apparent desensitization to GABA. This may be due to depression of GABA uptake by BMC, which would also account for its potentiating action at lower relative doses. Comparable effects are observed with iontophoretic applications of benzyl penicillin (BP); but even large doses of BP produce no definite change in membrane properties or in conductance increase evoked by GABA or glycine.

Intraneuronal effects of inhibitory amino acids

1980 ◽  
Vol 58 (2) ◽  
pp. 193-204 ◽  
Author(s):  
A. Constanti ◽  
K. Krnjević ◽  
A. Nistri
Keyword(s):  
Amino Acids ◽  
Transport Mechanism ◽  
Input Resistance ◽  
Aminobutyric Acid ◽  
Spinal Motoneurons ◽  
Gaba Transport ◽  
Aminoisobutyric Acid ◽  
Intracellular Release ◽  
Comparable Effect ◽  
Inhibitory Amino Acids

Injections of γ-aminobutyric acid (GABA) into spinal motoneurons (in cats under Dial) induce a small but relatively prolonged hyperpolarization (mean −1.7 mV, SD 2. 1; n = 25), which is associated with a rise in input resistance (mean 44%, SD 122; n = 34), is not reversed by hyperpolarization, and is not potentiated by intracellular release of benzodiazepines. Muscimol sometimes has a comparable effect, but α-aminoisobutyric acid and glycine do not. These observations are consistent with the possibility that motoneurons have a Na+-coupled GABA transport mechanism that is electrogenic and can be reversed by an excess of intracellular GABA.

Effects of glycine and GABA on bulbar respiratory neurons of cat

1990 ◽  
Vol 63 (5) ◽  
pp. 955-965 ◽  
Author(s):  
A. Haji ◽  
J. E. Remmers ◽  
C. Connelly ◽  
R. Takeda
Keyword(s):  
Membrane Potential ◽  
Amino Acid ◽  
Input Resistance ◽  
Postsynaptic Membrane ◽  
Chloride Ions ◽  
Membrane Receptors ◽  
Membrane Properties ◽  
Respiratory Neurons ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid

1. Bulbar respiratory neurons of unanesthetized, decerebrate cats were impaled with the center pipette of a compound, coaxial microelectrode. This electrode allowed intracellular recording of membrane potential (MP) through the central pipette and extracellular iontophoresis of glycine or gamma-aminobutyric acid (GABA) from micropipettes encircling the center pipette with their tips recessed 20-40 microns from the tip of the center pipette. 2. Seventy-seven studies were carried out on 32 inspiratory and 28 postinspiratory neurons with the use of brief pulses (0.3-0.5 s) or long pulses (3-10 s) spanning one or more respiratory cycles. In both neuronal types, GABA and glycine decreased spike frequency, synaptic "noise," respiratory fluctuations of MP, and "input" resistance in a dose-related fashion. 3. In most cases, the membrane was hyperpolarized by the amino acid. The reverse response (depolarization) was observed when the membrane had been hyperpolarized by current clamp. This reversal from hyperpolarization to depolarization occurred at a MP of -81 +/- 2.3 mV (mean +/- SE, n = 7) for glycine and -81 +/- 1.6 (n = 6) for GABA. 4. After intracellular iontophoresis of chloride ions, application of GABA and glycine depolarized the membrane. 5. During relatively long (3-10 s) periods of iontophoresis of glycine or GABA, the effects on MP and input resistance waned. In some cases (23%), the amino acid depolarized the membrane at the most hyperpolarizated portion of the MP trajectory. This was never observed with brief iontophoretic pulses. Such effects of long duration iontophoresis may reflect changes in membrane properties secondary to the primary action of the amino acid on the membrane of the impaled neuron or indirect synaptic actions via changes in discharge of neighboring neurons. 6. Extracellular iontophoresis of a GABA uptake inhibitor, nipecotic acid, potentiated the effects of GABA. 7. Extracellular application of tetrodotoxin appeared to act pre- and postsynaptically to reduce respiratory fluctuations in membrane potential and to increase input resistance without altering the effects of iontophoresed glycine and GABA, suggesting that the amino acids act on postsynaptic membrane receptors not linked to fast sodium channels.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals An In Vitro Protocol for Recording From Spinal Motoneurons of Adult Rats

2008 ◽  
Vol 100 (1) ◽  
pp. 474-481 ◽  
Author(s):  
Jonathan S. Carp ◽  
Ann M. Tennissen ◽  
Donna L. Mongeluzi ◽  
Christopher J. Dudek ◽  
Xiang Yang Chen ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Action Potential ◽  
Mechanical Stability ◽  
Pharmacological Study ◽  
Input Resistance ◽  
Spinal Motoneurons ◽  
Adult Rats ◽  
Precise Control

In vitro slice preparations of CNS tissue are invaluable for studying neuronal function. However, up to now, slice protocols for adult mammal spinal motoneurons—the final common pathway for motor behaviors—have been available for only limited portions of the spinal cord. In most cases, these preparations have not been productive due to the poor viability of motoneurons in vitro. This report describes and validates a new slice protocol that for the first time provides reliable intracellular recordings from lumbar motoneurons of adult rats. The key features of this protocol are: preexposure to 100% oxygen; laminectomy prior to perfusion; anesthesia with ketamine/xylazine; embedding the spinal cord in agar prior to slicing; and, most important, brief incubation of spinal cord slices in a 30% solution of polyethylene glycol to promote resealing of the many motoneuron dendrites cut during sectioning. Together, these new features produce successful recordings in 76% of the experiments and an average action potential amplitude of 76 mV. Motoneuron properties measured in this new slice preparation (i.e., voltage and current thresholds for action potential initiation, input resistance, afterhyperpolarization size and duration, and onset and offset firing rates during current ramps) are comparable to those recorded in vivo. Given the mechanical stability and precise control over the extracellular environment afforded by an in vitro preparation, this new protocol can greatly facilitate electrophysiological and pharmacological study of these uniquely important neurons and other delicate neuronal populations in adult mammals.

Changes in Electrophysiological Properties of Lamprey Spinal Motoneurons During Fictive Swimming

2002 ◽  
Vol 88 (5) ◽  
pp. 2463-2476 ◽  
Author(s):  
Michelle M. Martin
Keyword(s):  
Spinal Cord ◽  
Input Resistance ◽  
Spike Frequency ◽  
Calcium Currents ◽  
Quiescent State ◽  
Spike Frequency Adaptation ◽  
Free Solution ◽  
Spinal Motoneurons ◽  
Electrophysiological Properties ◽  
Frequency Adaptation

Electrophysiological properties of lamprey spinal motoneurons were measured to determine whether their cellular properties change as the spinal cord goes from a quiescent state to the active state of fictive swimming. Intracellular microelectrode recordings of membrane potential were made from motoneurons in the isolated spinal cord preparation. Electrophysiological properties were first characterized in the quiescent spinal cord, and then fictive swimming was induced by perfusion with d-glutamate and the measurements were repeated. During the depolarizing excitatory phase of fictive swimming, the motoneurons had significantly reduced rheobase and significantly increased input resistance compared with the quiescent state, with no significant changes in these parameters during the repolarizing inhibitory phase of swimming. Spike threshold did not change significantly during fictive swimming compared with the quiescent state. During fictive swimming, the slope of the spike frequency versus injected current ( F-I) relationship decreased significantly as did spike-frequency adaptation and the amplitude of the slow after-spike hyperpolarization (sAHP). Serotonin is known to be released endogenously from the spinal cord during fictive swimming and is known to reduce the amplitude of the sAHP. Therefore the effects of serotonin on cellular properties were tested in the quiescent spinal cord. It was found that, in addition to reducing the sAHP amplitude, serotonin also reduced the slope of the F-I relationship and reduced spike-frequency adaptation, reproducing the changes observed in these parameters during fictive swimming. Application of spiperone, a serotonin antagonist, significantly increased the sAHP amplitude during fictive swimming but had no significant effect on F-I slope or adaptation. Because serotonin may act in part through reduction of calcium currents, the effect of calcium-free solution (cobalt substituted for calcium) was tested in the quiescent spinal cord. Similar to fictive swimming and serotonin application, the calcium-free solution significantly reduced the sAHP amplitude, the slope of the F-I relationship, and spike-frequency adaptation. These results suggest that there are significant changes in the firing properties of motoneurons during fictive swimming compared with the quiescent state, and it is possible that these changes may be attributed in part to the endogenous release of serotonin acting via reduction of calcium currents.

scholarly journals Desensitization of Gamma Aminobutyric Acid (GABA) Receptors in Muscle Fibers of the Crab Cancer borealis

1970 ◽  
Vol 56 (1) ◽  
pp. 33-45 ◽  
Author(s):  
René Epstein ◽  
Harry Grundfest
Keyword(s):  
Gaba Receptors ◽  
Muscle Fibers ◽  
Secretory Activity ◽  
Input Resistance ◽  
Aminobutyric Acid ◽  
Inhibitory Synapses ◽  
Gamma Aminobutyric Acid ◽  
Cancer Borealis ◽  
Conductance Increase ◽  
Excitatory Transmitter

Carcinus muscle fibers respond to γ-aminobutyric acid (GABA) with a conductance increase that subsides rather rapidly. In the larger fibers which have low input resistance the decrease may disappear within 2 min. The inhibition of the excitatory postsynaptic potentials (EPSP's) by GABA nevertheless persists as long as the drug is applied. The subsidence of the increased conductance indicates that the membrane of the inhibitory synapses has become desensitized to GABA. The persistence of inhibition of the EPSP's appears to be due to an action of the drug on the presynaptic terminals of the excitatory axons which reduces or blocks the secretory activity that releases the excitatory transmitter.

Modulation of calcium currents and membrane properties by substance P in the lamprey spinal cord

2013 ◽  
Vol 110 (2) ◽  
pp. 286-296 ◽  
Author(s):  
Carolina Thörn Pérez ◽  
Russell H. Hill ◽  
Sten Grillner
Keyword(s):  
Spinal Cord ◽  
Substance P ◽  
Calcium Channels ◽  
Calcium Channel ◽  
Input Resistance ◽  
Reciprocal Inhibition ◽  
Calcium Currents ◽  
Membrane Properties ◽  
Fictive Locomotion ◽  
Burst Frequency

Substance P is endogenously released within the locomotor network of the adult lamprey, accelerates the burst frequency of fictive locomotion, and reduces the reciprocal inhibition. Previous studies have shown that dopamine, serotonin, and GABA regulate calcium channels, which control neurotransmitter release, action potential duration, and slow afterhyperpolarization (sAHP). Here we examine the effect of substance P on calcium channels in motoneurons and commissural interneurons using whole cell patch clamp in the lamprey spinal cord. This study analyzed the effects of substance P on calcium currents activated in voltage clamp. We examined the calcium-dependent sAHP in current clamp, to determine the involvement of three calcium channel subtypes modulated by substance P. The effects of substance P on membrane potential and during N-methyl-d-aspartic acid (NMDA) induced oscillations were also analyzed. Depolarizing voltage steps induced inward calcium currents. Substance P reduced the currents carried by calcium by 61% in commissural interneurons and by 31% in motoneurons. Using specific calcium channel antagonists, we show that substance P reduces the sAHP primarily by inhibiting N-type (CaV2.2) channels. Substance P depolarized both motoneurons and commissural interneurons, and we present evidence that this occurs due to an increased input resistance. We also explored the effects of substance P on NMDA-induced oscillations in tetrodotoxin and found it caused a frequency increase. Thus the reduction of calcium entry by substance P and the accompanying decrease of the sAHP amplitude, combined with substance P potentiation of currents activated by NMDA, may both contribute to the increase in fictive locomotion frequency.

scholarly journals Cellular and Synaptic Actions of Acetylcholine in the Lamprey Spinal Cord

2008 ◽  
Vol 100 (2) ◽  
pp. 1020-1031 ◽  
Author(s):  
Katharina A. Quinlan ◽  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Input Resistance ◽  
Local Application ◽  
Spinal Motoneurons ◽  
Muscarinic Agonists ◽  
Spinal Neurons ◽  
Cholinergic Interneurons ◽  
Retrograde Filling ◽  
Feedback Pathway

This study investigated cellular and synaptic mechanisms of cholinergic neuromodulation in the in vitro lamprey spinal cord. Most spinal neurons tested responded to local application of acetylcholine (ACh) with depolarization and decreased input resistance. The depolarization persisted in the presence of either tetrodotoxin or muscarinic antagonist scopolamine and was abolished with nicotinic antagonist mecamylamine, indicating a direct depolarization through nicotinic ACh receptors. Local application of muscarinic ACh agonists modulated synaptic strength in the spinal cord by decreasing the amplitude of unitary excitatory and inhibitory postsynaptic potentials. The postsynaptic response to direct application of glutamate was unchanged by muscarinic agonists, suggesting a presynaptic mechanism. Cholinergic feedback from motoneurons was assessed using stimulation of a ventral root in the quiescent spinal cord while recording intracellularly from spinal motoneurons or interneurons. Mainly depolarizing potentials were observed, a portion of which was insensitive to removal of extracellular Ca2+, indicating electrotonic coupling. Hyperpolarizing potentials were also observed and were attenuated by the glycinergic antagonist strychnine, whereas depolarizing responses were potentiated by strychnine. Mecamylamine also reduced hyperpolarizing responses. The pharmacology of these responses suggests a Renshaw-like feedback pathway in lamprey. Immunohistochemistry for choline acetyltransferase, performed in combination with retrograde filling of motoneurons, demonstrated a population of nonmotoneuron cholinergic cells in the lamprey spinal cord. Thus endogenous cholinergic modulation of the lamprey spinal locomotor network is likely produced by both motoneurons and cholinergic interneurons acting via combined postsynaptic and presynaptic actions.

scholarly journals Design, Synthesis and Enhanced BBB Penetration Studies of L-serine-Tethered Nipecotic Acid-Prodrug

Drug Research ◽  
2020 ◽  
Author(s):  
Meenakshi Dhanawat ◽  
Sumeet Gupta ◽  
Dinesh Kumar Mehta ◽  
Rina Das
Keyword(s):  
Epileptic Activity ◽  
Aminobutyric Acid ◽  
Gaba Uptake ◽  
Nipecotic Acid ◽  
Design Synthesis ◽  
Hydrophilic Nature ◽  
Carrier Mediated Transport ◽  
Ester Prodrug ◽  
Hplc Data

Nipecotic acid is considered to be one of the most potent inhibitors of neuronal and glial-aminobutyric acid (GABA) uptake in vitro. Due to its hydrophilic nature, nipecotic acid does not readily cross the blood-brain barrier (BBB). Large neutral amino acids (LAT1)-knotted nipecotic acid prodrug was designed and synthesized with the aim to enhance the BBB permeation by the use of carrier-mediated transport. The synthesized prodrug was tested in animal models of Pentylenetetrazole (PTZ)-induced convulsions in mice. Further pain studies were carried out followed by neurotoxicity estimation by writhing and rota-rod test respectively. HPLC data suggests that the synthesized prodrug has improved penetration through BBB. Nipecotic acid-L-serine ester prodrug with considerable anti-epileptic activity, and the ability to permeate the BBB has been successfully synthesized. Graphical Abstract.

Properties of visceral primary afferent neurons in the nodose ganglion of the rabbit

1985 ◽  
Vol 54 (2) ◽  
pp. 245-260 ◽  
Author(s):  
C. E. Stansfeld ◽  
D. I. Wallis
Keyword(s):  
Action Potentials ◽  
Input Resistance ◽  
Nodose Ganglion ◽  
Time Dependent ◽  
Membrane Properties ◽  
Resting Potential ◽  
Inward Rectification ◽  
C Cells ◽  
Axonal Conduction ◽  
A Cells

The active and passive membrane properties of rabbit nodose ganglion cells and their responsiveness to depolarizing agents have been examined in vitro. Neurons with an axonal conduction velocity of less than 3 m/s were classified as C-cells and the remainder as A-cells. Mean axonal conduction velocities of A- and C-cells were 16.4 m/s and 0.99 m/s, respectively. A-cells had action potentials of brief duration (1.16 ms), high rate of rise (385 V/s), an overshoot of 23 mV, and relatively high spike following frequency (SFF). C-cells typically had action potentials with a "humped" configuration (duration 2.51 ms), lower rate of rise (255 V/s), an overshoot of 28.6 mV, an after potential of longer duration than A-cells, and relatively low SFF. Eight of 15 A-cells whose axons conducted at less than 10 m/s had action potentials of longer duration with a humped configuration; these were termed Ah-cells. They formed about 10% of cells whose axons conducted above 2.5 m/s. The soma action potential of A-cells was blocked by tetrodotoxin (TTX), but that of 6/11 C-cells was unaffected by TTX. Typically, A-cells showed strong delayed (outward) rectification on passage of depolarizing current through the soma membrane and time-dependent (inward) rectification on inward current passage. Input resistance was thus highly sensitive to membrane potential close to rest. In C-cells, delayed rectification was not marked, and slight time-dependent rectification occurred in only 3 of 25 cells; I/V curves were normally linear over the range: resting potential to 40 mV more negative. Data on Ah-cells were incomplete, but in our sample of eight cells time-dependent rectification was absent or mild. C-cells had a higher input resistance and a higher neuronal capacitance than A-cells. In a proportion of A-cells, RN was low at resting potential (5 M omega) but increased as the membrane was hyperpolarized by a few millivolts. A-cells were depolarized by GABA but were normally unaffected by 5-HT or DMPP. C-cells were depolarized by GABA in a similar manner to A-cells but also responded strongly to 5-HT; 53/66 gave a depolarizing response, and 3/66, a hyperpolarizing response. Of C-cells, 75% gave a depolarizing response to DMPP.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C402-C408 ◽  
Author(s):  
E. P. Burke ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Potential Gradient ◽  
Circular Muscle ◽  
Input Resistance ◽  
Pump Current ◽  
Muscle Layer ◽  
Membrane Properties ◽  
Resting Potential ◽  
Voltage Dependent ◽  
In Cells

Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.

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