Effects of active sodium transport on current-voltage relationship of toad bladder

1970 ◽  
Vol 219 (1) ◽  
pp. 234-245 ◽  
Author(s):  
MM Civan
Keyword(s):  
Sodium Transport ◽  
Toad Bladder ◽  
Active Sodium ◽  
Active Sodium Transport ◽  
Current Voltage ◽  
Relationship Of ◽  
Current Voltage Relationship ◽  
Voltage Relationship

scholarly journals Plasticity of calcium-permeable AMPA glutamate receptors in Pro-opiomelanocortin neurons

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Shigetomo Suyama ◽  
Alexandra Ralevski ◽  
Zhong-Wu Liu ◽  
Marcelo O Dietrich ◽  
Toshihiko Yada ◽  
...  
Keyword(s):  
Food Deprivation ◽  
High Fat Diet ◽  
Receptor Complex ◽  
High Fat ◽  
Fasted State ◽  
Linear Current ◽  
Current Voltage ◽  
Relationship Of ◽  
Current Voltage Relationship ◽  
Voltage Relationship

POMC neurons integrate metabolic signals from the periphery. Here, we show in mice that food deprivation induces a linear current-voltage relationship of AMPAR-mediated excitatory postsynaptic currents (EPSCs) in POMC neurons. Inhibition of EPSCs by IEM-1460, an antagonist of calcium-permeable (Cp) AMPARs, diminished EPSC amplitude in the fed but not in the fasted state, suggesting entry of GluR2 subunits into the AMPA receptor complex during food deprivation. Accordingly, removal of extracellular calcium from ACSF decreased the amplitude of mEPSCs in the fed but not the fasted state. Ten days of high-fat diet exposure, which was accompanied by elevated leptin levels and increased POMC neuronal activity, resulted in increased expression of Cp-AMPARs on POMC neurons. Altogether, our results show that entry of calcium via Cp-AMPARs is inherent to activation of POMC neurons, which may underlie a vulnerability of these neurons to calcium overload while activated in a sustained manner during over-nutrition.

Capsaicin and nicotine both activate a subset of rat trigeminal ganglion neurons

1996 ◽  
Vol 270 (6) ◽  
pp. C1807-C1814 ◽  
Author(s):  
L. Liu ◽  
S. A. Simon
Keyword(s):  
Trigeminal Ganglion ◽  
Acetylcholine Receptors ◽  
Ganglion Cells ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons ◽  
Relationship Of ◽  
Current Voltage Relationship ◽  
Voltage Relationship

Nicotine and capsaicin produce many similar physiological responses that include pain, irritation, and vasodilation. To determine whether neuronal nicotine acetylcholine receptors (nAChR) are present on capsaicin-sensitive neurons, whole cell patch-clamp recordings were performed on rat trigeminal ganglion cells. It was found that approximately 20% of the total number of neurons tested was activated by both 100 microM nicotine and 1 nM capsaicin. Other subsets of neurons were activated by only one of these compounds, whereas a fourth subset was not activated by either compound. At -60 mV, the magnitude of the capsaicin-activated currents was about three times larger than the magnitude of the nicotine-activated currents. The current-voltage relationship of the nAChR exhibited marked rectification, such that for voltages > or = 0 mV the current was essentially zero. In contrast, the current-voltage relationship of the capsaicin-activated current was ohmic from +/- 60 mV. These data indicate the existence of subsets of capsaicin-sensitive afferent neurons.

scholarly journals The Electrical Characteristics of Active Sodium Transport in the Toad Bladder

1963 ◽  
Vol 46 (3) ◽  
pp. 491-503 ◽  
Author(s):  
Howard S. Frazier ◽  
Alexander Leaf
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Diffusion Potential ◽  
Toad Bladder ◽  
Chloride Diffusion ◽  
Active Sodium ◽  
High Potassium ◽  
Potential Step ◽  
Active Sodium Transport ◽  
Wide Range

The mechanism responsible for active sodium transport in the urinary bladder of the toad appears to be located at the serosal boundary of the epithelial cell layer of the bladder. Studies of the potential step observed at the serosal boundary in the open-circuited state were undertaken in an attempt to define the factors responsible for its production. Glass micropipettes were used to measure the serosal potential step in bladders exposed on the serosal side to solutions of high potassium or of high potassium and low chloride concentration. Observed potentials exceed the maximum values which would have been expected if the serosal potential step were a potassium or chloride diffusion potential. Measurements of net cation flux exclude the possibility of a diffusion potential at this border due to the passive movement of any anionic species. The observed independence of transbladder potential and short-circuit current from the pH of the serosal medium over a wide range of pH makes it unlikely that the observed serosal potential step is a hydrogen ion diffusion potential. We conclude that the active sodium transport mechanism in toad bladder is "electrogenic."

On the current-voltage relationship of the magnetospheric generator at intermediate spatial scales

1986 ◽  
Vol 13 (6) ◽  
pp. 495-498 ◽  
Author(s):  
J. F. Vickrey ◽  
R. C. Livingston ◽  
N. B. Walker ◽  
T. A. Potemra ◽  
R. A. Heelis ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Current Voltage ◽  
Relationship Of ◽  
Current Voltage Relationship ◽  
Voltage Relationship

scholarly journals THE EFFECT OF CALCIUM WITHDRAWAL ON THE STRUCTURE AND FUNCTION OF THE TOAD BLADDER

1965 ◽  
Vol 25 (3) ◽  
pp. 195-209 ◽  
Author(s):  
Richard M. Hays ◽  
Bayla Singer ◽  
Sasha Malamed
Keyword(s):  
Epithelial Cells ◽  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Structure And Function ◽  
Toad Bladder ◽  
Active Sodium ◽  
Bathing Medium ◽  
Active Sodium Transport ◽  
And Function

Previous reports have indicated that calcium is necessary to support active sodium transport by the toad bladder, and may be required as well in the action of vasopressin on both toad bladder and frog skin. The structure and function of the toad bladder has been studied in the absence of calcium, and a reinterpretation of the previous findings now appears possible. When calcium is withdrawn from the bathing medium, epithelial cells detach from one another and eventually from their supporting tissue. The short-circuit current (the conventional means of determining active sodium transport) falls to zero, and vasopressin fails to exert its usual effect on short-circuit current and water permeability. However, employing an indirect method for the estimation of sodium transport (oxygen consumption), it is possible to show that vasopressin exerts its usual effect on Qoo2 when sodium is present in the bathing medium. Hence, it appears that the epithelial cells maintain active sodium transport when calcium is rigorously excluded from the bathing medium, and continue to respond to vasopressin. The failure of conventional techniques to show this can be attributed to the structural alterations in the epithelial layer in the absence of calcium. These findings may provide a model for the physiologic action of calcium in epithelia such as the renal tubule.

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