Ionic bases of resting and action potentials in salivary gland acinar cells of the snail Helisoma

1980 ◽  
Vol 84 (1) ◽  
pp. 213-225
Author(s):  
R. D. Hadley ◽  
A. D. Murphy ◽  
S. B. Kater
Keyword(s):  
Salivary Gland ◽  
Action Potentials ◽  
Resting Potential ◽  
Potassium Ions ◽  
Small Contribution ◽  
Salivary Gland Cells ◽  
Electrogenic Sodium Pump ◽  
Membrane Permeabilities ◽  
Stimulus Secretion Coupling ◽  
Intracellular Potassium Concentration

Values for resting and action potentials of Helisoma salivary gland cells are much the same as in most neurones and muscle cells. The resting potential is primarily due to the distribution of potassium ions across the membrane, with a small contribution by an electrogenic sodium pump. Estimated values for intracellular potassium concentration and the relative membrane permeabilities to sodium and potassium ions correspond to similar estimates in other excitable tissues. The inward current of the salivary gland action potential is carried predominantly by calcium ions and possibly serves as a mechanism of calcium entry for stimulus-secretion coupling.

scholarly journals Calcium-Dependent Action Potentials in Giant Salivary Gland Cells of the Leech: Haementeria Ghilianii: Calcium Removal Induces Dependence on Sodium

1988 ◽  
Vol 138 (1) ◽  
pp. 431-453
Author(s):  
WERNER A. WUTTKE ◽  
MICHAEL S. BERRY
Keyword(s):  
Salivary Gland ◽  
Membrane Potential ◽  
Action Potentials ◽  
Electrophysiological Study ◽  
Resting Membrane Potential ◽  
Small Contribution ◽  
Gland Cells ◽  
Na Pump ◽  
Salivary Gland Cells ◽  
Electrogenic Na Pump

1. An electrophysiological study was made of the giant, non-coupled salivary gland cells of the leech Haementeria ghilianii (de Filippi, 1849). 2. Resting membrane potential (−40 mV to −80 mV) was primarily dependent on K+, with a small contribution from a Na+ conductance and an electrogenic Na+ pump. Resting Cl− permeability was low. 3. The cells generated overshooting action potentials (70–110 mV, 100–400 ms) which appeared to be mediated exclusively by Ca2+ because they were unaffected by removal of external Na+ and were blocked by 5 mmoll−1 Co2+. 4. Removal of external Ca2+ and addition of 1 mmoll−1 EGTA produced spontaneous action potentials of reduced amplitude (peaking at about 0 mV) and greatly increased duration [typically tens of seconds but sometimes resulting in sustained depolarizations (plateau potentials) extending up to 30min or more]. Action potential amplitude was then dependent on external Na+ concentration, and action potentials were abolished by removal of Na+. The responses were locked by 5 mmoll−1 Co2+, indicating that they were produced by Na+ flowing through Ca2+ channels. 5. Addition of micromolar concentrations of Ca2+ to Ca2+ free saline decreased spike duration and amplitude, suggesting a competition between Na+ and Ca2+. 6. An electrogenic Na+ pump was activated by removal of Ca2+, presumably as result of the influx of Na+ during spiking; this produced large increases in membrane potential which occurred spontaneously or when Ca2+ was reintroduced. 7. In normal saline, spike overshoot and duration were increased when the temperature was lowered by 10°C, whereas in Ca2+-free solution, they were reduced by this change. This suggests that the Ca2+ channel may be differentially affected by cooling, depending on the presence or absence of Ca+

An Investigation of the Electrogenic Sodium Pump in Snail Neurones, Using the Constant-Field Theory

1969 ◽  
Vol 51 (1) ◽  
pp. 181-201
Author(s):  
R. B. MORETON
Keyword(s):  
Field Equation ◽  
Sodium Pump ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Constant Field ◽  
Sodium Ions ◽  
Intracellular Potassium ◽  
Electrogenic Sodium Pump ◽  
Snail Neurones ◽  
Intracellular Potassium Concentration

1. Sodium ions injected into giant neurones of Helix aspersa by diffusion from low-resistance microelectrodes caused hyperpolarization of the cells. Under these conditions the behaviour of the resting potential could be described by a modified ‘constant-field’ equation, including a term representing the effect of a potassiumsensitive, electrogenic sodium pump. 2. Exposure to potassium-free solution, ouabain or cyanide abolished the hyperpolarization, and caused a gradual fall in the intracellular potassium concentration, as estimated from the constant-field equation. 3. Assuming that this fall was due to replacement of intracellular potassium by injected sodium ions, it was possible to calculate the rates of injection and pumping of sodium ions, and, using the measured membrane resistance of the cell, the hyperpolarization which the sodium pump could cause, if it were electrogenic. 4. This was related to the observed hyperpolarization, supporting the view that the latter was caused by stimulation of the electrogenic sodium pump.

Helping students to understand that outward currents depolarize cells.

1999 ◽  
Vol 276 (6) ◽  
pp. S62
Author(s):  
M Stewart
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Action Potentials ◽  
Building Blocks ◽  
Resting Potential ◽  
Potassium Ions ◽  
General Statement ◽  
Outward Currents ◽  
Excitable Membranes ◽  
A Cell

The physiology of excitable membranes is a fundamental topic in neuroscience and physiology courses at graduate and undergraduate levels. From the building blocks of ionic gradients and membrane channels whose permeability is selective and variable, we build the concepts of resting potential, action potential, and propagation in neurons and muscle fibers. Many students have an intuitive understanding of the movements of ions and the associated changes in membrane potential. For example, potassium ions leaving a cell through potassium-selective channels become unbalanced positive charges on the outside of the cell (and leave unbalanced negative charges on the inside), thus producing a potential across the membrane with the inside negative with respect to the outside. Later, when we discuss the local circuit currents that underlie propagation or the basis for extracellular stimulation, we make the general statement that "outward currents depolarize cells." Students respond with utter disbelief. Two simple additions to a discussion of membranes are suggested that permit the formulation of a consistent set of rules that apply to everything from the resting and action potentials of nerve and muscle through synaptic potentials and stimulation techniques.

scholarly journals Excitability and secretory activity in the salivary gland cells of jawed leeches (Hirudinea: Gnathobdellida)

1988 ◽  
Vol 137 (1) ◽  
pp. 89-105
Author(s):  
C. G. Marshall ◽  
C. M. Lent
Keyword(s):  
Nervous System ◽  
Salivary Gland ◽  
Action Potentials ◽  
Impulse Activity ◽  
Average Rate ◽  
Secretory Activity ◽  
Calcium Dependent ◽  
Gland Cells ◽  
Salivary Gland Cells ◽  
Retzius Cells

Thousands of salivary cells fill the interstices throughout the anterior ends of jawed leeches. The somata are large (30–200 micron in diameter). They project single processes (ductules) into the three jaws, and were found to fire overshooting action potentials of 50–85 mV amplitude and 100–200 ms duration at low spontaneous rates. The action potentials were not detected in the presence of cobalt (10 mmol l-1), but could be recorded when sodium was absent from the Ringer, so they appear to be calcium-dependent. Salivary material is transported by the long processes of these unicellular glands and secreted into ducts which alternate with paired teeth on the jaws. Secretion is activated reliably by 10(−6) mol l-1 serotonin, but not by other neurotransmitters found in the leech nervous system. Each jaw secretes at an average rate of 230 nl min-1 in the presence of serotonin, and secretion is completely abolished by cobalt. Perfusion with serotonin excites the salivary gland cells into impulse activity, and often evokes bursting. Impulse activity of the peripherally projecting, serotonergic Retzius cells evokes both depolarizations and action potentials in the salivary gland cells. In jawed leeches, central neurones appear to control salivation by a peripheral release of serotonin. This neurotransmitter evokes calcium-dependent action potentials and calcium, in turn, stimulates secretion.

Control of the salivary glands of Helisoma by identified neurones

1978 ◽  
Vol 72 (1) ◽  
pp. 91-106
Author(s):  
S. B. Kater ◽  
A. D. Murphy ◽  
J. R. Rued
Keyword(s):  
Salivary Gland ◽  
Epithelial Cells ◽  
Salivary Glands ◽  
Action Potentials ◽  
Neuromuscular Junctions ◽  
Exocrine Gland ◽  
Neural Regulation ◽  
Buccal Ganglion ◽  
Salivary Gland Cells ◽  
Glandular Cells

The neural regulation of an exocrine gland was investigated at the level of identified effector neurones. The salivary gland neuroeffector system of Helisoma consists of a pair of acinous glands innervated by two symmetrically located, identified buccal ganglion neurones (4R and 4L). Neurones 4R and 4L usually are electrically coupled and display synchronous activity. Action potentials in these neurones elicit EPSPs and action potentials in epithelial cells of the salivary glands. Spontaneous miniature potentials similar to those seen at neuromuscular junctions can be recorded from many of the glandular cells. Neurones 4R and rL, and thus also salivary gland cells, can display bursts of action potentials phase-locked with those seen in buccal mass motoneurones during feeding.

scholarly journals Isoproterenol evokes extracellular Ca2+ spikes due to secretory events in salivary gland cells.

1998 ◽  
Vol 273 (17) ◽  
pp. 10806
Author(s):  
Pavel Belan ◽  
Julie Gardner ◽  
Oleg Gerasimenko ◽  
Chris Lloyd Mills ◽  
Ole H. Petersen ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Gland Cells ◽  
Salivary Gland Cells

scholarly journals Trp1, a candidate protein for the store-operated Ca2+ influx mechanism in salivary gland cells.

2000 ◽  
Vol 275 (13) ◽  
pp. 9890-9891
Author(s):  
Xibao Liu ◽  
Weiching Wang ◽  
Brij B. Singh ◽  
Timothy Lockwich ◽  
Julie Jadlowiec ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Gland Cells ◽  
Salivary Gland Cells ◽  
Candidate Protein

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)

Sign in / Sign up

Export Citation Format

Share Document