Electrical behavior of myenteric neurons in guinea pig distal colon

1988 ◽  
Vol 254 (4) ◽  
pp. G522-G530 ◽  
Author(s):  
P. R. Wade ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Action Potentials ◽  
Distal Colon ◽  
Electrical Behavior ◽  
Myenteric Neurons ◽  
Single Action ◽  
Current Pulses

Intracellular recording was used in vitro to analyze electrophysiological properties of neurons in myenteric ganglia of guinea pig distal colon. The neurons were classified into six types based on their electrical behavior. Type 1 colonic neurons discharged action potentials throughout depolarizing current pulses and were otherwise similar to S/type 1 neurons found in the guinea pig small bowel. The second type had passive and active electrical properties similar to those of AH/type 2 myenteric neurons of the small intestine. These cells discharged only a single spike at the onset of depolarizing current pulses, and the spikes were followed by long-lasting hyperpolarizing afterpotentials. Excitability of the type 2 neurons was enhanced in the presence of elevated Mg2+ and reduced Ca2+, and the spikes were unaffected by tetrodotoxin. Type 3 colonic neurons showed fast synaptic potentials but did not generate action potentials. The majority of neurons were referred to as type 2 colonic neurons. Type 4 neurons discharged single action potentials only at the onset of depolarizing current pulses, and the spikes were not followed by prolonged hyperpolarizing afterpotentials. Unlike type 2 neurons, excitability remained unchanged in the presence of reduced extracellular Ca2+ and elevated Mg2+. Action potentials of type 4 neurons were suppressed or abolished by tetrodotoxin. A group of spontaneously active neurons was classified as type 5 colonic neurons. Type 6 cells were inexcitable and assumed to be glial cells.

Electrophysiological properties of neurons in submucosal ganglia of guinea pig distal colon

1991 ◽  
Vol 260 (6) ◽  
pp. G835-G841 ◽  
Author(s):  
T. Frieling ◽  
H. J. Cooke ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Ganglion Cells ◽  
Distal Colon ◽  
Submucosal Plexus ◽  
Electrophysiological Properties ◽  
Small Intestinal ◽  
Type 3

Intracellular recording methods were used in vitro to study the electrophysiological behavior of neurons in ganglia of the submucosal plexus in the distal colon of the guinea pig. The results revealed subpopulations of submucosal ganglion cells that corresponded to the AH/type 2, S/type 1, type 3, and type 4 subpopulations found elsewhere in the intestine. Electrical behavior of colonic submucosal neurons differed from the myenteric plexus of the colon, rectum, and stomach and the small intestinal submucosal plexus mainly in the relative proportions of the different subpopulations. Regional differences in this respect may be a reflection of functional specialization in the diverse regions of the alimentary canal.

Effects of PACAP on morphologically identified myenteric neurons in guinea pig small bowel

1993 ◽  
Vol 264 (3) ◽  
pp. G414-G421 ◽  
Author(s):  
F. L. Christofi ◽  
J. D. Wood
Keyword(s):  
Small Bowel ◽  
Adenylate Cyclase ◽  
Guinea Pig ◽  
Glial Cells ◽  
Input Resistance ◽  
Myenteric Neurons ◽  
Adenosine Receptor Agonist ◽  
Excitatory Responses

Intracellular microelectrodes were used to examine the actions of pituitary adenylate cyclase-activating peptide (PACAP) on morphologically identified myenteric neurons and glial cells of the guinea pig small bowel. PACAP-27 and PACAP-38 evoked excitatory responses in 96% of after hyperpolarizing (AH)/type 2 neurons. The half-maximal concentration for PACAP-27 was 1.5 nM. The responses consisted of membrane depolarization in association with increased input resistance, suppression of hyperpolarizing afterpotentials, and repetitive spike discharge. Forskolin mimicked the action of PACAP in all AH/type 2 neurons. PACAP excited 36% of S/type 1 neurons. Most of the AH/type 2 neurons had Dogiel II morphology, whereas the S/type 1 neurons were uniaxonal with morphology characteristics of Dogiel I or filamentous neurons. No glial cells responded to PACAP. A selective A1 adenosine receptor agonist blocked the excitatory action of PACAP, and this was reversed by a selective A1 antagonist. The results suggest that excitatory PACAP receptors and inhibitory adenosine A1 receptors are linked to adenylate cyclase in AH/type 2 myenteric neurons.

Synaptic behavior of myenteric neurons in guinea pig distal colon

1988 ◽  
Vol 255 (2) ◽  
pp. G184-G190 ◽  
Author(s):  
P. R. Wade ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Input Resistance ◽  
Distal Colon ◽  
Bathing Medium ◽  
Myenteric Neurons ◽  
Fiber Tracts ◽  
Slow Rise ◽  
Domain 3 ◽  
Myenteric Ganglia

Intracellular recording methods were used in vitro to analyze the synaptic behavior of neurons in myenteric ganglia of guinea pig distal colon. Fast excitatory postsynaptic potentials (EPSPs) were observed in a variety of types of colonic neurons. Both spontaneous and stimulus-evoked EPSPs were abolished or suppressed by addition of hexamethonium, tetrodotoxin, or elevation of Mg2+ and reduction of Ca2+ in the bathing medium. Individual neurons usually received inputs from several fiber tracts and multiple EPSPs were sometimes evoked by electrical stimulation of single-fiber tracts. Stimulus-evoked fast EPSPs were always of greater amplitude, longer duration, and longer decay time than were spontaneous fast EPSPs in the same neurons. No rundown of the fast EPSPs occurred during prolonged stimulation at frequencies up to 10 Hz. Repetitive stimulation evoked slow depolarizing potentials (slow EPSPs) in 25% of the neurons. Characteristics of the slow EPSPs were 1) slow rise times, 2) duration in the seconds time domain, 3) enhanced excitability, 4) increased input resistance, and 5) reduction of hyperpolarizing after-potentials. In general, the variety of synaptic potentials and the properties of the events were the same as found in myenteric neurons of the guinea pig small bowel. Compared with synaptic behavior of small intestinal myenteric neurons, the notable differences were absence of the rundown phenomenon for fast EPSPs in the colonic neurons and a greater incidence of spontaneously occurring fast EPSPs.

Membrane properties and synaptic responses of the guinea pig nucleus accumbens neurons in vitro

1989 ◽  
Vol 61 (4) ◽  
pp. 769-779 ◽  
Author(s):  
N. Uchimura ◽  
H. Higashi ◽  
S. Nishi
Keyword(s):  
Membrane Potential ◽  
Nucleus Accumbens ◽  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Reversal Potential ◽  
Membrane Properties ◽  
Current Pulses ◽  
Synaptic Responses

1. The membrane properties and synaptic responses of guinea pig nucleus accumbens neurons in vitro were studied with intracellular recording methods. 2. The population of neurons could be divided into groups of low (20-60 M omega, average 46.5 M omega) and high (60-180 M omega, average 96.5 M omega) input resistance. The resting membrane potential in both groups was approximately -70 mV. 3. Other membrane properties were quite similar in both groups. Inward rectification occurred at potentials more negative than -80 mV; this was blocked by Cs+ (2 mM). Membrane potential oscillations were observed at potentials between -65 and -55 mV; these were blocked by tetrodotoxin (TTX, 0.5 microM). Outward rectification occurred at potentials less negative than -45 mV; this was depressed by tetraethylammonium (TEA, 10 mM). 4. Action potentials elicited by small depolarizing current pulses (2-5 ms, 0.3-0.5 nA) were approximately 95 mV in amplitude and 1.0 ms in duration. The afterhyperpolarization following each action potential was less than 30 ms in duration, and no accommodation of action-potential discharge was seen at frequencies up to 40 Hz. The action potentials were reversibly blocked by TTX (0.3 microM). In addition, TTX-insensitive, Ca2+-dependent spikes were evoked by passing larger and more prolonged current pulses (greater than 40 ms, greater than 0.5 nA) across the membrane. 5. Focal electrical stimulation of the slice surface with low intensity (1 ms, less than 10 V) elicited excitatory postsynaptic potentials (EPSPs) in neurons of both high- and low-resistance groups. The reversal potential (+10.2 mV) for the EPSPs was close to the reversal potential (+7.7 mV) of the responses to glutamate applied in the superfusing solution. The N-methyl-D-aspartic acid (NMDA) receptor antagonists, D-alpha-aminoadipic acid (1 mM) and DL-2-amino-5-phosphonovaleric acid (DL-APV, 250 microM), reversibly depressed the EPSP; the glutamate uptake inhibitor, L-aspartic acid-beta-hydroxamate (50 microM), or removal of Mg2+ from the superfusate, augmented the EPSP. 6. When the intensity of the focal stimulus was increased (1 ms, greater than or equal to 10 V), a second larger depolarizing response (duration, 800 ms to 2 s) could be evoked in addition to the smoothly graded EPSP. This was seen only in cells of the high-resistance group (90-130 M omega).(ABSTRACT TRUNCATED AT 400 WORDS)

Histamine receptors on submucous neurons in guinea pig colon

1993 ◽  
Vol 264 (1) ◽  
pp. G74-G80 ◽  
Author(s):  
T. Frieling ◽  
H. J. Cooke ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Action Potentials ◽  
Acetylcholine Release ◽  
Input Resistance ◽  
Distal Colon ◽  
Intracellular Microelectrodes ◽  
Selective Agonists ◽  
Nicotinic Synapses

Intracellular microelectrodes were used to investigate the actions of histamine in the submucous plexus of the distal colon of the guinea pig. Three effects resulted from application of histamine to submucous neurons. The first was membrane depolarization associated with increased input resistance and augmented excitability. The second was presynaptic suppression of acetylcholine release at nicotinic synapses. The third occurred during long-term application and consisted of recurrent trains of action potentials associated with periodic depolarization of membrane potential. Pharmacological analysis, with selective agonists and antagonists, suggested mediation of the first and third response by postsynaptic histamine H2 receptors. The second response was mediated by presynaptic histamine H3 receptors. These actions of histamine represent a mechanism for neuroimmune signaling between mucosal mast cells and submucous neurons in gastrointestinal type 1 hypersensitivity reactions to allergens.

Synaptic transmission in submucosal ganglia of guinea pig distal colon

1991 ◽  
Vol 260 (6) ◽  
pp. G842-G849 ◽  
Author(s):  
T. Frieling ◽  
H. J. Cooke ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Ganglion Cells ◽  
Input Resistance ◽  
Distal Colon ◽  
Presynaptic Muscarinic Receptors ◽  
The Neural Networks ◽  
Type 3 ◽  
Prolonged Response

Intracellular electrical recording was used to investigate synaptic behavior of ganglion cells in the neural networks of the submucosal plexus of the guinea pig distal colon. Fast excitatory postsynaptic potentials (EPSPs), mediated by nicotinic receptors, were found in all S/type 1 neurons, 70% of AH/type 2, 75% of type 3, and 95% of type 4 neurons. Slow EPSPs were characterized by membrane depolarization, increased input resistance, enhanced action potential discharge, and suppression of hyperpolarizing afterpotentials in 64% of the S/type 1 neurons, 74% of AH/type 2, 31% of type 3, and 70% of type 4 neurons. Micropressure application of acetylcholine evoked a two-component depolarizing response consisting of an initial transient with decreased input resistance followed by a prolonged depolarization associated with increased input resistance. The transient response was suppressed by nicotinic-blocking drugs. Muscarinic antagonists suppressed the prolonged response. Acetylcholine acted also at presynaptic muscarinic receptors to suppress stimulus-evoked fast EPSPs. No stimulus-evoked inhibitory synaptic potentials were observed. Norepinephrine, applied by microejection, acted at alpha 2-adrenoceptors to hyperpolarize the membrane potential in association with decreased neuronal input resistance.

Actions of reactive oxygen species on AH/type 2 myenteric neurons in guinea pig distal colon

2000 ◽  
Vol 279 (5) ◽  
pp. G893-G902 ◽  
Author(s):  
S. Wada-Takahashi ◽  
K. Tamura
Keyword(s):  
Reactive Oxygen Species ◽  
Guinea Pig ◽  
Late Onset ◽  
Reactive Oxygen ◽  
Distal Colon ◽  
Membrane Depolarization ◽  
Oxygen Species ◽  
Membrane Hyperpolarization ◽  
Myenteric Neurons

With conventional intracellular recording methods, we investigated the mechanism of actions of reactive oxygen species (ROS) derived from hypoxanthine and xanthine oxidase (HX/XO) reactions on AH/type 2 myenteric neurons in the guinea pig distal colon. Of the 54 neurons to which HX/XO was applied, 32 neurons showed a transient membrane hyperpolarization(s) followed by a long-lasting membrane depolarization. Two additional groups of 10 myenteric neurons exhibited only a membrane hyperpolarization(s) or a late-onset membrane depolarization, respectively, and the remaining two neurons did not show any response to HX/XO. Analysis of changes of the input resistance induced by HX/XO indicated that suppression and augmentation of the conductance of Ca2+-dependent K+ channels are the ionic mechanisms underlying the membrane hyperpolarization and depolarization, respectively. The effects of HX/XO on myenteric neurons were mimicked by application of caffeine or H2O2. The results suggest that OH·, but neither H2O2 nor O2 · −, is responsible for HX/XO-induced responses. The intracellular Ca2+ store may be the acting site of ROS in colonic AH/type 2 neurons.

scholarly journals Effect of Different Fermentation Condition on Estimated Glycemic Index, In Vitro Starch Digestibility, and Textural and Sensory Properties of Sourdough Bread

Foods ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 514
Author(s):  
Hilal Demirkesen-Bicak ◽  
Muhammet Arici ◽  
Mustafa Yaman ◽  
Salih Karasu ◽  
Osman Sagdic
Keyword(s):  
Glycemic Index ◽  
Sensory Properties ◽  
Starch Digestibility ◽  
In Vitro Starch Digestibility ◽  
Whole Wheat ◽  
Sourdough Bread ◽  
Estimated Glycemic Index

This study aimed to evaluate the influence of sourdough fermentation on the estimated glycemic index (eGI), in vitro starch digestibility, and textural and sensory properties of eight experimentally prepared sourdough breads. Wheat and whole wheat flour bread samples were produced under different fermentation conditions (25 °C and 30 °C) and fermentation methods (type-1 and type-2). In type-1 fermentation, sourdough was obtained via spontaneous fermentation. Indigenous strains (Lactobacillus brevis ELB99, Lactiplantibacillus plantarum ELB75, and Saccharomyces cerevisiae TGM55) were used for type-2 fermentation. Fermentation type and temperature significantly affected eGI, the hydrolysis index (HI), the starch fraction, and the textural properties of the samples (p < 0.05). The resistant starch (RS) content increased after fermentation, while rapidly digestible starch (RDS), HI, and eGI decreased. RS values were significantly higher in type-2 than in type-1 at the same temperature for both flour types (p < 0.05). At 25 °C, RS values were higher in both fermentation types. In the white flour samples, eGI values were in the range of 60.8–78.94 and 62.10–78.94 for type-1 and type-2, respectively. The effect of fermentation type on eGI was insignificant (p < 0.05). In the whole flour samples, fermentation type and temperature significantly affected eGI (p < 0.05). The greatest eGI decreases were in whole wheat sourdough bread at 30 °C using type-2 (29.74%). The 30 °C and type-2 samples showed lower hardness and higher specific volume. This study suggests that fermentation type and temperature could affect the eGI and the textural and sensory properties of sourdough bread, and these factors should be considered during bread production. The findings also support the consumption of wheat and whole wheat breads produced by type-2 fermentation due to higher RS and slowly digestible starch (SDS) and lower RDS and eGI values.

scholarly journals First Report ofEurycoma longifoliaJack Root Extract Causing Relaxation of Aortic Rings in Rats

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Bae Huey Tee ◽  
See Ziau Hoe ◽  
Swee Hung Cheah ◽  
Sau Kuen Lam
Keyword(s):  
Erectile Function ◽  
Receptor Activation ◽  
Root Extract ◽  
Ang Ii ◽  
Angiotensin I ◽  
Eurycoma Longifolia ◽  
Vasodilatory Effect

AlthoughEurycoma longifoliahas been studied for erectile function, the blood pressure- (BP-) lowering effect has yet to be verified. Hence, this study aims at investigating the BP-lowering properties of the plant with a view to develop an antihypertensive agent that could also preserve erectile function. Ethanolic root extract was partitioned by hexane, dichloromethane (DCM), ethyl acetate, butanol, and water. The DCM fraction, found to be potent in relaxing phenylephrine- (PE-) precontracted rat aortic rings, was further purified by column chromatography. Subfraction DCM-II, being the most active in relaxing aortae, was studied for effects on the renin-angiotensin and kallikrein-kinin systems in aortic rings. The effect of DCM-II on angiotensin-converting enzyme (ACE) activity was also evaluatedin vitro. Results showed that DCM-II reduced (p<0.05) the contractions evoked by angiotensin I and angiotensin II (Ang II). In PE-precontracted rings treated with DCM-II, the Ang II-induced contraction was attenuated (p<0.05) while bradykinin- (BK-) induced relaxation enhanced (p<0.001).In vitro, DCM-II inhibited (p<0.001) the activity of ACE. These data demonstrate that the vasodilatory effect of DCM-II appears to be mediatedviainhibition of Ang II type 1 receptor and ACE as well as enhancement of Ang II type 2 receptor activation and BK activity.

scholarly journals Differential Activation of CD8+Tumor-Specific Tc1 and Tc2 Cells by an IL-10-Producing Murine Plasmacytoma

1998 ◽  
Vol 6 (3-4) ◽  
pp. 331-342 ◽  
Author(s):  
Christoph Specht ◽  
Hans-Gerd Pauels ◽  
Christian Becker ◽  
Eckehart Kölsch
Keyword(s):  
T Cells ◽  
Immune Responses ◽  
Tumor Cells ◽  
T Cell Subsets ◽  
Early Stages ◽  
Specific Tolerance

The involvement of counteractiveCD8+T-cell subsets during tumor-specific immune responses was analyzed in a syngeneic murine plasmacytoma model.CD8+Tc cells against the immunogenic IL-10-producing BALB/c plasmacytoma ADJ-PC-5 can be easily induced by immunization of BALB/c mice with X-irradiated ADJ-PC-5 tumor cellsin vivoandin vitro. However, the failure of recipient mice to mount a protective Tc response against the tumor during early stages of a real or simulated tumor growth is not due to immunological ignorance, but depends on the induction of tumor-specific tolerance, involving a population of tumorinducedCD8+T cells that are able to inhibit the generation of tumor-specific Tc cells in a primary ADJ-PC-5-specific MLTC, using IFN-γas a suppressive factor. Whereas most longterm cultivated CD8+ADJ-PC-5-specific Tc lines produce type-1 cytokines on stimulation, at least two of them, which were derived from a primary MLTC, display a type-2 cytokine spectrum. Furthermore, the primaryin vitroTc response against ADJ-PC-5 cells shows characteristics of a Tc2 response. The Tc response is strictly depending on tumor-derived IL-10.CD8+Tc cells that are induced in a primary MLTC do not produce IFN-γ, and the tumor-specific Tc response is enhanced by IL-4 but suppressed by IFN-γor IL-12. In contrast, ADJ-PC- 5-specificCD8+Tc cells from immunized mice are IFN-γproducing Tc1 cells. Since the primaryin vitroTc response against the tumor is suppressed even by the smallest numbers of irradiated ADJ-PC-5-specific Tc1 cells via IFN-γthese Tc1 cells behave similar to the suppressiveCD8+T cells that are induced during early stages of ADJ-PC-5 tumorigenesis.

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