Transmural fluxes of 5-hydroxytryptamine in guinea pig ileum

1983 ◽  
Vol 244 (4) ◽  
pp. G421-G425 ◽  
Author(s):  
H. J. Cooke ◽  
M. Montakhab ◽  
P. R. Wade ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Ganglion Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Linear Functions ◽  
Guinea Pig Ileum ◽  
Serotonergic Receptors ◽  
Flat Sheet ◽  
Muscularis Externa

Transmural movement of 5-hydroxytryptamine (5-HT) was studied in guinea pig small intestine in vitro in order to test the hypothesis that there is mucosal 5-HT barrier in this species. Segments of guinea pig ileum were mounted as flat sheets in flux chambers or were everted and perfused. Mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of 5-HT were measured in the absence of 5-HT gradients and under open- or short-circuited conditions. The results indicated that substantial transmural movement of 5-HT occurred in these preparations. Both Jm leads to s and Js leads to m were linear functions of the 5-HT concentration over a range of 1-30 microM and were not significantly different in the two directions. Addition of 2,4-dinitrophenol to both sides of the tissue reduced short-circuit current to zero and increased both tissue conductance and unidirectional 5-HT fluxes. These results suggested that the 5-HT fluxes across the guinea pig ileum occurred by passive mechanisms. Fluxes of 5-HT across preparations with the muscularis externa removed were not significantly different from fluxes across intact preparations. Mucosal-to-serosal 5-HT fluxes in everted perfused sacs were comparable with fluxes in the flat-sheet preparations. The data are not consistent with the hypothesis of a "tissue barrier" that functions to prevent 5-HT from reaching serotonergic receptors on enteric ganglion cells or enteroendocrine cells.

Cellular pathways mediating tachykinin-evoked secretomotor responses in guinea pig ileum

1997 ◽  
Vol 273 (5) ◽  
pp. G1127-G1134 ◽  
Author(s):  
W. MacNaughton ◽  
B. Moore ◽  
S. Vanner
Keyword(s):  
Guinea Pig ◽  
Receptor Agonist ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Neurokinin A ◽  
Guinea Pig Ileum ◽  
Cellular Pathways ◽  
20 Nm

This study characterized tachykinin-evoked secretomotor responses in in vitro submucosal and mucosal-submucosal preparations of the guinea pig ileum using combined intracellular and Ussing chamber recording techniques. Superfusion of endogenous tachykinins substance P (SP), neurokinin A (NKA), and neurokinin B depolarized single submucosal neurons and evoked increased short-circuit current ( I sc) responses in Ussing chamber preparations. The NK1-receptor agonist [Sar9,Met(O2)11]SP [50% effective concentration (EC50) = 2 nM] depolarized all submucosal neurons examined. The NK3-receptor agonist senktide (EC50 = 20 nM) depolarized ∼50% of neurons examined, whereas the NK2-receptor agonist [Ala5,β-Ala8]NKA-(4—10) had no effect on membrane potential. [Sar9,Met(O2)11]SP and senktide evoked similar increases in I sc that were tetrodotoxin sensitive (91 and 100%, respectively) and were selectively blocked by the NK1antagonist CP-99,994 and the NK3antagonist SR-142801, respectively. Capsaicin-evoked increases in I sc were significantly inhibited (54%, P < 0.05) by CP-99,994 but not by SR-142801. Neither antagonist inhibited slow excitatory postsynaptic potentials. These findings suggest that tachykinin-evoked secretion in guinea pig ileum is mediated by NK1 and NK3 receptors on submucosal secretomotor neurons and that capsaicin-sensitive nerves release tachykinin(s) that activate the NK1 receptors.

Effects of neurotransmitter release on mucosal transport in guinea pig ileum

1983 ◽  
Vol 245 (6) ◽  
pp. G745-G750 ◽  
Author(s):  
H. J. Cooke ◽  
K. Shonnard ◽  
G. Highison ◽  
J. D. Wood
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Neurotransmitter Release ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Scorpion Venom ◽  
Enteric Neurons ◽  
Sodium Absorption ◽  
Guinea Pig Ileum ◽  
Ileal Mucosa

Scorpion venom (Leiurus quinquestriatus), a substance that evokes neurotransmitter release by depolarizing neurons, was used to activate enteric neurons in short-circuited guinea pig ileum. Scorpion venom increased transmural potential difference and short-circuit current, and this response was similar to the increase that occurred after electrical stimulation of enteric neurons. The stimulus- or venom-evoked response in short-circuit current was abolished by tetrodotoxin. Atropine reduced by 47% the increments in short-circuit current produced by either electrical stimulation or venom. Scorpion venom increased active chloride secretion in short-circuited guinea pig ileal mucosa but had no significant effect on active sodium absorption, residual flux, or total tissue conductance. No morphological changes in transmission electron micrographs of ileal mucosa treated with scorpion venom were evident compared with controls. Alanine caused an increase in short-circuit current in venom-treated tissue that was similar to control values. These results show that scorpion venom mimics the mucosal effects of electrical activation of enteric neurons. These results suggest that a significant component of both scorpion venom action and the response to electrical field stimulation is mediated by neural release of acetylcholine, which activates epithelial muscarinic receptors.

Capsaicin-sensitive afferent nerves activate submucosal secretomotor neurons in guinea pig ileum

1995 ◽  
Vol 269 (2) ◽  
pp. G203-G209 ◽  
Author(s):  
S. Vanner ◽  
W. K. MacNaughton
Keyword(s):  
Guinea Pig ◽  
Ion Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Sensory Nerve ◽  
Nerve Fibers ◽  
Sensory Nerves ◽  
Guinea Pig Ileum ◽  
Secretomotor Neurons

This study examined whether capsaicin-sensitive sensory nerves regulate intestinal ion transport using both Ussing chamber and intracellular recording techniques in in vitro submucosal preparations from the guinea pig ileum. In Ussing chamber studies, serosal application of capsaicin (20 nM-20 microM) evoked a biphasic dose-dependent increase in short-circuit current (Isc) (maximal effective concentration 200 nM and 2 microM, respectively). In chloride-free buffer, capsaicin responses were significantly reduced. Capsaicin evoked little or no response when extrinsic sensory nerve fibers had been surgically removed and tetrodotoxin and low-calcium and high-magnesium solutions blocked responses to capsaicin. In epithelial preparations devoid of submucosal neurons, capsaicin had virtually no effect, suggesting that responses evoked by capsaicin-sensitive nerves result from activation of submucosal secretomotor neurons. Intracellular recordings from single submucosal neurons demonstrated that superfusion with capsaicin (2 microM) depolarized neurons with an associated decreased conductance. Depolarizations were completely desensitized when capsaicin was reapplied, but synaptic inputs were unaffected. This study suggests that capsaicin-sensitive nerves can regulate ion transport in the gastrointestinal tract by release of neurotransmitter(s) that activate submucosal secretomotor neurons.

Effects of the inflammatory mediator prostaglandin D2 on submucosal neurons and secretion in guinea pig colon

1994 ◽  
Vol 266 (1) ◽  
pp. G132-G139 ◽  
Author(s):  
T. Frieling ◽  
C. Rupprecht ◽  
A. B. Kroese ◽  
M. Schemann
Keyword(s):  
Guinea Pig ◽  
Ganglion Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Prostaglandin D2 ◽  
Flux Chamber ◽  
Dose Dependent Increase ◽  
Dose Dependent

Conventional flux chamber and intracellular recording methods were used to investigate the mode of action of prostaglandin D2 (PGD2) on ion transport in muscle-stripped segments of guinea pig colon and on colonic submucosal ganglion cells. Application of PGD2 resulted in a dose-dependent increase in short-circuit current that was reduced by serosal addition of bumetanide, tetrodotoxin, atropine, or piroxicam, but not hexamethonium. Application of PGD2 to submucosal neurons evoked a depolarization of the membrane potential that was associated with an enhanced spike discharge. In AH/type 2 neurons, postspike afterhyperpolarizations were reduced in amplitude and duration. The depolarizing responses to PGD2 were not affected by tetrodotoxin, indicative of a direct effect of PGD2 on the impaled neurons. Whereas fast excitatory postsynaptic potentials (EPSPs) were not affected by PGD2, slow EPSPs were reduced by a presynaptic effect, indicating presynaptic suppression of noncholinergic neurotransmitter release. The study demonstrates that PGD2 acts as a neuromodulator to evoke nerve-mediated chloride secretion, predominantly through activation of cholinergic submucosal neurons. The results further indicate that PGD2 released from lamina propria immune cells during antigenic stimulation may influence mucosal function by altering electrical behavior of submucosal neurons.

Receptors for vasoactive intestinal peptide and secretin on small intestinal epithelial cells

1980 ◽  
Vol 238 (3) ◽  
pp. G190-G196
Author(s):  
H. J. Binder ◽  
G. F. Lemp ◽  
J. D. Gardner
Keyword(s):  
Small Intestine ◽  
Guinea Pig ◽  
Vasoactive Intestinal Peptide ◽  
Binding Sites ◽  
Prostaglandin E1 ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Maximal Effect ◽  
Single Class

Binding of 125I-labeled vasoactive intestinal peptide (VIP) to dispersed enterocytes prepared from guinea pig small intestine was saturable, temperature dependent, and reversible, and reflected interaction of the labeled peptide with a single class of binding sites. Each enterocyte possessed approximately 60,000 binding sites and binding of the tracer to these sites could be inhibited by VIP [concentration for half-maximal effect (Kd), 12 nM] and by secretin (Kd greater than 1 micro M), but not by glucagon, gastrin, cholecystokinin, calcitonin, bombesin, litorin, physalaemin, substance P, eledoisin, serotonin, carbamylcholine, or histamine. With VIP and secretin, there was a close correlation between the relative potency for inhibition of binding of 125I-VIP and that for increasing cellular cAMP. For a given peptide, however, a 10-fold higher concentration was required for half-maximal inhibition of binding than for half-maximal stimulation of cellular cAMP. In addition to inhibiting binding of 125I-VIP and increasing cellular cAMP in enterocytes, secretin caused an increase in short-circuit current across guinea pig small intestine in vitro. Prostaglandin E1 increased cellular cAMP, but did not alter binding of 125I-VIP and the increase in cAMP caused by prostaglandin E1 plus VIP or secretin was equal to the sum of the increase caused by each agent alone.

Electrophysiological properties of guinea pig tracheal epithelium determined by cable analysis

1993 ◽  
Vol 265 (1) ◽  
pp. L38-L44
Author(s):  
T. L. Croxton
Keyword(s):  
Guinea Pig ◽  
Ion Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Tracheal Epithelium ◽  
Sodium Absorption ◽  
Luminal Diameter ◽  
Cable Analysis

Electrophysiological characteristics of guinea pig tracheae were measured in vitro using an adaptation of cable analysis. This method allowed the repeated measurement of luminal diameter and epithelial electrical potential, resistance, and short-circuit current (Isc) during treatments known to affect smooth muscle contraction and epithelial ion transport. Stable values taken 3 h after mounting were as follows: diameter, 2.27 +/- 0.10 mm; potential, -28.3 +/- 2.3 mV; resistance, 327 +/- 30 omega.cm2; and Isc, 91.2 +/- 6.8 microA/cm2. These electrophysiological results are comparable to reported values for other species. However, the resistance and potential obtained in this study were larger than those previously reported for the guinea pig. Tracheal diameter was decreased 15% by methacholine and was increased 43% by subsequent isoproterenol treatment. Isoproterenol caused a small but significant increase in Isc when this quantity was normalized to tracheal length rather than to the apparent surface area. In contrast, apical amiloride decreased Isc by 51% and did not change diameter. These data validate this implementation of cable analysis, demonstrate that sodium absorption is the predominant mechanism of active ion transport by guinea pig tracheal epithelium, and indicate that this tissue has little capacity for stimulated chloride secretion.

Muscarinic receptor subtypes mediating the mucosal response to neural stimulation of guinea pig ileum

1987 ◽  
Vol 253 (3) ◽  
pp. G323-G329 ◽  
Author(s):  
H. V. Carey ◽  
X. Y. Tien ◽  
L. J. Wallace ◽  
H. J. Cooke
Keyword(s):  
Guinea Pig ◽  
Muscarinic Receptors ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Neural Stimulation ◽  
Secretory Response ◽  
Receptor Subtypes ◽  
Guinea Pig Ileum ◽  
Stimulation Of

Muscarinic receptors involved in the secretory response evoked by electrical stimulation of submucosal neurons were investigated in muscle-stripped flat sheets of guinea pig ileum set up in flux chambers. Neural stimulation produced a biphasic increase in short-circuit current due to active chloride secretion. Atropine and 4-diphenylacetoxy-N-methylpiperadine methiodide (4-DAMP) (10(-7) M) were more potent inhibitors of the cholinergic phase of the response than was pirenzepine. Dose-dependent increases in base-line short-circuit current were evoked by carbachol and bethanechol; 4-hydroxy-2-butynyl trimethylammonium chloride (McN A343) produced a much smaller effect. Tetrodotoxin abolished the effects of McN A343 but did not alter the responses of carbachol and bethanechol. McN A343 significantly reduced the cholinergic phase of the neurally evoked response and caused a rightward shift of the carbachol dose-response curve. All muscarinic compounds inhibited [3H]quinuclidinyl benzilate binding to membranes from mucosal scrapings, with a rank order of potency of 4-DAMP greater than pirenzepine greater than McN A343 greater than carbachol greater than bethanechol. These results suggest that acetylcholine released from submucosal neurons mediates chloride secretion by interacting with muscarinic cholinergic receptors that display a high binding affinity for 4-DAMP. Activation of neural muscarinic receptors makes a relatively small contribution to the overall secretory response.

Aldosterone stimulates K secretion prior to onset of Na absorption in guinea pig distal colon

1994 ◽  
Vol 266 (2) ◽  
pp. C552-C558 ◽  
Author(s):  
D. R. Halm ◽  
S. T. Halm
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ussing Chambers ◽  
High Affinity Receptor ◽  
Additive Increase ◽  
K Secretion ◽  
Affinity Receptor

Distal colon from guinea pig was stimulated in vitro by aldosterone in Ussing chambers that allowed measurement of short-circuit current (Isc) and tissue conductance (Gt). The response to aldosterone was delayed by approximately 20 min and resulted in a negative Isc, consistent with K secretion. Approximately 1 h later the Isc began to increase and eventually became positive, consistent with subsequent stimulation of Na absorption. The Na-absorptive response could be inhibited by mucosal amiloride without altering the rate of K secretion. Similarly, K secretion could be inhibited by serosal bumetanide without altering Na absorption. In the presence of spironolactone, actinomycin D, or cycloheximide, aldosterone failed to stimulate both K secretion and Na absorption. A dose response to aldosterone provided an apparent Kd of 2.6 +/- 0.5 nM, consistent with a high-affinity receptor coupled to this secretory response. Stimulation by the K secretagogue epinephrine did not produce an additive increase in K secretion, suggesting that the same cell type responds to both aldosterone and epinephrine and that the protein induced by aldosterone was not one of the membrane proteins responsible for K secretion.

Mechanism of leukotriene D4 stimulation of Cl- secretion in rat distal colon in vitro

1993 ◽  
Vol 265 (3) ◽  
pp. G467-G473 ◽  
Author(s):  
C. S. Hyun ◽  
H. J. Binder
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Potential Difference ◽  
Maximal Response ◽  
Leukotriene D4 ◽  
Cl Secretion ◽  
Serotonergic Receptors ◽  
Mediators Of Inflammation

Lipoxygenase metabolites of arachidonic acid have been implicated as mediators of inflammation in inflammatory bowel disease (IBD). To assess their role in regulation of electrolyte transport, we investigated the effect of leukotriene D4 (LTD4) on ion transport across isolated rat colonic mucosa under voltage-clamp conditions. Serosal addition of LTD4 caused a dose-dependent rapid and transient increase in both short-circuit current (Isc) and potential difference, with maximal response at 1 microM. Pretreatment of the tissue with a specific LTD4 receptor antagonist (SKF-104353) inhibited these LTD4 effects. The effect of LTD4 on Isc and potential difference was also abolished by the absence of Cl- from both bathing solutions or by the presence of a Na(+)-K(+)-2Cl- cotransport inhibitor (bumetanide). A cyclooxygenase inhibitor (piroxicam) completely prevented the LTD4-induced increase in Isc. In addition, the effect of LTD4 on Isc was inhibited by either 5-hydroxytryptamine2 or 5-hydroxytryptamine3 antagonists (ketanserin and ICS-205-930, respectively). These results are consistent with a model in which LTD4 initially stimulates the synthesis from lamina propria cells of cyclooxygenase metabolites that induce electrogenic Cl- secretion, most likely via serotonergic receptors.

Stimulation of Cl- and HCO3- secretion by intramural cholinergic neurons in guinea pig antrum in vitro

1993 ◽  
Vol 264 (1) ◽  
pp. G118-G125 ◽  
Author(s):  
A. G. Suzuki ◽  
J. Kameyama ◽  
M. Tsukamoto ◽  
K. Kaneko ◽  
Y. Suzuki
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Cholinergic Neurons ◽  
Short Circuit Current ◽  
Muscarinic Agonist ◽  
Serosal Side ◽  
Ussing Chambers ◽  
Bethanechol Chloride ◽  
Stimulation Of

Regulation of Cl- and HCO3- secretion by intramural cholinergic neurons was investigated in guinea pig antrum in vitro. Sheet preparations composed of the mucosa and the submucosa were mounted between Ussing chambers and bathed with buffer-free solution on the luminal surface and with HCO3(-)-CO2 solution on the serosal side. Short-circuit current (Isc), unidirectional fluxes of 36Cl and 22Na, and the luminal alkalinization rate (JOHSL) were determined. Electrical stimulation of the preparations elicited increases in both JOHSL and Isc, which were inhibited by tetrodotoxin (TTX) and atropine. Physostigmine also evoked TTX- and atropine-sensitive increases in JOHSL and Isc. Similar increases in JOHSL and Isc were observed when the muscarinic agonist bethanechol chloride (BCh) was added to the serosal side. The responses to BCh were not affected by TTX. The BCh-induced increase in JOHSL was largely abolished by removal of HCO3- or Na+ and addition of ouabain (serosal side) but was neither sensitive to Cl- removal nor associated with 22Na secretion. The increase in Isc induced by BCh was associated with the increase in 36Cl secretion and was inhibited by removal of Cl- or Na+ and by addition of bumetanide or ouabain (both, serosal side). These results suggest that the submucosal cholinergic neurons are involved via muscarinic receptors in the stimulation of epithelial HCO3- and Cl- secretion. For both HCO3- and Cl-, the cellular and membrane mechanisms of secretion induced by muscarinic stimulation, although not entirely clear, appear to be different from those occurring under baseline conditions.

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