Effects of brain-gut related peptides on cAMP levels in myenteric ganglia of guinea-pig small intestine

doi:10.1016/0922-4106(92)90034-S

European Journal of Pharmacology: Molecular Pharmacology

Volume 225, Issue 1, 14 January 1992, Pages 21-27

https://doi.org/10.1016/0922-4106(92)90034-S Get rights and content

Abstract

This study was designed to test the hypothesis that stimulation of adenylate cyclase and elevation of cAMP is involved in the signal transduction process for substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, cholecystokinin or gastrin releasing peptide in myenteric ganglia. Enzymatically dissociated ganglia from the myenteric plexus of the guinea-pig small intestine were used to study changes in levels of cAMP in response to application of the brain-gut peptides in the presence and absence of forskolin. Application of substance P and calcitonin gene-related peptide were found to increase intraganglionic cAMP in a dose-dependent fashion when a phosphodiesterase inhibitor was present. The ED₅₀ values for substance P and calcitonin gene-related peptide were 5 μM and 0.75 μM, respectively. The presence of forskolin in the incubation medium resulted in significant upward shifts of the dose-response curves for both peptides. Neither vasoactive intestinal peptide. cholecystokinin nor gastrin releasing peptide stimulated increases in intraganglionic cAMP under the same experimental conditions used for substance P and calcitonin gene-related peptide.

References (17)

C.R. Albrightson et al.
Psoralens increase the concentration of cyclic AMP in human cells in vitro
J. Invest. Dermatol.
(1985)
P.R. Nemeth et al.
Effects of cholecystokinin caerulein and pentagastrin on electrical behavior of myenteric neurons
Eur. J. Pharmacol.
(1985)
J.M. Palmer et al.
Calcitonin gene-related peptide excites myenteric neurons
Eur. J. Pharmacol.
(1986)
Y. Xia et al.
Determination of levels of cyclic AMP in myenteric ganglia of the guinea-pig small intestine
Eur. J. Pharmacol.
(1991)
D.H. Zafirov et al.
Bombesin, gastrin releasing peptide and vasoactive intestinal peptide excite myenteric neurons
Eur. J. Pharmacol.
(1985)
L.V. Baidan et al.
Effects of substance P and calcitonin gene-related peptide on levels of cAMP in enzymatically dissociated ganglia from guinea-pig small intestine
Gastroenterology
(1991)
F. Christofi et al.
Release of endogenous adenosine modulates the synaptic and electrical behavior of myenteric of the guinea pig distal ileum
J. Gastrointest. Mol.
(1989)
I.L. Gibbibs et al.
Co-localization of calcitonin gene-related peptide-like immunoreactivity with substance P in cutaneous, vascular and visceral sensory neurons of guinea pigs
Neurosci. Lett.
(1985)

There are more references available in the full text version of this article.

Cited by (26)

Cyclic AMP signaling contributes to neural plasticity and hyperexcitability in AH sensory neurons following intestinal Trichinella spiralis-induced inflammation
2007, International Journal for Parasitology
Trichinella spiralis infection causes hyperexcitability in enteric after-hyperpolarising (AH) sensory neurons that is mimicked by neural, immune or inflammatory mediators known to stimulate adenylyl cyclase (AC)/cyclic 3′,5′-adenosine monophosphate (cAMP) signaling. The hypothesis was tested that ongoing modulation and sustained amplification in the AC/cAMP/phosphorylated cAMP related element binding protrein (pCREB) signaling pathway contributes to hyperexcitability and neuronal plasticity in gut sensory neurons after nematode infection. Electrophysiological, immunological, molecular biological or immunochemical studies were done in T. spiralis-infected guinea-pigs (8000 larvae or saline) after acute-inflammation (7 days) or 35 days p.i., after intestinal clearance. Acute-inflammation caused AH-cell hyperexcitability and elevated mucosal and neural tissue levels of myeloperoxidase, mast cell tryptase, prostaglandin E2, leukotrine B4, lipid peroxidation, nitric oxide and gelatinase; lower level inflammation persisted 35 days p.i. Acute exposure to blockers of AC, histamine, cyclooxygenase or leukotriene pathways suppressed AH-cell hyperexcitability in a reversible manner. Basal cAMP responses or those evoked by forskolin (FSK), Ro-20-1724, histamine or substance P in isolated myenteric ganglia were augmented after T. spiralis infection; up-regulation also occurred in AC expression and AC-immunoreactivity in calbindin (AH) neurons. The cAMP-dependent slow excitatory synaptic transmission-like responses to histamine (mast cell mediator) or substance P (neurotransmitter) acting via G-protein coupled receptors (GPCR) in AH neurons were augmented by up to 2.5-fold after T. spiralis infection. FSK, histamine, substance P or T. spiralis acute infection caused a 5- to 30-fold increase in cAMP-dependent nuclear CREB phosphorylation in isolated ganglia or calbindin (AH) neurons. AC and CREB phosphorylation remained elevated 35 days p.i.. Ongoing immune activation, AC up-regulation, enhanced phosphodiesterase IV activity and facilitation of the GPCR-AC/cAMP/pCREB signaling pathway contributes to T. spiralis-induced neuronal plasticity and AH-cell hyperexcitability. This may be relevant in gut nematode infections and inflammatory bowel diseases, and is a potential therapeutic target.
Slow excitatory post-synaptic potentials in myenteric AH neurons of the guinea-pig ileum are reduced by the 5-hydroxytrytamine<inf>7</inf> receptor antagonist SB 269970
2005, Neuroscience
Serotonin (5-HT) is a key modulator of neuronal excitability in the central and peripheral nervous system. In the enteric nervous system, 5-HT causes a slow depolarization in the intrinsic sensory neurons, but the receptor responsible for this has not been correlated with known gene products. The aim of this study was to determine whether the newly characterized 5-HT₇ receptor may participate in the 5-HT-mediated depolarization of, and synaptic transmission to, the intrinsic sensory neurons of the guinea-pig ileum.
Intracellular electrophysiological recordings were made from intrinsic sensory neurons identified as myenteric AH neurons from guinea-pig ileum. 5-HT (5μM) applied to the cell body evoked both a fast depolarization (5-HT₃ mediated) and/or a slow depolarization (5-HT_1P-like). The 5-HT_1/5/7 receptor agonist 5-carboxamidotryptamine (5-CT) (5μM) evoked only a slow depolarization. When the fast depolarization evoked by 5-HT was blocked with granisetron (1μM, 5-HT₃ receptor antagonist), only a slow depolarization remained; this was abolished by the 5-HT₇ receptor antagonist SB 269970 (1μM, control: 14±2 mV, granisetron+SB 269970: −1±2 mV). The slow depolarization evoked by 5-CT was also significantly reduced by SB 269970 (control: 14±1 mV, SB 269970: 5±2 mV) suggesting a 5-HT₇ receptor was activated by exogenous application of 5-CT and 5-HT. Slow excitatory postsynaptic potentials evoked by stimulating descending neural pathways (containing serotonergic fibers) were reduced by SB 269970 (control: 8±3 mV, SB 269970: 3±1 mV). However, SB 269970 had no effect on slow excitatory postsynaptic potentials evoked by stimulation of circumferential (tachykinergic) pathways (control: 7±1 mV, SB 269970: 6±1 mV).
These data are consistent with the presence on enteric AH neurons of functional 5-HT₇ receptors that participate in slow synaptic transmission.
Inhibitory cotransmission or after-hyperpolarizing potentials can regulate firing in recurrent networks with excitatory metabotropic transmission
2003, Neuroscience
Recurrent networks of neurons communicating via excitatory connections are common in the nervous system. In the absence of mechanisms to control firing (collectively termed negative feedback), these networks are likely to be bistable and unable to meaningfully encode input signals. In most recurrent circuits, negative feedback is provided by a specialized subpopulation of interneurons, but such neurons are absent from some systems, which therefore require other forms of negative feedback. One such circuit is found within the enteric nervous system of the intestine, where AH/Dogiel type II neurons are interconnected via excitatory synapses acting through metabotropic receptors to produce slow excitatory postsynaptic potentials (slow EPSPs). Negative feedback in this recurrent network may come from either inhibitory postsynaptic potentials arising from the terminals that produce slow EPSPs or from the after hyperpolarizing potentials (AHPs) characteristic of these neurons. We have examined these possibilities using mathematical analysis, based on the Wilson-Cowan model, and computer simulations. Analysis of steady states showed that, under appropriate conditions, both types of negative feedback can provide robust regulation of firing allowing the networks to encode input signals. Numerical simulations were performed using large, anatomically realistic networks with realistic models for metabotropic transmission and suppression of the AHP. In the presence of constant exogenous input, parameters controlling aspects of synaptic events were varied, confirming the analytical results for static stimuli. The simulated networks also responded to time varying inputs in a manner consistent with known physiology. In addition, simulation revealed that neurons in networks with inhibitory contransmission fired in erratic bursts, a phenomenon observed in neurons in unparalysed tissue. Thus, either inhibitory contransmission or AHPs, or both, can allow recurrent networks of AH/Dogiel type II neurons to encode ongoing inputs in a biologically useful way. These neurons appear to be intrinsic primary afferent neurons (IPANs), which implies that the IPANs in a region act in a coordinated fashion.
FlCRhR/cyclic AMP signaling in myenteric ganglia and calbindin-D<inf>28</inf> intrinsic primary afferent neurons involves adenylyl cyclases I, III and IV
1999, Brain Research
The aims of this study were to improve insight into cAMP signaling in myenteric neurons and glia and identify the adenylyl cyclase (AC) isoforms expressed in myenteric ganglia of the guinea-pig small intestine. An increase in the intracellular cAMP levels was measured indirectly by an increase in the 520 nm/580 nm fluorescence emission ratio of the protein kinase A fluorosensor FlCRhR. Forskolin or pituitary adenylyl cyclase activating peptide caused an increase in cAMP levels in cell somas and neurites and elicited a slow EPSP-like response in myenteric AH/Type 2 neurons, whereas the inactive form of forskolin was without these effects. Glia displayed similar cAMP responses. Immunoblot analysis showed that AC I, III and IV were present in myenteric ganglia, with AC I being detected as two bands of 160 kDa and 185 kDa, AC III as two bands near 220 kDa, and AC IV as two bands of greater than 220 kDa. Pretreatment with N-ethylmaleimide and N-glycosidase F revealed an AC IV band at 115 kDa. Preabsorption with specific blocking peptides prevented detection of AC I or AC IV immunoreactive proteins. In ganglia which expressed strong AC IV immunoreactivity, no immunoreactive bands were detected for AC II, AC V/VI, AC VII or AC VIII. The amount of AC isoforms expressed in myenteric ganglia followed the order of AC IV≫III>I. Immunofluorescent labeling studies revealed that AC I, AC III and AC IV were variably expressed in myenteric neurons and glia of the duodenum, jejunum and ileum. In the guinea-pig ileum, AC I, III and IV immunoreactivities were respectively present in 26%, 58% and 89% of calbindin-D₂₈—colabeled myenteric neurons. These findings suggest that (1) AC I, AC III and AC IV variably contribute to cAMP signaling in myenteric ganglia, (2) AC I, AC III and AC IV may be differentially expressed in distinct subsets of calbindin-D₂₈ neurons which may represent intrinsic primary afferent myenteric neurons. Our study also provides direct evidence for activation of cAMP-dependent protein kinase.
Intrinsic primary afferent neurons of the intestine
1998, Progress in Neurobiology
After a long period of inconclusive observations, the intrinsic primary afferent neurons of the intestine have been identified. The intestine is thus equipped with two groups of afferent neurons, those with cell bodies in cranial and dorsal root ganglia, and these recently identified afferent neurons with cell bodies in the wall of the intestine.
The first, tentative, identification of intrinsic primary afferent neurons was by their morphology, which is type II in the terminology of Dogiel. These are multipolar neurons, with some axons that project to other nerve cells in the intestine and other axons that project to the mucosa.
Definitive identification came only recently when action potentials were recorded intracellularly from Dogiel type II neurons in response to chemicals applied to the lumenal surface of the intestine and in response to tension in the muscle. These action potentials persisted after all synaptic transmission was blocked, proving the Dogiel type II neurons to be primary afferent neurons.
Less direct evidence indicates that intrinsic primary afferent neurons that respond to mechanical stimulation of the mucosal lining are also Dogiel type II neurons.
Electrophysiologically, the Dogiel type II neurons are referred to as AH neurons. They exhibit broad action potentials that are followed by early and late afterhyperpolarizing potentials.
The intrinsic primary afferent neurons connect with each other at synapses where they transmit via slow excitatory postsynaptic potentials, that last for tens of seconds. Thus the intrinsic primary afferent neurons form self-reinforcing networks.
The slow excitatory postsynaptic potentials counteract the late afterhyperpolarizing potentials, thereby increasing the period during which the cells can fire action potentials at high rates.
Intrinsic primary afferent neurons transmit to second order neurons (interneurons and motor neurons) via both slow and fast excitatory postsynaptic potentials.
Excitation of the intrinsic primary afferent neurons by lumenal chemicals or mechanical stimulation of the mucosa appears to be indirect, via the release of active compounds from endocrine cells in the epithelium. Stretch-induced activation of the intrinsic primary afferent neurons is at least partly dependent on tension generation in smooth muscle, that is itself sensitive to stretch.
The intrinsic primary afferent neurons of the intestine are the only vertebrate primary afferent neurons so far identified with cell bodies in a peripheral organ. They are multipolar and receive synapses on their cell bodies, unlike cranial and spinal primary afferent neurons. They communicate with each other via slow excitatory synaptic potentials in self reinforcing networks and with interneurons and motor neurons via both fast and slow EPSPs.
Suppression of cAMP formation by adenosine in myenteric ganglia from guinea-pig small intestine
1997, European Journal of Pharmacology
Effects of the adenosine receptor agonist 2-chloro-N⁶-cyclopentyl-adenosine (CCPA) on stimulation of cAMP formation by histamine, 5-hydroxytryptamine, substance P and forskolin were determined for enzymatically dissociated ganglia from the myenteric plexus of guinea-pig small intestine. Each of the 4 substances stimulated cAMP production. CCPA blocked the stimulation of cAMP by histamine, but not by 5-hydroxytryptamine or substance P. CCPA marginally suppressed stimulation by forskolin. CCPA alone suppressed basal levels of cAMP. The adenosine receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT) reversed the inhibitory action of CCPA on stimulation of cAMP formation by histamine. Exposure to adenosine deaminase or CPT increased cAMP in the ganglia. The results are consistent with a hypothesis that stimulation of adenylate cyclase and elevation of intraneuronal cAMP in enteric neurons are steps in the signal transduction cascade for the excitatory actions of 5-hydroxytryptamine, substance P and histamine. They are consistent also with an original hypothesis from electrophysiologic studies which states that stimulation of adenosine A₁ receptors suppresses cAMP formation and thereby slow synaptic excitation in response to histamine, but not to 5-hydroxytryptamine or substance P. The results support evidence from intracellular microelectrode studies which suggested that endogenous adenosine accumulates to levels sufficient for tonic suppression of cAMP formation in myenteric ganglia in vitro.

View all citing articles on Scopus

View full text

Effects of brain-gut related peptides on cAMP levels in myenteric ganglia of guinea-pig small intestine

Abstract

J. Invest. Dermatol.

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Effects of substance P and calcitonin gene-related peptide on levels of cAMP in enzymatically dissociated ganglia from guinea-pig small intestine

Gastroenterology

Release of endogenous adenosine modulates the synaptic and electrical behavior of myenteric of the guinea pig distal ileum

J. Gastrointest. Mol.

Co-localization of calcitonin gene-related peptide-like immunoreactivity with substance P in cutaneous, vascular and visceral sensory neurons of guinea pigs

Neurosci. Lett.