Correlation of morphology, electrophysiology and chemistry of neurons in the myenteric plexus of the guinea-pig distal colon

Lomax, Alan E.; Sharkey, Keith A.; Bertrand, Paul; Low, A M; Bornstein, Joel C.; Furness, John B.

doi:10.1016/s0165-1838(99)00008-9

Cited by 74 publications

(107 citation statements)

References 64 publications

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“…Interestingly, recent work in the colon has identified one class of neurons with the morphology of ascending interneurons, but which was also distensionsensitive (40 -42). Finally, the electrophysiological characteristics of colonic neurons (10,28,30,45) As might be expected, the peristaltic reflex differs between the ileum and the colon. For example, when the muscle is free to contract, a stationary distension of the gut wall causes a descending excitatory reflex in ileum (39) but an initial descending inhibitory reflex in the colon (12,15,38).…”

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confidence: 68%

Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon

Bian

Heffer

Gwynne

et al. 2004

American Journal of Physiology-Gastrointestinal and Liver Physi

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We examined specific receptor/transmitter combinations used at functionally identified synapses in ascending and descending reflex pathways of guinea pig distal colon. Excitatory (EJPs) or inhibitory junction potentials (IJPs) were recorded intracellularly from nicardipine-paralyzed circular smooth muscle in either the oral or anal recording chamber of a three-chambered organ bath, respectively. Blockade of synaptic transmission in the central chamber with a 0.25 mM Ca 2ϩ /12 mM Mg 2ϩ solution abolished EJPs evoked by distension applied either in the central or the far (anal) chamber. IJPs evoked by distension in the central or the far (oral) chamber were depressed to ϳ50% of control. Hexamethonium (nicotinic receptor antagonist, 200 M) in the central chamber reduced IJPs evoked by far or central distension to 50%, whereas EJPs evoked by far distension were abolished and EJPs evoked by central distension were reduced to 70% of control. Hexamethonium in the recording chambers reduced both IJPs and EJPs evoked by central distension to ϳ50%. EJPs in the ascending pathway were unaffected by blockade of muscarinic receptors in the central chamber or blockade of neurokinin 3 tachykinin receptors in this or the recording chamber. In the descending pathway, blockade of P2 receptors in the same chambers had only a minor effect on distension-evoked IJPs. Thus some intrinsic sensory neurons of guinea pig colon have long descending projections (Ͼ30 mm), but ascending projections of Ͻ15 mm. In contrast to the ileum, transmission between ascending or descending interneurons and from sensory neurons to descending interneurons is predominantly via nicotinic receptors; but transmission to inhibitory or excitatory motoneurons and from sensory neurons to ascending interneurons involves nicotinic and other unidentified receptors. enteric nervous system; electrophysiology; smooth muscle; enteric reflex THE COLON IS SPECIALIZED FOR the absorption of water and electrolytes and the storage and transport of material. The digestion and absorption of nutrients (such as those produced from bacterial fermentation) is of lesser overall importance. The intrinsic circuitry underlying colonic behavior may thus be quite different from that of the small intestine in which mixing and primary nutrient absorption are crucial functions. These differences are currently not well defined but are critical for interpretation of a vast range of currently available data.The guinea pig small intestine has been an excellent model for studying the circuitry of the enteric nervous system. It is in this system that the best data on projection patterns, chemical code, and electrophysiology have been gathered and correlated to characterize specific functional classes of neuron (8) and to reveal the nature of synaptic transmission at specific classes of synapses (7). The circuitry of the ileum, in particular, provides a template on which to design studies investigating the circuitry in the colon.Neuroanatomical studies (31, 33, 34) have revealed substantial similar...

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confidence: 68%

Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon

Bian

Heffer

Gwynne

et al. 2004

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…Obviously, therefore, they serve as the most suitable targets of promotility drugs. The reader is referred to other reviews for a complete discussion of these regulatory mechanisms (38,39,54,57,79). A brief summary of these regulatory mechanisms that is relevant to the design and development of promotility drugs follows.…”

Section: Selection Of Enteric Neurons And/or Circular Smooth Muscle Cmentioning

confidence: 99%

“…2A). The phase II and phase III contractions of the migrating motor complex in the fasting state result from spontaneous activity of ISANs (38,43). The trigger for the release of neurotransmitters to stimulate phase II and phase III contractions in the interdigestive state does not come from the ISNs.…”

Section: Selection Of Enteric Neurons And/or Circular Smooth Muscle Cmentioning

confidence: 99%

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Molecular, functional, and pharmacological targets for the development of gut promotility drugs

Sarna

2006

American Journal of Physiology-Gastrointestinal and Liver Physi

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. Molecular, functional, and pharmacological targets for the development of gut promotility drugs. Am J Physiol Gastrointest Liver Physiol 291: G545-G555, 2006. First published March 24, 2006 doi:10.1152/ajpgi.00122.2006.-The science of gastrointestinal motility has made phenomenal advances during the last fifty years. Yet, there is a paucity of effective promotility drugs to treat functional bowel disorders that affect 10 -29% of the U.S. population. A part of the reason for the lack of effective drugs is our limited understanding of the etiology of these diseases. In the absence of this information, mostly an ad hoc approach has been used to develop the currently available drugs, which are modestly effective or effective in only a subset of the patients with functional bowel disorders. This review discusses a grounds-up approach for development of the next generation of promotility drugs. The approach is based on our current understanding of 1) the different types of contractions that produce overall motility function of mixing and orderly net distal propulsion in major gut organs, 2) the regulatory mechanisms of these contractions, 3) which receptors and intracellular signaling molecules could be targeted to stimulate specific types of contractions to accelerate or retard transit, and 4) the strengths and limitations of animal models and experimental approaches that could screen potential promotility drugs for their efficacy in human gut propulsion in functional bowel disorders. smooth muscle; slow waves; enteric neurons; excitation-contraction coupling; peristaltic reflex; irritable bowel syndrome; prokinetic agents; gastroparesis; functional bowel disorders THE SCIENCE OF GASTROINTESTINAL MOTILITY has made phenomenal advances during the last fifty years. Our understanding of the individual regulatory mechanisms of motility function [excitation-contraction coupling in smooth muscle cells; enteric motor, sensory, and interneurons; enteric neurotransmitters, neuromodulators, and hormones; extrinsic neurons including spinal cord and central nervous system (CNS)] has matured (7, 18 -20, 26, 28, 39, 42, 53, 54, 57, 59, 60, 76, 78). However, significant gaps remain in our understanding of how and when the inputs from these mechanisms integrate to produce the normal mixing and propulsive motor functions of the gut; defects in these regulatory mechanisms result in motility dysfunction in diseases such as irritable bowel syndrome, inflammatory bowel disease, gastroparesis, and gastroesophageal reflux. Finally, our understanding of which receptors and intracellular signaling molecules in circular smooth muscle cells and enteric neurons could be targeted to normalize function in motility disorders is still rudimentary.Most currently available promotility drugs or those under development seem to have their origins in a known physiological or pharmacological effect or in their established role in a different system. For example, CCK receptor antagonists (loxiglumide and deloxyglumide) are thought to be potential promotil...

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“…Considerable heterogeneity has been reported in the morphological, neurochemical, and electrophysiological properties of neurons in the sympathetic ganglia [4,6]. Relationships between the shape and electrophysiological characteristics of neurons in the intestine of the guinea pig have been proposed [8], but there are also reports that dendritic complexity does not necessarily discriminate between functional types of autonomic neurons [6,7]. E.g., in the guinea pig pancreas, tonic cells were morphologically indistinguishable from phasic cells [7].…”

Section: Discussionmentioning

confidence: 99%

Ganglionic and non-ganglionic neurons in frog heart: do they differ?

Batulevičius

Skripkienė

Graužinytė

et al. 2017

PoA

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This study was designed to compare the morphology of neurons in relation to their distance from the major nerve trunks in the heart of the frog Rana temporaria. Seventy-nine intracardiac neurons were labelled intracellularly with fluorescent markers Lucifer Yellow CH and Alexa Fluor 568. The neurons located on the extensions of the vagus nerve were considered as ganglionic, while neurons spread loosely at further distance from these extensions were considered as non-ganglionic. The mean area of the soma in ganglionic neurons was about 25% larger than in non-ganglionic neurons. Ganglionic neurons had a higher soma area/nucleus area ratio than non-ganglionic neurons. Although both the total number and the total length of dendrite-like processes was similar between the two groups, ganglionic neurons had significantly fewer dendrite-like processes from the soma (1.5±0.3 vs. 3.9±1.0; P<0.05) and shorter total length of these processes from the soma (63±18 μm vs. 178±51 μm; P<0.05). In conclusion, ganglionic and non-ganglionic frog intracardiac neurons exhibit substantial morphological differences. We hypothesize that these differences may indicate different projections or variations in the number of their preganglionic inputs.

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Correlation of morphology, electrophysiology and chemistry of neurons in the myenteric plexus of the guinea-pig distal colon

Cited by 74 publications

References 64 publications

Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon

Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon

Molecular, functional, and pharmacological targets for the development of gut promotility drugs

Ganglionic and non-ganglionic neurons in frog heart: do they differ?

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