Long aboral projections of Dogiel type II, AH neurons within the myenteric plexus of the guinea pig small intestine

Brookes, Simon J.; Song, Zhenghua; Ramsay, G.A; Costa, M.

doi:10.1523/jneurosci.15-05-04013.1995

Cited by 88 publications

(81 citation statements)

References 31 publications

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“…The functional projections were asymmetrical, with long descending projections but no, or very short, ascending projections. Similar projections have been found for distension-sensitive Dogiel type II neurons (9) in the guinea pig ileum. Furthermore, the projections of extrinsic nerves would be predicted to be symmetrical, with equal lengths in the oral and anal direction, which suggests that the asymmetrical sensory pathways seen here are of intrinsic origin (i.e., an enteric neuron).…”

Section: Projection Lengths Of Neurons Within the Reflex Pathwayssupporting

confidence: 81%

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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Section: Projection Lengths Of Neurons Within the Reflex Pathwayssupporting

confidence: 81%

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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“…In the guinea pig, Brookes et al, (1991Brookes et al, ( , 1995 identified Calr-IR in "small" Dogiel type I neurons of both the myenteric and the submucosal plexus. However, our results and those of Mann et al (1997) indicated that in the rat, Calr-IRN are entirely Dogiel type II.…”

Section: Discussionmentioning

confidence: 99%

Morphology and distribution of nitric oxide synthase‐, neurokinin‐1 receptor‐, calretinin‐, calbindin‐, and neurofilament‐M‐immunoreactive neurons in the myenteric and submucosal plexuses of the rat small intestine

Sayegh

Ritter

2003

Anat. Rec.

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Characterization of the enteric neurons is vital for understanding their physiological role. We have used single and dual label fluorescence and peroxidase-based immunohistochemistry in myenteric and submucosal whole mounts from the rat small intestine to evaluate the morphology and distribution of enteric neurons immunoreactive for the following phenotypic antigens: neuronal nitric oxide synthase (NOS), neurokinin-1 receptor (NK-1R), calretinin (Calr), calbindin (Cal), and neurofilament-M (NF-M). NOS-immunoreactive neurons had Dogiel type I morphology, were abundant in the myenteric plexus compared to the submucosal plexus, and never coexpressed NK-1R immunoreactivity. NK-1R-and Calr-immunoreactive neurons had Dogiel type II morphology and were distributed comparably in both plexuses. NK-1R and Calr-immunoreactivity were coexpressed in many of the same neurons. Calbindin-immunoreactive neurons exhibited four distinct morphologies: small and large Dogiel type II neurons, Dogiel type I neurons, and small elongated neurons. These neurons were significantly fewer in number in the myenteric plexus compared to the submucosal plexus. Neurofilament-M-immunoreactive neurons had three morphologies, Dogiel type II neurons, small Dogiel type II neurons, and a less common subpopulation of small, elongated, multipolar neurons. These neurons were also fewer in number in the myenteric plexus compared to the submucosal plexus. The distribution of these phenotypic markers may assist future work that elucidates the functional activities of these enteric neurons such as control of intestinal motility and adaptation to the entry of gastric contents. Anat Rec Part A 271A: 209 -216, 2003.

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“…Second, while electrical stimulation evokes fast EPSPs mediated by nAChR in all S/uniaxonal neurons of the descending inhibitory pathway, many of these neurons also exhibit fast EPSPs mediated by either P2X or 5-HT 3 receptors [56,67,142]. Third, some sensory neurons have long anally projecting axons as well as circumferentially projecting axons [18], which complicates interpretation of data arising from pharmacological studies designed to isolate specific classes of synapses.…”

Section: Circuits Regulating Motility Reflexesmentioning

confidence: 99%

Synaptic Transmission at Functionally Identified Synapses in the Enteric Nervous System: Roles for Both Ionotropic and Metabotropic Receptors

Gwynne

Bornstein²

2007

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Digestion and absorption of nutrients and the secretion and reabsorption of fluid in the gastrointestinal tract are regulated by neurons of the enteric nervous system (ENS), the extensive peripheral nerve network contained within the intestinal wall. The ENS is an important physiological model for the study of neural networks since it is both complex and accessible. At least 20 different neurochemically and functionally distinct classes of enteric neurons have been identified in the guinea pig ileum. These neurons express a wide range of ionotropic and metabotropic receptors. Synaptic potentials mediated by ionotropic receptors such as the nicotinic acetylcholine receptor, P2X purinoceptors and 5-HT 3 receptors are seen in many enteric neurons. However, prominent synaptic potentials mediated by metabotropic receptors, like the P2Y 1 receptor and the NK 1 receptor, are also seen in these neurons. Studies of synaptic transmission between the different neuron classes within the enteric neural pathways have shown that both ionotropic and metabotropic synaptic potentials play major roles at distinct synapses within simple reflex pathways. However, there are still functional synapses at which no known transmitter or receptor has been identified. This review describes the identified roles for both ionotropic and metabotropic neurotransmission at functionally defined synapses within the guinea pig ileum ENS. It is concluded that metabotropic synaptic potentials act as primary transmitters at some synapses. It is suggested identification of the interactions between different synaptic potentials in the production of complex behaviours will require the use of well validated computer models of the enteric neural circuitry.

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Long aboral projections of Dogiel type II, AH neurons within the myenteric plexus of the guinea pig small intestine

Cited by 88 publications

References 31 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

Morphology and distribution of nitric oxide synthase‐, neurokinin‐1 receptor‐, calretinin‐, calbindin‐, and neurofilament‐M‐immunoreactive neurons in the myenteric and submucosal plexuses of the rat small intestine

Synaptic Transmission at Functionally Identified Synapses in the Enteric Nervous System: Roles for Both Ionotropic and Metabotropic Receptors

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