Physiology - Theses

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End date: 2009 × Start date: 2001 × Subject: enteric nervous system ×

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    Mathematical and computer modelling of the enteric nervous system
    Thomas, Evan Alexander ( 2001)
    The enteric nervous system (ENS) runs within the intestinal wall and is responsible for initiating and enacting several reflexes and motor patterns, including peristalsis and the complex interdigestive motor programs, known as migrating motor complexes (MMCs). The ENS consists of several neuron types including intrinsic sensory neurons, interneurons and motor neurons. A great deal is known about the anatomy, pharmacology and electrophysiology of the ENS, yet there is almost no understanding of how enteric neural circuits perform the functions that they do and how they switch from one function to another. The ENS contains intrinsic sensory neurons (ISNs) that connect to every neuron type in the ENS, including making recurrent connections amongst themselves. Thus, they are likely to play a key role, not just in sensory transduction, but in coordination of reflexes and motor patterns. This thesis has explored how these functions are performed by developing and analysing mathematical and computer models of the network of ISNs. (For complete abstract open document)
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    Enteric serotonin interneurons: connections and role in intestinal movement
    NEAL, KATHLEEN BRONWYN ( 2008)
    5-HT powerfully affects gastrointestinal function. However, the study of these effects is complicated because 5-HT from both mucosa and a subset of enteric neurons acts on multiple receptor subtypes in enteric tissues. The role of neural 5-HT has been difficult to isolate with current techniques. This thesis aimed to elucidate the role of 5-HT neurons in motility using anatomical and functional methods. In Chapter 2, confocal microscopy was used to examine over 95% of myenteric neurons in guinea pig jejunum, categorized neurochemically, to identify neurons that received anatomically-defined input from 5-HT interneurons. The data showed that cholinergic secretomotor neurons were strongly targeted by 5-HT interneurons. In another key finding, excitatory motor neurons were surrounded by 5-HT terminals; this could provide an anatomical substrate for the descending excitation reflex. Subgroups of ascending interneurons and neurons with immunoreactivity for NOS, were also targeted by 5-HT interneurons. Thus, subtypes of these neurons might act in separate reflex pathways. Despite strong physiological evidence for 5-HT inputs to AH/Dogiel type II neurons, few contacts were identified. In Chapter 3, the confocal microscopy survey was extended to the three other interneuron classes (VIP/NOS and SOM descending interneurons; calretinin ascending interneurons) of guinea pig small intestine. A high degree of convergence between the otherwise polarized ascending and descending interneuron pathways was identified.