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Title: The role of myenteric neurones in descending inhibition in the guinea-pig small intestin
Author: Leishman, D. J.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1991
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Gastrointestinal function is, in large part, controlled by the intrinsic nervous system of the gut; myenteric plexus neurones being especially influential in relation to control of motility. The function of a myenteric neurones is probably determined by the neuronal properties, accordingly the aim of the present study was a systematic investigation of the properties of myenteric neurones of the guinea-pig small intestine. Using microelectrodes filled with 0.5 m KCl and 0.5% Lucifer yellow (LY) intracellular recordings were made from these neurones. Permanent staining with the fluorescent dye, LY, makes possible the use of an indirect immunofluorescence technique to examine neurones of known electrophysiology and morphology. Highly selective antibodies to proenkephalin- and prodynorphin-derived peptides (Enk and Dyn, respectively) were used for immunofluorescence studies, opioid peptides being especially important in determining the motility pattern in the intestine. Neurones (381) were classified electrophysiologically into S- (314) and AH-neurones (66) for the exclusive properties of fast excitatory post synaptic potentials, in response to nerve tract stimulation, and a long-lasting after-hyperpolarization following soma action potentials, respectively. In addition, 1203 neurones were classified morphologically into 66% Dogiel Type I, 32% Type II and 2&37 Type III; type I neurones could be subdivided into 75% Type Ia and 25&37 Type Ib. The opioid peptide immunoreactivity (r) was examined in the majority of the electrophysiologically and morphologically classified neurones. Correlating morphology, electrophysiology and IR, important observations were made. All S-neurones had Type I or III morphology; AH-neurones being Type II. Opioid peptide immunoreactivity was restricted to S-neurones and Enk-IR was only found in Type I neurones. Many more neurones were Dyn-immunoreactive than were Enk-immunoreactive. These properties allowed a subdivision of myenteric neurones into 11 different groups; attempts were made to ascribe functional roles to these groups. Preparations were made in which descending nerve pathways in the gut were stimulated electrically or by distension and the time-course and latency of events evoked in neurones and circular smooth muscle cells compared. Using such comparisons neuronal correlates of inhibitory motor activity were identified. In conclusion, neurones likely to be inhibitory motor neurones were identified as, enkephalin-immunoreactive, S-neurones having Type Ia morphology.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available