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Title:Characterization and pharmacological analysis of electrical activity in the small intestine of fasting cat
Author(s):De Vos, Wayne Calvin
Doctoral Committee Chair(s):Prosser, C. Ladd
Department / Program:Molecular and Integrative Physiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Animal Physiology
Abstract:Electrical activity of smooth muscle of the small intestine in fasting cat was studied. 18 cats were each implanted with a set of 4-6 bipolar electrodes positioned at regular intervals along the distal half of the small intestine.
Results. During the fasting state all cats exhibited the "migrating spike complex" (MSC), an intense prolonged band of spike potentials not associated with slow waves, which appeared with great variability at approximately hourly intervals. The MSC migrated at a rate between 1-8 mm/sec, accelerating as it moves distally, and exhibits a refractory nature. The MSC was associated with an intense, prolonged contraction. Pharmacological analysis using IV infusion of neural receptor antagonists and/or agonists showed that nonspecific blockade of nicotinic or muscarinic receptors inhibited the propagation of the MSC. Infusion of agents specific for muscarinic-receptor subtypes showed that while blockade of m$\sb2$-receptors inhibited MSC propagation, blockade of m$\sb1$-receptors was followed by a significant, dose-dependent increase in MSC activity; stimulation of m$\sb1$-receptors blocked MSC propagation. Infusion of $\alpha$-adrenoceptor subtype specific agents showed that both $\alpha\sb1$- and $\alpha\sb2$-adrenoceptors are involved in the inhibitory control of MSC activity, while $\beta$-adrenoceptors do not appear to play a significant role in MSC activity. Also present during the fasting state in 9/18 cats was an activity characterized by a significant decrease in slow wave frequency and amplitude and a concomitant increase in spike potential duration and amplitude. These periods of "low frequency slow waves/giant spike bursts" (LFSW/GSB) lasted from 1-4 hours, were terminated by feeding, and were not associated with any apparent distress in the animal. Pharmacological analysis showed that periods of LFSW/GSB occurred significantly more often following infusion of an m$\sb1$-muscarinic receptor antagonist compared to saline; m$\sb1$-receptor stimulation or m$\sb2$-receptor blockade was followed by a transient inhibition of GSB activity. Blockade of nicotinic receptors inhibited LFSW/GSB activity, while $\alpha$-adrenoceptor blockade had no effect. Conclusion. The small intestine of the fasting cat exhibits at least two patterns of myoelectric activity, the MSC and the LFSW/GSB, which, unlike slow waves and spike bursts, require the integrity of the enteric nervous system for their expression and regulation. Neither activity has been reported from in vitro recordings.
Issue Date:1989
Rights Information:Copyright 1989 De Vos, Wayne Calvin
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9010845
OCLC Identifier:(UMI)AAI9010845

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