Effect of electrical stimulation of the vagus nerve on colonic contractions and colonic neuron/ICC calcium activity, in ex vivo preparations lacking the targets of vagal afferent input.
Study Purpose: This study was conducted to determine the effects of vagus nerve stimulation of colon on colonic motility.
Data Collection: Calcium imaging of cholinergic and nitrergic neurons as well as ICC, and tension recording of proximal middle and distal colon.
Primary Conclusion: To evaluate the effect of stimulating the efferent component of the right vagal nerve trunk on colonic motility in the mouse, we measured colonic migrating motor complexes by tension recording and activity of cholinergic and nitrergic neurons of the colonic myenteric plexus and interstitial cells of Cajal (ICC) of the submucosal plexus by calcium imaging, in an ex vivo preparation of the colon also containing the vagus nerves. We found no change in contractile activity before, during, or after VNS at multiple frequencies and durations. Similarly, we did not detect any differences in calcium responses in response to VNS in this preparation.
Experimental Design: Adult mice of each sex were killed by isoflurane inhalation, and cervical dislocation, in accordance with the requirements of the Animal Ethics Committee at the University of Nevada, Reno. A ventral midline incision was made, and the entire colon was removed and placed in a Sylgard-lined dish that was perfused with Krebs-Ringer buffer solution. Functional imaging was performed on a Nikon Eclipse FN1 upright fluorescence microscope using Nikon Plan Fluor 20x lens. Image sequences were captured using a Photometrics Prime 95B sCMOS camera and captured on a Windows-based PC using Nikon NIS Elements 4.1. Image sequences were recorded at 25 frames per second. For tension, the colon is then drawn over a 1.5-mm diameter fire-polished capillary tube whose length exceeds that of the colon. An artificial pellet is mounted to the capillary glass and the colon is positioned with the pellet in the middle. Resting tension is initially set at 8 mN and monitored using an MP100 interface and recorded on a PC running Acqknowledge software 3.2.6 (Biopac Systems). A suction electrode connected to a 10ml syringe and tubing is then placed over the right vagus nerve trunk and upward pressure is applied to suck in the nerve. Stimulation is then performed with a variety of pulse durations and frequencies.
Completeness: This dataset is a part of a larger study " Comprehensive Structural and Functional Mapping of Mammalian Colonic Nervous System"
Subjects & Samples: Male (n=12) and female (n=9) adult transgenic and wild-type mice were used in this study.
Primary vs derivative data: The primary data is organized in folders by subject ID. Sample subfolders include either calcium imaging videos or, for a subset of samples, tension recordings as .scq files. The. avi microscope movies are of calcium transient and movement responses of the middle colon of ICC (ICC-GCaMP), cholinergic neurons (ChAT-GCaMP6f) and nitrergic neurons (nNOS-GCaMP6f). There is no derivative data folder.
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