Central vagal stimulation evokes gastric volume changes in mice: a novel technique using a miniaturized barostat

We have developed a novel technique to measure gastric volume in vivo in mice; this will be invaluable for revealing gastric alterations in genetically modified mice models, thus expanding our understanding of the mechanisms underlying functional disorders. Experimental data on gastric tone currently available has focused on rats using isovolumetric techniques to measure pressure changes, whereas clinical studies use barostatic techniques to measure volume changes. For better translational approaches, we assessed the feasibility of using a miniaturized barostat to measure gastric volume changes in urethane-anaesthetized and unanaesthetized-decerebrate mice. Additionally, we assessed whether central vagal stimulation alters gastric volume in urethane-anaesthetized mice. Nitric oxide donor sodium nitroprusside (1mg kg-1 i.p.) increased gastric volume (+134 +/- 20 microL), whereas the cholinergic agonist carbachol (3 microg kg-1 i.p.) decreased gastric volume (-153 +/- 20 microL). Similar responses were obtained in urethane-anaesthetized and unanaesthetized-decerebrate animals. Microinjection of L-glutamate (25 nmol) into dorsal motor nucleus of the vagus (DMV) altered gastric volume; microinjection into rostral DMV led to gastric contraction (-83 +/- 18 microL) while stimulation of caudal DMV resulted in gastric relaxation (+95 +/- 16 microL). This reveals a functional organization of DMV in mice. This study validates barostatic techniques for application to mice. An understanding of gastric contractility and tone is clinically relevant as impaired gastric accommodation reflex may be an underlying cause of functional dyspepsia.