This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Gastroparesis, or delayed gastic emptying, occurs in approximately one third of patients with Type 2 diabetes mellitus (T2DM). While rarely fatal, it can cause serious nutritional complications that often require hospitalization. Vagal and autonomic neuropathy are commonly cited as the main causes of gastroparesis, however recent evidence suggests that interstitial cells of Cajal (ICC) may be involved. What is not known is how lesions in ICC networks cause gastric motor behavior to become abnormal. Two classes of ICC are found in the stomach and are responsible for 1) generating and conducting slow waves (ICC-MY) that produce antral peristalsis, and 2) acting as intermediaries between motor nerve ending and smooth muscle (ICC-IM). In this proposal we will investigate whether the pattern of deterioration of the ICC-MY network correlates to specific gastric dysrhythmias observed in T2DM. We will also investigate if damage or loss of intermediary ICC-IM reducers the effectiveness of motor transmission. A number of novel transgenic mice and advanced imaging technologies have recently become available that will allow a precise examination of changes in the structure of ICC networks to be correlated to motor dysfunctions. We will first observe and record motor abnormalities in the gastric antrum of mouse models of T2DM, then perform high resolution imaging in areas which showed abnormal motor activity and measure changes in the structure and density of ICC in the ICC-MY network. Ca2+ imaging and novel Ca2+ sensor expressing mice will allow us to explore changes that may be occurring at the cellular level of the ICC-MY network in T2DM mice. Using nerve stimulation we will examine which type of motor transmission is affected in T2DM mice, then using confocal and multi-photon confocal imaging, examine structural changes that occur between motor nerve fibers and ICC-IM that may indicate an unraveling of their normally close relationship. Using novel indicator dyes, we can directly observe the release and diffusion of the inhibitory neurotransmitter NO, and examine any dysfunctions. The most common recommendation for patients with T2DM is lifestyle changes involving diet and exercise. We will investigate whether these recommendations can prevent gastric motor abnormalities from occurring in diabetic mice, or whether gastric motor activity can be restored after damage has occurred in T2DM. Results from this study will determine if loss of ICC are responsible for gastroparesis.
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