Researchers at NIH have generated transgenic mice in which the M3 muscarinic receptor is overexpressed in pancreatic beta cells. This was done by placing the receptor gene under the control of the 650 bp rat insulin promoter II (RIP II). The resulting mice show a pronounced increase in glucose tolerance and enhanced plasma insulin levels. Strikingly, these mutant mice were resistant to diet-induced glucose intolerance and hyperglycemia.