NRG1 and Alzheimer disease: NRG1 heterozygous-mutant mice exhibited a decrease in the number of functional NMDA receptors in the forebrain,49 while treatment with NRG1 increased the number of spines in cultured hippocampal neurons.28 We measured the effects of NRG1 in both in vitro and in vivo experimental models of AD and investigated the underlying mechanisms of NRG1 function.