TACR1 and Respiratory insufficiency due to muscle weakness: These studies also report the loss of respiratory depression by both flupirtine and DAMGO, as well as a reduced augmentative effect by the positive neuromodulator GR73632 (an NK-1 receptor agonist) in homozygous Girk2 KO mice, compared to WT controls (Montandon et al., 2016a, b).