Moreover, regarding the different molecular mechanisms of opioid effects on ventilation and antinociception, it has been established that the tropeine-mediated glycine receptor α3-5-HT1A–receptor complex initiates subcellular events that overcome fentanyl-induced respiratory depression but not fentanyl-induced analgesia (Manzke et al., 2011). Here, HTR1A is linked to Respiratory insufficiency due to muscle weakness.