Figure 3.
Schematic illustrating the canonical MOR signaling pathways via Gi/o-protein coupling. Gβγ can directly activate GIRK currents and directly inhibit voltage-gated Ca2+ currents. Gαi inhibits adenylyl cyclase, reducing the intracellular concentration of cyclic AMP. Reduced cAMP concentrations inhibit voltage-activated cation currents, such as HCN and can also indirectly influence the activity of numerous downstream effectors through inhibition of PKA. The predicted effects of these mechanisms on preBötC network function and the inspiratory rhythm depend on their somatic and/or synaptic sites of action. Predicted effects are color coded to the canonical pathways outlined above. GIRK, G-protein-activated inward rectifier K+ channels; MOR, mu-opioid receptor; preBOTc, preBӧtzinger complex.