Peripheral ablation of type III adenylyl cyclase induces hyperalgesia and eliminates KOR-mediated analgesia in mice
Wen-Wen Zhang, Hong Cao, Yang Li, Xian-Jun Fu, Yu-Qiu Zhang
Wen-Wen Zhang, Hong Cao, Yang Li, Xian-Jun Fu, Yu-Qiu Zhang
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Research Article Neuroscience

Peripheral ablation of type III adenylyl cyclase induces hyperalgesia and eliminates KOR-mediated analgesia in mice

Abstract

Ca2+/calmodulin-stimulated group I adenylyl cyclase (AC) isoforms AC1 and AC8 have been involved in nociceptive processing and morphine responses. However, whether AC3, another member of group I ACs, is involved in nociceptive transmission and regulates opioid receptor signaling remains elusive. Here, we report that conditional KO of AC3 (AC3 CKO) in L3 and L4 DRGs robustly facilitated the mouse nociceptive responses, decreased voltage-gated potassium (Kv) channel currents, and increased neuronal excitability. Furthermore, we report AC3 CKO eliminated the analgesic effect of κ-opioid receptor (KOR) agonist and its inhibition on Kv channel by classical Gαi/o signaling or nonclassical direct interaction of KOR and AC3 proteins. Interestingly, significantly upregulated AC1 level and cAMP concentration were detected in AC3-deficient DRGs. Inhibition of AC1 completely reversed cAMP upregulation, neuronal excitability enhancement, and nociceptive behavioral hypersensitivity in AC3-CKO mice. Our findings suggest a crucial role of peripheral AC3 in nociceptive modulation and KOR opioid analgesia.

Authors

Wen-Wen Zhang, Hong Cao, Yang Li, Xian-Jun Fu, Yu-Qiu Zhang

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Figure 3

Conditional KO of AC3 enhances the excitability of DRG neurons and decreases the Kv currents.

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Conditional KO of AC3 enhances the excitability of DRG neurons and decre...
(A) Image showing an isolated DRG neuron expressing EGFP with the tip of a pipette during patch clamp recording. Scale bar: 20 μm. (B and C) Depolarizing current pulse required to evoke an action potential (AP) in control (B) and AC3-CKO (C) DRG neurons. (D–F) AC3 CKO reduced the rheobase required to evoke AP (D), increased the RMP (more positive; E) and had no difference in the membrane capacitance (F) of recorded neurons. *P < 0.05, ***P < 0.001; 2-tailed Student’s t test; n = 20 Ctrl and 22 CKO (cells). (G) Examples of the AP traces from control and AC3-CKO neurons. (H) AC3 CKO increased the number of APs evoked by current injection. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001; 2-way RM ANOVA followed by Bonferroni’s test; n = 20 Ctrl and 22 CKO (cells). (I and J) Pharmacologically separated IA (I) and IK (J) in control and AC3-CKO DRG neurons under different holding voltage. AC3 deficiency robustly attenuated IA (I) and IK (J) densities of DRG neurons. ***P < 0.001; 2-way RM ANOVA followed by Bonferroni’s test; n = 8–11 (cells). (K–M) AC3 CKO did not shift the steady-state activation curve and half-activation voltage of Kv channels (K and M), but it left-shifted the steady-state inactivation curve of Kv channels toward hyperpolarizing direction and decreased half-inactivation voltage (more negative) in DRG neurons (L and M). **P < 0.01; 2-tailed Student’s t test; n = 14–16 (cells).