TY - JOUR
T1 - Mechanisms of cannabinoid CB 2 receptor-mediated reduction of dopamine neuronal excitability in mouse ventral tegmental area
AU - Ma, Zegang
AU - Gao, Fenfei
AU - Larsen, Brett
AU - Gao, Ming
AU - Luo, Zhihua
AU - Chen, Dejie
AU - Ma, Xiaokuang
AU - Qiu, Shenfeng
AU - Zhou, Yu
AU - Xie, Junxia
AU - Xi, Zheng Xiong
AU - Wu, Jie
N1 - Publisher Copyright:
© 2019 The Authors
PY - 2019/4
Y1 - 2019/4
N2 - Background: We have recently reported that activation of cannabinoid type 2 receptors (CB 2 Rs)reduces dopamine (DA)neuron excitability in mouse ventral tegmental area (VTA). Here, we elucidate the underlying mechanisms. Methods: Patch-clamp recordings were performed in mouse VTA slices and dissociated single VTA DA neurons. Findings: Using cell-attached recording in VTA slices, bath-application of CB 2 R agonists (JWH133 or five other CB 2 R agonists)significantly reduced VTA DA neuron action potential (AP)firing rate. Under the patch-clamp whole-cell recording model, JWH133 (10 μM)mildly reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs)but not miniature inhibitory postsynaptic currents (mIPSCs). JWH133 also did not alter evoked EPSCs or IPSCs. In freshly dissociated VTA DA neurons, JWH133 reduced AP firing rate, delayed AP initiation and enhanced AP after-hyperpolarization. In voltage-clamp recordings, JWH133 (1 μM)enhanced M-type K + currents and this effect was absent in CB 2 −/− mice and abolished by co-administration of a selective CB 2 R antagonist (10 μM, AM630). CB 2 R-mediated inhibition in VTA DA neuron firing can be mimicked by M-current opener (10 μM retigabine)and blocked by M-current blocker (30 μM XE991). In addition, enhancement of neuronal cAMP by forskolin (10 μM)reduced M-current and increased DA neuron firing rate. Finally, pharmacological block of synaptic transmission by NBQX (10 μM), D-APV (50 μM)and picrotoxin (100 μM)in VTA slices failed to prevent CB 2 R-mediated inhibition, while intracellular infusion of guanosine 5'-O-2-thiodiphosphate (600 μM, GDP-β-S)through recording electrode to block postsynaptic G-protein function prevented JWH133-induced reduction in AP firing. Interpretation: Our results suggest that CB 2 Rs modulate VTA DA neuron excitability mainly through an intrinsic mechanism, including a CB 2 R-mediated reduction of intracellular cAMP, and in turn enhancement of M-type K + currents. Fund: This research was supported by the Barrow Neuroscience Foundation, the BNI-BMS Seed Fund, and CNSF (81771437).
AB - Background: We have recently reported that activation of cannabinoid type 2 receptors (CB 2 Rs)reduces dopamine (DA)neuron excitability in mouse ventral tegmental area (VTA). Here, we elucidate the underlying mechanisms. Methods: Patch-clamp recordings were performed in mouse VTA slices and dissociated single VTA DA neurons. Findings: Using cell-attached recording in VTA slices, bath-application of CB 2 R agonists (JWH133 or five other CB 2 R agonists)significantly reduced VTA DA neuron action potential (AP)firing rate. Under the patch-clamp whole-cell recording model, JWH133 (10 μM)mildly reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs)but not miniature inhibitory postsynaptic currents (mIPSCs). JWH133 also did not alter evoked EPSCs or IPSCs. In freshly dissociated VTA DA neurons, JWH133 reduced AP firing rate, delayed AP initiation and enhanced AP after-hyperpolarization. In voltage-clamp recordings, JWH133 (1 μM)enhanced M-type K + currents and this effect was absent in CB 2 −/− mice and abolished by co-administration of a selective CB 2 R antagonist (10 μM, AM630). CB 2 R-mediated inhibition in VTA DA neuron firing can be mimicked by M-current opener (10 μM retigabine)and blocked by M-current blocker (30 μM XE991). In addition, enhancement of neuronal cAMP by forskolin (10 μM)reduced M-current and increased DA neuron firing rate. Finally, pharmacological block of synaptic transmission by NBQX (10 μM), D-APV (50 μM)and picrotoxin (100 μM)in VTA slices failed to prevent CB 2 R-mediated inhibition, while intracellular infusion of guanosine 5'-O-2-thiodiphosphate (600 μM, GDP-β-S)through recording electrode to block postsynaptic G-protein function prevented JWH133-induced reduction in AP firing. Interpretation: Our results suggest that CB 2 Rs modulate VTA DA neuron excitability mainly through an intrinsic mechanism, including a CB 2 R-mediated reduction of intracellular cAMP, and in turn enhancement of M-type K + currents. Fund: This research was supported by the Barrow Neuroscience Foundation, the BNI-BMS Seed Fund, and CNSF (81771437).
KW - CB2 receptor
KW - Cannabinoid
KW - Dopamine neuron
KW - Ventral tegmental area
UR - https://www.scopus.com/pages/publications/85060346636
U2 - 10.1016/j.ebiom.2019.03.040
DO - 10.1016/j.ebiom.2019.03.040
M3 - 文章
C2 - 30952618
AN - SCOPUS:85060346636
SN - 2352-3964
VL - 42
SP - 225
EP - 237
JO - eBioMedicine
JF - eBioMedicine
ER -