AMP kinase regulates ligand-gated K-ATP channels in substantia nigra dopamine neurons.
AMP-activated protein kinase (AMPK) is a master enzyme that regulates ATP-sensitive K(+) (K-ATP) channels in pancreatic beta-cells and cardiac myocytes. We used patch pipettes to record currents and potentials to investigate effects of AMPK on K-ATP currents in substantia nigra compacta (SNC) dopamine neurons in slices of rat midbrain. When slices were superfused repeatedly with the K-ATP channel opener diazoxide, we were surprised to find that diazoxide currents gradually increased in magnitude, reaching 300% of the control value 60min after starting whole-cell recording. However, diazoxide current increased significantly more, to 472% of control, when recorded in the presence of the AMPK activator A769662. Moreover, superfusing the slice with the AMPK blocking agent dorsomorphin significantly reduced diazoxide current to 38% of control. Control experiments showed that outward currents evoked by the K-ATP channel opener NN-414 also increased over time, but not currents evoked by the GABAB agonist baclofen. Delaying the application of diazoxide after starting whole-cell recording correlated with augmentation of current. Loose-patch recording showed that diazoxide produced a 34% slowing of spontaneous firing rate that did not intensify with repeated applications of diazoxide. However, superfusion with A769662 significantly augmented the inhibitory effect of diazoxide on firing rate. We conclude that K-ATP channel function is augmented by AMPK, which is activated during the process of making whole-cell recordings. Our results suggest that AMPK and K-ATP interactions may play an important role in regulating dopamine neuronal excitability.
['Shen|Ke-Zhong|KZ|', 'Wu|Yan-Na|YN|', 'Munhall|Adam C|AC|', 'Johnson|Steven W|SW|']
D055372:AMP-Activated Protein Kinases D000200:Action Potentials D000818:Animals D001713:Biphenyl Compounds D019086:Bridged Bicyclo Compounds, Heterocyclic D002491:Central Nervous System Agents D003499:Cyclic S-Oxides D003981:Diazoxide D059290:Dopaminergic Neurons D004791:Enzyme Inhibitors D054086:KATP Channels D008297:Male D065842:Pars Compacta D018408:Patch-Clamp Techniques D011720:Pyrazoles D011743:Pyrimidines D011753:Pyrones D017207:Rats, Sprague-Dawley D013876:Thiophenes D046509:Tissue Culture Techniques
AMP kinase K-ATP substantia nigra diazoxide brain slice patch-clamp