Objective: To characterize the effect of AMP-activated protein kinase (AMPK) on ATP-sensitive K+ (K-ATP) channels on substantia nigra compacta (SNC) dopamine neurons in slices of rat brain.

Background: AMPK is a master enzyme that regulates expression of K-ATP channels in pancreatic beta-cells and cardiac myocytes. K-ATP channels are also expressed in the SNC where they strongly inhibit neuronal activity. However, an AMPK K-ATP interaction in the SNC is unknown.

Methods: Patch-clamp recordings were used to investigate effects of AMPK on K-ATP currents evoke by diazoxide in SNC dopamine neurons in slices of rat midbrain.

Results: In the presence of the AMPK activator A769662, diazoxide current increased 372% when measured 60 min after starting whole-cell recording. But unexpectedly, we found that diazoxide currents also increased over time when pipettes did not contain A769662; although currents increased 200% over control, this was significantly less than the increase observed when A769662 was present (P < 0.001). Moreover, superfusing the slice with the AMPK blocking agent dorsomorphin significantly reduced diazoxide current to 38% of control, whether or not A769662 was present. Current-voltage plots showed that the increase in diazoxide current was associated with an increase in whole-cell conductance with a reversal potential near that expected for K+. 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 GABA-B agonist baclofen. Delaying the application of diazoxide after starting whole-cell recording correlated with augmentation of current, suggesting that the increase in diazoxide current was associated with dialysis of intracellular contents. Diazoxide produced small but significant slowing of spontaneous firing rate using loose-patch recordings. However, superfusion with A769662 significantly augmented the inhibitory effect of diazoxide on firing rate, suggesting that AMPK activation mimics the potentiation of ligand-gated K-ATP current that is seen with whole-cell recording.

Conclusions: We conclude that K-ATP channel function is augmented by AMPK, which is activated during the process of making whole-cell recordings. By potentiating the inhibitory effect of K-ATP channels in SNC neurons, AMPK could significantly alter many dopamine-dependent behaviors and conditions.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/amp-kinase-regulates-ligand-gated-k-atp-channels-in-substantia-nigra-dopamine-neurons/