Evidences for a new cation channel in the brain mitochondrial inner membrane

Previous studies and our works have indicated several cation channels in the rat brain mitochondrial inner membrane. In this work, we report the single-channel characterization of a cation channel from the rat brain mitochondrial inner membrane incorporated into a planar lipid bilayer. After removing and homogenizing the adult rat brain, its supernatant was centrifuged in MSE-digitonin, H2O and Na2CO3, separately. Then, mitochondrial inner membrane vesicles were prepared in MSE solution. L-α- Phosphatidylcholine (for preparing membrane lipid bilayer) was extracted from fresh egg yolk. Bilayer lipid membranes were formed in a 150 μm diameter hole. All single channel recordings were filtered at 1 kHz and stored at a sampling rate of 10 kHz for offline analysis by PClamp10. Statistical analysis was performed based on Markov noise free single channel analysis. The channel conductance was 93 pS in 200 mM KCl cis/50 mM KCl trans. The channel open probability appeared voltage-independent at -50 to +40 mV. The main characteristic of channel gating was its marked bursting behavior. Adding 10 mM 4-aminopyridine (4-AP) at positive and negative potentials inhibited the channel activities. These results demonstrate that a new cation channel, present in the brain mitochondrial inner membrane, displays different kinetics and biophysical properties than those classically described for brain mitochondria.