Prolonged activation of mitochondrial conductances during synaptic transmission

Although ion channels have been detected in mitochondria, scientists have n ot been able to record ion transport in mitochondria of intact cells. A Var iation of the patch clamp technique was used to record ion channel activity from intracellular organelles in the presynaptic terminal of the squid. El ectron microscopy indicated that mitochondria are numerous in this terminal and are the only organelles compatible with the tips of the pipettes. Befo re synaptic stimulation, channel activity was infrequent and its conductanc e was small, although Large conductances (similar to 0.5 to 2.5 nanosiemens ) could be detected occasionally. During a train of action potentials, the conductance of the mitochondrial membrane increased up to 60-fold, The cond uctance increased after a delay of several hundred milliseconds and continu ed to increase after stimulation had stopped. Recovery occurred over tens o f seconds.