A thick band of microtubules in certain neurons in the retina help provide energy required for visual processing, researchers now believe.
The discovery of the pathways for mitochondria is published in The Journal of General Physiology.
The retina contains specialised neurons called bipolar cells that transmit information from light-sensitive photoreceptor cells to ganglion neurons, which send information to the brain for interpretation as images.
Unlike most neurons, bipolar cells are continuously active and so require a constant supply of energy. The discovery could explain how they do it.
researchers from the National Heart, Lung, and Blood Institute and Yale University used cutting-edge 3D microscopy to examine the subcellular architecture in retinal bipolar cells of live goldfish.
Unexpectedly, the team discovered a thick band of microtubules, a component of the cell’s cytoskeleton, that extended from the axon of the neuron into the synaptic terminal and then looped around the interior periphery of the terminal.
The microtubule band appeared to associate with mitochondria – organelles known for providing energy to cells – in the synaptic terminal. When the researchers administered drugs to inhibit the movement of certain “motor” proteins that transport mitochondria and other cargo within the cell by traveling along microtubules, the mitochondria accumulated in the axon of the neuron and never made it to the synaptic terminal.