抄録
To investigate the role of a neuron playing in nervous system, it is important to determine the inputs and outputs of the neuron. So we tried a method to visualize both the input and the output pathways, maintaining neural functions intact. Rat cochlear nucleus (CN) was mainly used because it is easy to be approached and the neural connections are known anatomically. Visualization of outputs is established already by labeling cell bodies retrogradely with fluorescent dye injected in the output area. We confirmed availability of this method by injecting fluorescent beads or dye to inferior colliculus. We further visualized the input pathway to CN, auditory nerve fibers (ANFs), by injecting fluorescent dye DiI to cochlea. CN was sliced 2-4 days after the injection, and ANFs were identified by fluorescence to make contacts with neurons in CN. Functional synaptic contacts were confirmed by electorical stimulation to the fluorescing fiber with a glass micropipette. To investigate whether the identified single fiber was stimulated appropriately, we recorded responses with varying the stimulus intensity and the distance between the fiber and the microelectrode. These responses were also compared with that by stimulating the root of ANFs. A visualized fiber required weaker stimulation to evoke synaptic responses. Similar records were obtained in the medial nucleus of the trapezoid body (MNTB) after injection of DiI to CN. This method should be available in various parts of nervous systems, particularly useful by using multiple dyes of different fluorescence. [Jpn J Physiol 54 Suppl:S162 (2004)]
