Figure 1
Brief overview of major features that make the Mauthner cell an interesting experimental system to elucidate the differential actions of anaesthetics. (a) Multisensory integration and motor output: Sketch of a teleost fish with central nervous system (grey), the right one of its two Mauthner neurons (orange spot) in the hindbrain, sensory input to the Mauthner neuron (red) and its motor output (blue). When input is suprathreshold, one of the two Mauthner neurons fires one action potential and this will cause body bending by activating trunk muscles on the contralateral side. (b–d) The Mauthner neuron is an identified neuron that is easy to find and to record from. Though buried deeply in the hindbrain, the Mauthner cell soma can be found for in vivo recording on the basis of an all-or-none field potential that emerges from an associated structure in direct vicinity, the axon cap, when the Mauthner axon is activated by stimuli applied to the spinal cord. (b) To illustrate this important feature, the known increase of this field potential during a direct approach from the medullary surface to the centre of the axon cap is shown for goldfish. D indicates the distance between the recording electrode and the centre of the axon cap at respective measuring position. (c) A map of the field potential amplitude at the depth of the goldfish Mauthner cell – about 1.2 mm under the surface of the medulla, with distance from major medullary landmarks (4th ventricle and midline) indicated (208 sampling points; right hemisphere; distance between points between 25 and 100 µm depending on steepness of change in field potential). (d) At the field potential maximum, advancing the electrode slightly further will allow recording from the Mauthner neuron. Its identity can be confirmed by several unique characteristics of its action potential, such as its short latency after spinal cord stimuli (1; arrowhead) and the absence of both overshoot (2) and undershoot (3).
