TY - JOUR
T1 - Neuromuscular system of the flexible arm of the octopus
T2 - Physiological characterization
AU - Matzner, Henry
AU - Gutfreund, Yoram
AU - Hochner, Binyamin
PY - 2000
Y1 - 2000
N2 - The octopus arm is an outstanding example of an efficient boneless and highly flexible appendage. We have begun characterizing the neuromuscular system of the octopus arm in both innervated muscle preparations and dissociated muscle cells. Functionally antagonistic longitudinal and transverse muscle fibers showed no differences in membrane properties and mode of innervation. The muscle cells are excitable but have a broad range of linear membrane properties. They are electrotonically very compact so that localized synaptic inputs can control the membrane potential of the entire muscle cell. Three distinct excitatory neuronal inputs to each arm muscle cell were identified; their reversal potentials were extrapolated to be about - 10 mV. These appear to be cholinergic as they are blocked by hexamethonium, D-tubocurarine, and atropine. Two inputs have low quantal amplitude (1-7 mV) and slow rise times (4-15 ms), whereas the third has a large size (5-25 mV) and fast rise time (2-4 ms). This large synaptic input is most likely due to exceptionally large quantal events. The probability of release is rather low, suggesting a stochastic activation of muscle cells. All inputs demonstrated a modest activity-dependent plasticity typical of fast neuromuscular systems. The pre- and postsynaptic properties suggest a rather direct relation between neuronal activity and muscle action. The lack of significant electrical coupling between muscle fibers and the indications for the small size of the motor units suggest that the neuromuscular system of the octopus arm has evolved to ensure a high level of precise localization in the neural control of arm function.
AB - The octopus arm is an outstanding example of an efficient boneless and highly flexible appendage. We have begun characterizing the neuromuscular system of the octopus arm in both innervated muscle preparations and dissociated muscle cells. Functionally antagonistic longitudinal and transverse muscle fibers showed no differences in membrane properties and mode of innervation. The muscle cells are excitable but have a broad range of linear membrane properties. They are electrotonically very compact so that localized synaptic inputs can control the membrane potential of the entire muscle cell. Three distinct excitatory neuronal inputs to each arm muscle cell were identified; their reversal potentials were extrapolated to be about - 10 mV. These appear to be cholinergic as they are blocked by hexamethonium, D-tubocurarine, and atropine. Two inputs have low quantal amplitude (1-7 mV) and slow rise times (4-15 ms), whereas the third has a large size (5-25 mV) and fast rise time (2-4 ms). This large synaptic input is most likely due to exceptionally large quantal events. The probability of release is rather low, suggesting a stochastic activation of muscle cells. All inputs demonstrated a modest activity-dependent plasticity typical of fast neuromuscular systems. The pre- and postsynaptic properties suggest a rather direct relation between neuronal activity and muscle action. The lack of significant electrical coupling between muscle fibers and the indications for the small size of the motor units suggest that the neuromuscular system of the octopus arm has evolved to ensure a high level of precise localization in the neural control of arm function.
UR - http://www.scopus.com/inward/record.url?scp=0034059323&partnerID=8YFLogxK
U2 - 10.1152/jn.2000.83.3.1315
DO - 10.1152/jn.2000.83.3.1315
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C2 - 10712459
AN - SCOPUS:0034059323
SN - 0022-3077
VL - 83
SP - 1315
EP - 1328
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
IS - 3
ER -