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W P Teubl

Publications and source records attributed to W P Teubl.

4 recordsLinked to original sources
PubMed1979

Estimates of cable parameters in lamprey spinal cord neurones.

1. Two micro-electrodes were used to penetrate giant interneurones in the isolated lamprey spinal cord. A brief (50--100 microsec) current pulse was applied to one electrode while the other recorded the voltage transient response. 2. A formal analysis of the voltage transient was achieved by the simplifying reduction of each neurone. Somas were treated as a parallel combination of resistance and capacitance. Dendrite trees were reduced to an equivalent cylinder (Rall, 1959). 3. The voltage transients were analysed according to the procedure suggested by Jack & Redman (1971b) to estimate the cable parameters governing the passive propagation of transmembrane potentials. Membrane time constant (tau m), dendritic to soma conductance ratio (rho 00), and electrotonic length (L) of the equivalent cylinder were estimated from these data. 4. In thirty-two interneurones it was possible to determine the membrane time constant, but rho 00 and L were determined in only twenty-two. 5. For the twenty-two neurones in which all cable parameters were estimated, the electrotonic length of the equivalent cylinder was similar to that found for cat spinal motoneurones (1--2 space constants). 6. Simulations of the voltage transient using the Rall model of the motoneurone as developed by Jack & Redman (1971b) resulted in a voltage response which closely ditted the experimental data. 7. These results suggest that the Rall model of the motoneurone accurately describes the propagation of passive transmembrane potentials in lamprey spinal cord neurones. It is further concluded that the time constant for soma and dendritic membrane is similar in these neurones.

Animals↗
PubMed1979

Localization of synaptic input on dendrites of a lamprey spinal cord neurone from physiological measurements of membrane properties.

1. Composite excitatory post-synaptic potentials (e.p.s.p.s) resulting from electrotonic and chemical synaptic junctions were recorded from eighteen interneurones following stimulation of the I2 burster axon in the isolated lamprey spinal cord. 2. In each cell, the half-width of the electrotonic e.p.s.p. was measured and used, together with the cable parameters estimated for the same neurone, to locate the position of synaptic contact made by the I2 axon on the dendrites of the interneurone. The synaptic location ranged from 0.05 to 1.35 space constants with a mean of 0.46. 3. The synaptic potential was simulated using the Rall model of the neurone. When compared with the experimentally recorded e.p.s.p. with the same half-width, the rise-time of the simulated synaptic potential was found to be faster. By changing the value of synaptic distance and/or synaptic current duration the half-width, rise-time, and decay of the simulated synaptic potential fit closely the experimental e.p.s.p. The range of synaptic distance estimated from the simulation decreased considerably (0.2--0.7 space constants; mean 0.52). 4. Direct comparison of synaptic location estimated from histological tracings of dendritic trees from these same cells injected with horseradish peroxidase compared favourably with synaptic location estimated from the simulations. 5. These results support the hypothesis that functionally similar presynaptic axons make synaptic connexions at the same electrotonic distance from the soma on functionally similar post-synaptic cells. This occurs in the face of large variations in physical distance for these same synaptic contacts.

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