Passive Electrical Properties of Horizontal Cells in the Retina of the Turtle, Pseudemys Scripta Elegans

A core conductor analysis was applied to the passive relaxation of the transmembrane potential in response to 20 ms pulses of current in luminosity-type and chromaticity-type horizontal cells. The time course of the relaxation was described by the sum of two exponentially decaying processes. The passive responses were analyzed in terms of a finite cable model; values for equivalent electrotonic length (L) and dendrite:soma conductance ratio ((rho)) were calculated for each cell. Luminosity-type cells could be divided into two populations on the basis of their values for L and (rho). The larger population had mean values for L and (rho) in the dark of 1.4 and 6.8, respectively; these probably represented H1 cell bodies. The smaller population had a mean value for L in the dark of 0.8 and a mean value for (rho) in excess of 20 (the largest measurable value); these probably represented H1 axon terminals. The relatively small values for L and large values for (rho) observed in all luminosity-type cells mean that a post-synaptic signal, introduced at the distal end of a dendrite, can spread passively along the dendrite, cross the soma, and enter the adjacent dendrites with little loss of amplitude. This demonstrates an integrative role for the horizontal cell dendrites that had previously been only inferred.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biophysics

Grantor

University of Illinois at Urbana-Champaign

Date dc:date

10000-01-01

Author dc:creator

• Carras, Peter Lewis

• Biophysics, General

Identifier

(UMI)AAI8409883

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70710