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Title: Membrane properties of cones and ganglion cells of the salamander retina
Author: Everett, Karen Elizabeth
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1990
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The aim of this thesis was to investigate the membrane properties of cone photoreceptors and ganglion cells of the salamander retina and to determine their role in the processing of the visual signal. Experimental investigations were carried out on cells in the intact retina and also in cells that had been isolated from the retina by enzymatic dissociation. Glutamate is thought to be the neurotransmitter released from vertebrate photoreceptors. Glutamate gates channels in postsynaptic bipolar and horizontal cells, but there have been no exhaustive studies of the effects of glutamate on the photoreceptors themselves. In patch-clamp recordings from both isolated cones and cones in the intact salamander retina, glutamate was found to activate a current carried largely by chloride ions, which is localized to the synaptic terminal of the cone. This suggests that glutamate released from a cone terminal may act on "autoreceptors" on that terminal, modulating its own release. This may be important as a mechanism for increasing the gain of cone phototransduction. The membrane properties of ganglion cells determine how visual information is coded for transmission to the brain. Ganglion cells have previously been shown to exist as at least two types, sustained and transient, in terms of the pattern of action potentials produced in response to illumination. The origin of transience in ganglion cells in unclear. Salamander ganglion cells show sustained or transient responses to the injection of current mimicking light-induced synaptic input. Using the whole-cell recording method, the properties of both voltage-gated currents and excitatory and inhibitory neurotransmitter-gated currents were investigated in voltage-clamped salamander ganglion cells. On the basis of these results, it is suggested that transience in the response of ganglion cells may in part be due to the properties of the voltage-gated membrane currents present in these cells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available