Response to prolonged and repetitive stimulation of identified giant neurons in the brain of helix aspersa
Response to prolonged and repetitive stimulation of identified giant neurons in the brain of helix aspersa
Spontaneous action potentials and post synaptic potentials were recorded intracellularly in giant neurones of Helix aspersa. In some cells, facilitation of unitary post synaptic responses was observed on repeated stimulation of the anal nerve. Pharmacological investigation of the biphasic evoked responses recorded in E16 and E17 suggests they are mediated by dopamine and glutamate respectively. The inhibitory phase of the response underwent facilitation when stimuli were paired. Facilitation outlasted the first response by 0. 5 seconds in E16 and 11 seconds in E17. By comparison, facilitation of evoked EPSPs in cell E15 lasted 1.0 second. Properties of the cell membrane were unaffected. High calcium saline increased the size of spontaneous and evoked potentials and also reduced the magnitude of facilitation. High magnesium had the reverse i effect.On repetitive stimulation at 0.5-4.0 pulses per second, facilitation developed slowly and outlasted stimulation by 30-60 seconds. The maximum facilitation was independent of calcium ion concentration. At 8.0-60 pulses per second, post tetanic potentiation developed. This resulted in greater increases in response amplitude than facilitation, and persisted for 3-5 minutes. Both amplitude and duration depended on the number of conditioning stimuli. Heterosynaptic facilitation was demonstrated in a number of cells. Facilitation was often seen during recordings of spontaneous potentials.Responses of cells to directly injected currents were investigated. The time constant of excitation was longer in silent than in active cells. The firing freq-. uency of all cells declined on prolonged stimulation. The adaptation of cells was related to the after hyperpolarisation amplitude, and was accompanied by, changes in shape of action potentials and an increase in membrane resistance.Two cell groups were identified in which either the rising or the falling phase of the AP was modified during the response.Implications for plasticity of response at pre- and post-synaptic levels are discussed.
University of Southampton
1976
Haynes, Lawrence William
(1976)
Response to prolonged and repetitive stimulation of identified giant neurons in the brain of helix aspersa.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Spontaneous action potentials and post synaptic potentials were recorded intracellularly in giant neurones of Helix aspersa. In some cells, facilitation of unitary post synaptic responses was observed on repeated stimulation of the anal nerve. Pharmacological investigation of the biphasic evoked responses recorded in E16 and E17 suggests they are mediated by dopamine and glutamate respectively. The inhibitory phase of the response underwent facilitation when stimuli were paired. Facilitation outlasted the first response by 0. 5 seconds in E16 and 11 seconds in E17. By comparison, facilitation of evoked EPSPs in cell E15 lasted 1.0 second. Properties of the cell membrane were unaffected. High calcium saline increased the size of spontaneous and evoked potentials and also reduced the magnitude of facilitation. High magnesium had the reverse i effect.On repetitive stimulation at 0.5-4.0 pulses per second, facilitation developed slowly and outlasted stimulation by 30-60 seconds. The maximum facilitation was independent of calcium ion concentration. At 8.0-60 pulses per second, post tetanic potentiation developed. This resulted in greater increases in response amplitude than facilitation, and persisted for 3-5 minutes. Both amplitude and duration depended on the number of conditioning stimuli. Heterosynaptic facilitation was demonstrated in a number of cells. Facilitation was often seen during recordings of spontaneous potentials.Responses of cells to directly injected currents were investigated. The time constant of excitation was longer in silent than in active cells. The firing freq-. uency of all cells declined on prolonged stimulation. The adaptation of cells was related to the after hyperpolarisation amplitude, and was accompanied by, changes in shape of action potentials and an increase in membrane resistance.Two cell groups were identified in which either the rising or the falling phase of the AP was modified during the response.Implications for plasticity of response at pre- and post-synaptic levels are discussed.
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Published date: 1976
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Local EPrints ID: 458702
URI: http://eprints.soton.ac.uk/id/eprint/458702
PURE UUID: 064d91d4-ef85-4629-b2ea-16e3d53eeaf9
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Date deposited: 04 Jul 2022 16:54
Last modified: 04 Jul 2022 16:54
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Author:
Lawrence William Haynes
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