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Long-lasting synaptic potentials and the modulation of synaptic transmission
Federation Proceedings
|June 1, 1979
Summary
Long-lasting synaptic potentials in bullfrog sympathetic neurons enhance fast excitatory postsynaptic potentials (EPSPs), increasing synaptic transmission efficacy. This modulation is postsynaptic and long-lasting, but cyclic nucleotides are not the underlying second messengers.
Area of Science:
- Neuroscience
- Synaptic Transmission
- Cellular Electrophysiology
Background:
- Long-lasting postsynaptic potentials (PSPs) are generated by decreased membrane conductance in various neurons.
- Understanding the role of these conductance-decrease PSPs in synaptic modulation is crucial.
- The molecular mechanisms underlying conductance-decrease PSPs require further investigation.
Purpose of the Study:
- To investigate the role of long-lasting conductance decreases in modulating synaptic transmission in bullfrog sympathetic ganglia.
- To explore the molecular basis of conductance-decrease PSP generation.
- To determine if cyclic nucleotides act as second messengers in slow PSP generation.
Main Methods:
- Electrophysiological recordings in bullfrog sympathetic ganglia.
- Iontophoretic application of methacholine to activate muscarinic receptors.
- Stimulation of separate synaptic pathways to elicit noncholinergic slow PSPs.
- Biochemical assays to measure cyclic AMP and cyclic GMP levels.
- Electrophysiological analysis of cyclic nucleotide actions.
Main Results:
- Synaptic activation of muscarinic receptors generated a slow excitatory postsynaptic potential (EPSP) with decreased membrane conductance.
- Methacholine application and noncholinergic late-slow EPSPs enhanced the amplitude and duration of conventional fast EPSPs.
- This enhancement increased the probability of action potential generation, thereby improving synaptic transmission efficacy.
- Stimulation of one pathway enhanced transmission in another via a postsynaptic mechanism.
- Synaptic stimulation increased ganglionic cyclic AMP and cyclic GMP, but these nucleotides did not mediate the slow PSPs.
Conclusions:
- Stimulation of one synaptic pathway can enhance the efficacy of a second pathway through a long-lasting postsynaptic mechanism.
- This modulation of synaptic efficacy is mediated by conductance-decrease PSPs.
- Cyclic AMP and cyclic GMP are unlikely to be the intracellular second messengers responsible for the observed membrane permeability changes.