Sets of synaptic currents paired by common presynaptic or postsynaptic neurons

Area of Science:

• Neuroscience
• Cellular Biology
• Synaptic Plasticity

Background:

• Presynaptic neurons B4 and B5 in Aplysia buccal ganglia generate inhibitory postsynaptic currents (PSCs).
• Previous research indicates variability in PSC duration and amplitude, impacting synaptic efficacy.
• Transient alterations in PSC parameters can be induced by manipulating presynaptic activity.

Purpose of the Study:

• To enable synapse-to-synapse comparisons of synaptic current parameters.
• To quantify the mean and coefficient of variation (CV) of peak conductance (gpeak) and time constant of decay (tau) for PSCs.
• To investigate the presynaptic and postsynaptic contributions to PSC efficacy and variability.

Main Methods:

• Direct intracellular stimulation of presynaptic neurons to evoke synaptic currents.
• Recording of synaptic currents from postsynaptic follower cells.
• Analysis of peak conductance (gpeak) and time constant of decay (tau) using mean and CV.
• Examination of three-cell networks with paired presynaptic inputs converging on a common postsynaptic cell.

Main Results:

• For 56 synapses, mean gpeak was 0.40 ± 0.33 μS (CV=0.83) and mean tau was 19.7 ± 4.0 ms (CV=0.20).
• Synapse-to-synapse variability was consistent with previous population data (within 5%).
• In paired input scenarios, gpeak and tau were significantly more similar in a common postsynaptic cell than in different followers (P<0.001), indicating postsynaptic influence on parameter similarity.

Conclusions:

• The study quantifies key parameters of inhibitory postsynaptic currents (PSCs) in Aplysia.
• Both presynaptic and postsynaptic factors contribute to the efficacy and variability of PSCs.
• While postsynaptic cells influence the similarity of synaptic parameters, they do not constrain overall variability.