Influence of the extracellular ionic environment on ganglionic fast excitatory postsynaptic currents

Area of Science:

• Neuroscience
• Cellular Electrophysiology

Background:

• Nicotinic fast excitatory postsynaptic currents (EPSCs) are crucial for neuronal communication.
• Extracellular ion concentrations significantly influence synaptic transmission characteristics.

Purpose of the Study:

• To investigate the effects of altering extracellular sodium and calcium concentrations, and adding strontium or magnesium on bullfrog sympathetic B cell nicotinic EPSCs.
• To elucidate the specific role of lithium substitution for sodium in modulating EPSC properties.

Main Methods:

• Voltage-clamped sympathetic ganglion B cells from bullfrogs were utilized.
• Nicotinic fast excitatory postsynaptic currents (EPSCs) were recorded under varying extracellular ionic conditions, including lithium substitution for sodium.

Main Results:

• Lithium substitution for sodium concentration-dependently affected EPSC size and decay time course.
• Higher lithium concentrations (100%) led to a faster EPSC decay and a significant reduction in EPSC size compared to controls.
• The observed changes were attributed to the presence of lithium, not merely the reduced external sodium concentration, as sucrose or mannitol substitution slowed EPSC decay.

Conclusions:

• Lithium ions directly influence the kinetics and amplitude of nicotinic EPSCs in bullfrog sympathetic neurons.
• The findings highlight the specific role of sodium ions and the disruptive effect of lithium on synaptic transmission mechanisms.