Effect of temperature on a voltage-sensitive electrical synapse in crayfish

Area of Science:

• Neuroscience
• Animal Physiology
• Biophysics

Background:

• The giant motor synapse (GMS) is crucial for the crayfish's fast reflex escape pathway.
• Temperature sensitivity of synaptic transmission is vital for understanding neural circuit function across environments.
• A mismatch in Q10 values between the GMS and connected neurons (LG, MoG) prompted this investigation.

Purpose of the Study:

• To investigate the effects of temperature on synaptic transmission through the crayfish GMS.
• To reconcile the apparent discrepancy between the high Q10 of GMS activation and the lower Q10 of LG/MoG membrane properties.
• To determine how temperature influences the effectiveness of the escape reflex circuit.

Main Methods:

• Experimental investigation of crayfish nerve cord preparations.
• Computer simulations of synaptic transmission dynamics.
• Analysis of presynaptic spike duration, GMS current transfer, and MoG excitability at varying temperatures.

Main Results:

• Contrary to the initial hypothesis, synaptic transmission through the GMS was more reliable at lower temperatures.
• Transmission failed at upper temperature limits (12-25°C in isolated preparations, >30°C in semi-intact preparations).
• Lower temperatures increased presynaptic spike duration and MoG excitability, enhancing transmission effectiveness.

Conclusions:

• The crayfish escape circuit operates effectively across a wider temperature range due to the GMS's properties.
• High Q10 of GMS activation preserves transmission at higher temperatures, extending operational range.
• Temperature-dependent changes in spike duration and neuronal excitability optimize synaptic function.