5-HT-activated Ryanodine Receptors Play an Active Role in Increasing Excitatory Post-synaptic Potentials at the Crayfish Neuromuscular Junction

Abstract

In this experiment, we investigated the role of serotonin(5-HT)-activated ryanodine receptors in the dorsal superficial extensor muscle cells in the tail of the crayfish (Procambarous clarkii). We hypothesized that the 5-HT-activated ryanodine receptors are responsible for some of the Ca²⁺ released in the pre-synaptic cell, and consequently for the heightened amplitudes of the generated Excitatory Post-Synaptic Potentials (EPSPs). To test this hypothesis we measured, using intracellular recording, the amplitudes of EPSPs generated by stimulating individual crayfish nerves under various conditions. We collected baseline data when the crayfish muscle cells were exposed to standard crayfish solution, and compared that with measurements collected when the crayfish cells were exposed to 5-HT, Ruthenium Red, and the two combined. Ruthenium Red blocks ryanodine receptors. Overall, our results support our hypothesis. The presence of 5-HT increased EPSPs, while Ruthenium Red had little effect; when we added Ruthenium Red and 5-HT together, the amplitudes of the EPSPs remained essentially the same as before the addition of 5-HT, signifying that when the ryanodine receptors are blocked, 5-HT has no effect.