2-APB Negates the Enhancement of EPSP Amplitudes Induced by 5-HT in the <em>Procambaris clarkii</em> Neuromuscular Junction.

Abstract

5-HT is known to increase the amplitude of excitatory postsynaptic potentials (EPSPs) in the crayfish neuromuscular junction, but it is not known how 5-HT does this. It is possible that 5-HT acts through IP₃-induced intracellular Ca²⁺ release. To test this, we bathed a crayfish neuromuscular junction in a solution of 5-HT plus the IP₃ inhibitor 2-APB and measured EPSP amplitudes. We compared these with EPSP measurements taken in a solution with 5-HT alone. We found that the application of the IP₃ inhibitor counteracts the amplitude-increasing effect of 5-HT. This supports our hypothesis that 5-HT works through IP₃-induced Ca²⁺ increase to increase the amplitudes of EPSPs in the crayfish neuromuscular junction.