Serotonin does not increase the EPSP amplitude and IP3 does not decrease the EPSP amplitude in Orconectes neuromuscular junction

Abstract

Serotonin (5-HT) is a neuromodulator known to facilitate neurotransmission in the neuromuscular junction (NMJ). It binds to presynaptic receptors, and activates G-proteins which then leads to the activation of second messenger molecule called IP3. Our goal was to investigate whether IP3 causes the release of internal Ca2+, leading to facilitation. We investigated the effects of 5-HT and the role of IP3 in crayfish (Orconectes) synaptic transmission. We hypothesized that 5-HT would increase the excitatory post-synaptic potential (EPSP) amplitude in crayfish (Orconectes) NMJ. Furthermore, we hypothesized that the inhibition of IP3 receptors using 2-APB would block the effects of 5-HT and therefore prevent facilitation. In our experiment, 5-HT led to EPSP decreasing by 26%. The addition of 2-APB with 5-HT solution led to 61% higher EPSP amplitude compared to control (saline solution). However, our t-test (p>.05) showed that these differences were not significant. Thus, our results show that 5-HT and 2-APB do not affect the EPSP amplitude in the crayfish (Orconectes) NMJ.