Inhibiting reverse-mode operation of the Na+/Ca2+ exchanger does not affect long-term facilitation in crayfish neuromuscular junction

Abstract

High frequency stimulation of a crayfish neuron results in a long-term facilitation (LTF) of synaptic transmission of neurotransmitters across the neuromuscular junction. After LTF is induced, the Na+/Ca2+ exchangers begin working in a reverse mode, expelling three Na+ ions and admitting one Ca2+ ion into the cell. We hypothesized that inhibiting the reverse mode of the Na+/Ca2+ exchanger with the chemical SN-6 would result in a decrease in postsynaptic EPSPs after low frequency (10 Hz) stimulation for a minute following high frequency stimulation (20 Hz) for 10 minutes. We then recorded EPSPs before and after both the long and short term LTF-inducing tetani. The difference in means of our EPSPs showed had no statistical significance (p>0.05).