Excitatory Effects of Benzamil on the Sodium-Calcium Exchanger at the Crayfish Neuromuscular Junction

Abstract

In crayfish neurons, the sodium-calcium exchanger (NCX) pumps calcium ions out of the cell in exchange for sodium ions. The chemical benzamil has been found to be inhibitory to the NCX in crayfish antennal gland basolateral membrane vesicles (BLMVs) at concentrations under 30M and excitatory at higher concentrations (Wheatly et al. 2002). We predicted that concentrations of 60M and 100M would excite the neuromuscular junction (NMJ) of the crayfish tail, leading to lower EPSPs. We also attempted to determine whether the effects of benzamil are pre- or post-synaptic by analyzing ratios of EPSPs generated by paired-pulse stimulation. We found that benzamil was excitatory at 60M and 100M and the results of the paired-pulse stimulations suggest pre-synaptic effects.