Citrate and NTA not suitable as extracellular calcium buffers at the crayfish neuromuscular junction

Abstract

Previous research has suggested that the calcium buffers citrate and/or nitrilotriacetic acid (NTA) may alter neurotransmitter release at the neuromuscular junction, allowing researchers to investigate the role of fluctuations in calcium concentrations outside the pre-synaptic terminal. To examine the effects of these chemicals, this research set out to measure changes in excitatory post-synaptic potentials (EPSPs) caused by citrate and NTA at the crayfish neuromuscular junction. Using standard intracellular recording and extracellular stimulation techniques, we measured EPSP amplitudes in magnesium-free, low calcium Ringers solutions and in two solutions with citrate and NTA added separately. We experienced great difficulty in recording control data and were unsuccessful in recording any data for the buffered solutions. This result suggests that the lowered calcium concentration (required for NTA and citrate to act as buffers) combined with the lack of magnesium in the solutions interferes with the normal stimulation of an EPSP. This calls into question the suitability of citrate and NTA as calcium buffers at the crayfish neuromuscular junction.