Meeting Abstract
We are addressing two issues: (1) the influence of pHi on vesicular packaging of neurotransmitter; (2) response of glutamate receptors on postsynaptic targets with altering extracellular and intracellular pH. These investigations are being addressed at the model crayfish and Drosophila neuromuscular junctions (NMJs). These two projects are interrelated as transmission at glutamatergic synapses is retarded in the presence of CO2 which cannot be fully accounted for by a reduced pHi within the presynaptic nerve terminal or within the postsynaptic muscle fiber since the EPSPs increase in amplitude with rebound acidification after a pulse of NH4Cl. High (40 mM) proprionic acid acidifies both the pre- and post-synaptic cells. When used the frequency and amplitude of mini’s increases despite a slight membrane depolarization. However, evoked transmission is blocked. The use of high [CO2] containing saline blocks evoked and mini’s as well as the sensitivity of glutamate receptors. These NMJs are glutamatergic and the evoked (non-spiking) synaptic potentials and spontaneous (quantal) events are readily measured. Addressing the mechanisms underlying these observed phenomena may help in understanding synaptic depression after high frequency stimulation and feedback process in synaptic transmission. These studies tackle fundamental principles which are likely present in glutamatergic neurons for all animals.
