Simultaneous application of H₂S and inhibition of its endogenous production induces disparate synaptic response at the crayfish neuromuscular junction

Abstract

Hydrogen sulfide (H₂S) has recently been identified as a gaseous neuromodulator of synaptic transmission. Within the cell, H₂S is synthesized via two distinct enzymatic pathways, one beginning with cystathionine ?-synthase (CBS) and the other with cystathionine ?-lyase (CSE). The objective of our research was to examine the role of H₂S, CBS, and CSE in synaptic transmission of the crayfish, a model organism in which, to our knowledge, no previous studies of this sort have been performed. To do so, we electrically induced an excitatory post-synaptic potential (EPSP), the amplitude of which is indicative of the extent of synaptic transmission. Measurements were taken under various chemical treatments: exogenous H₂S, CBS inhibition, CSE inhibition, or any combination thereof. Our results suggest that CBS plays a minor role in H₂S production whereas the role of CSE is more substantial. The presence of exogenous H₂S alone appears to have little impact, but in conjunction with a CBS or CSE inhibitor, H2S has two divergent responses. Most significant are the enlarged EPSPs that result from the application of a CSE inhibitor along with exogenous H₂S.