Actions of NCX, PMCA and SERCA on Short-Term Facilitation and Maintenance of Transmission in Nerve Terminals~!2010-03-10~!2010-08-23~!2010-09-08~!

Abstract

Residual Ca 2+ can accumulate in the nerve terminal during repetitive stimulation; thus, the basis for short-term facilitation (STF). The plasmalemmal Na + /Ca 2+ exchanger [NCX], the Ca 2+-ATPase (PMCA) and the sarcoplasmic/endoplasmic reticulum Ca 2+-ATPase (SERCA) on the endoplasmic reticulum are three important Ca 2+ regulatory processes in controlling [Ca 2+ ] i. The role of these [Ca 2+ ] i regulators in the development and maintenance of STF was addressed at the neuromuscular junction. When the NCX is compromised by reduced [Na + ] o , the EPSP amplitudes decrease, but with KB-R7943 (a reverse blocker of NCX) the amplitude increases. Compromising the PMCA with pH 8.8 produces an increase in EPSP amplitudes, but treatments with carboxyeosin (a blocker of PMCA) produced mixed results. Blocking the SERCA increases EPSP amplitudes. Facilitation was only slighted altered in some conditions with these manipulations. The results support the view that release is not saturated during a plateau phase of STF since the terminal is able to reach a new plateau with higher stimulation frequency or an altered [Ca 2+ ] i. Multiple approaches in compromising the NCX and PMCA are presented. These findings are significant because there is a rapid alteration in transmission when compromising Ca 2+ extrusion mechanisms during STF.

The acute and chronic effect of low temperature on survival, heart rate and neural function in crayfish (<i>Procambarus clarkii</i>) and prawn (<i>Macrobrachium rosenbergii</i>) species

“…Also, how an alteration in these calcium regulating proteins might influence synaptic transmission in relation to acclimation has yet to be investigated. However, the role of calcium transport and exchangers in synaptic transmission has been investigated for the crayfish and Drosophila NMJs [38,39] and for the Drosophila heart [40] at room temperature. The cellular properties that have been suggested to allow invertebrates to acclimate to cold environments focus mainly on a means to maintain membrane fluidity, by alteration in the phospholipid composition, as well as an alteration in the make up of the hemolymph to avoid freezing [41][42][43][44][45].…”

The Mechanistic Action of Carbon Dioxide on a Neural Circuit and NMJ Communication

“…Empirical evidence to a general mechanism of action of anesthetics involves physical changes in permeability of the cell membrane (Mullins, ). Permeability changes can come about by alteration in the permeability of leak channels, exchangers or even activity of the various ionic pumps (Desai‐Shah and Cooper, ) and vesicle recycling/packaging within nerve terminals (Wu and Cooper, , ).…”