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Enhanced synaptic transmission at the squid giant synapse by artificial seawater based on physically modified saline.

Choi S, Yu E, Rabello G, Merlo S, Zemmar A, Walton KD, Moreno H, Moreira JE, Sugimori M, Llinás RR - Front Synaptic Neurosci (2014)

Bottom Line: Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites.Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW.After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles.

View Article: PubMed Central - PubMed

Affiliation: Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA.

ABSTRACT
Superfusion of the squid giant synapse with artificial seawater (ASW) based on isotonic saline containing oxygen nanobubbles (RNS60 ASW) generates an enhancement of synaptic transmission. This was determined by examining the postsynaptic response to single and repetitive presynaptic spike activation, spontaneous transmitter release, and presynaptic voltage clamp studies. In the presence of RNS60 ASW single presynaptic stimulation elicited larger postsynaptic potentials (PSP) and more robust recovery from high frequency stimulation than in control ASW. Analysis of postsynaptic noise revealed an increase in spontaneous transmitter release with modified noise kinetics in RNS60 ASW. Presynaptic voltage clamp demonstrated an increased EPSP, without an increase in presynaptic ICa(++) amplitude during RNS60 ASW superfusion. Synaptic release enhancement reached stable maxima within 5-10 min of RNS60 ASW superfusion and was maintained for the entire recording time, up to 1 h. Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites. Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW. After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles. The possibility that RNS60 ASW acts by increasing mitochondrial ATP synthesis was tested by direct determination of ATP levels in both presynaptic and postsynaptic structures. This was implemented using luciferin/luciferase photon emission, which demonstrated a marked increase in ATP synthesis following RNS60 administration. It is concluded that RNS60 positively modulates synaptic transmission by up-regulating ATP synthesis, thus leading to synaptic transmission enhancement.

No MeSH data available.


Related in: MedlinePlus

Example of recovery of evoked transmitter release by RNS60 ASW in a hypoxic synapse following electrical stimulation of the presynaptic terminal. Note small subthreshold synaptic potential after 30 min of hypoxia (lower arrow) and EPSP (upper arrow) and action potential elicited 3 min after superfusion with RNS60 ASW. Insert, amplitude magnification showing detail of the EPSP onset indicating change in amplitude without a change in release latency.
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Figure 1: Example of recovery of evoked transmitter release by RNS60 ASW in a hypoxic synapse following electrical stimulation of the presynaptic terminal. Note small subthreshold synaptic potential after 30 min of hypoxia (lower arrow) and EPSP (upper arrow) and action potential elicited 3 min after superfusion with RNS60 ASW. Insert, amplitude magnification showing detail of the EPSP onset indicating change in amplitude without a change in release latency.

Mentions: As originally demonstrated by Bryant (1958) and by Colton et al. (1992), synaptic transmission fails within 30 min when synapses are not properly oxygenated. This is due to transmitter depletion following hypoxia (Colton et al., 1992). Our initial set of experiments was designed to determine whether RNS60 could restore normal transmission in hypoxic synapses without having deleterious effects. These experiments consisted of allowing postsynaptic amplitude to decline such that only small, subthreshold postsynaptic synaptic potentials could be elicited (Figure 1, lower arrow). At that point, superperfusion with RNS60 ASW produced an increase in the postsynaptic potential, to the point that a postsynaptic spike could be easily evoked by each presynaptic stimulus. The action potential in Figure 1 was recorded 3 min after changing to RNS60 ASW. Such recordings could be made with long-term superfusion of RNS60 ASW, up to several hours. This demonstrates that RSN60 can rapidly and effectively restore transmission after hypoxic failure and does not itself have a deleterious effect on the transmission event as seen with oxygenated ASW (Colton et al., 1992).


Enhanced synaptic transmission at the squid giant synapse by artificial seawater based on physically modified saline.

Choi S, Yu E, Rabello G, Merlo S, Zemmar A, Walton KD, Moreno H, Moreira JE, Sugimori M, Llinás RR - Front Synaptic Neurosci (2014)

Example of recovery of evoked transmitter release by RNS60 ASW in a hypoxic synapse following electrical stimulation of the presynaptic terminal. Note small subthreshold synaptic potential after 30 min of hypoxia (lower arrow) and EPSP (upper arrow) and action potential elicited 3 min after superfusion with RNS60 ASW. Insert, amplitude magnification showing detail of the EPSP onset indicating change in amplitude without a change in release latency.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921564&req=5

Figure 1: Example of recovery of evoked transmitter release by RNS60 ASW in a hypoxic synapse following electrical stimulation of the presynaptic terminal. Note small subthreshold synaptic potential after 30 min of hypoxia (lower arrow) and EPSP (upper arrow) and action potential elicited 3 min after superfusion with RNS60 ASW. Insert, amplitude magnification showing detail of the EPSP onset indicating change in amplitude without a change in release latency.
Mentions: As originally demonstrated by Bryant (1958) and by Colton et al. (1992), synaptic transmission fails within 30 min when synapses are not properly oxygenated. This is due to transmitter depletion following hypoxia (Colton et al., 1992). Our initial set of experiments was designed to determine whether RNS60 could restore normal transmission in hypoxic synapses without having deleterious effects. These experiments consisted of allowing postsynaptic amplitude to decline such that only small, subthreshold postsynaptic synaptic potentials could be elicited (Figure 1, lower arrow). At that point, superperfusion with RNS60 ASW produced an increase in the postsynaptic potential, to the point that a postsynaptic spike could be easily evoked by each presynaptic stimulus. The action potential in Figure 1 was recorded 3 min after changing to RNS60 ASW. Such recordings could be made with long-term superfusion of RNS60 ASW, up to several hours. This demonstrates that RSN60 can rapidly and effectively restore transmission after hypoxic failure and does not itself have a deleterious effect on the transmission event as seen with oxygenated ASW (Colton et al., 1992).

Bottom Line: Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites.Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW.After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles.

View Article: PubMed Central - PubMed

Affiliation: Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA.

ABSTRACT
Superfusion of the squid giant synapse with artificial seawater (ASW) based on isotonic saline containing oxygen nanobubbles (RNS60 ASW) generates an enhancement of synaptic transmission. This was determined by examining the postsynaptic response to single and repetitive presynaptic spike activation, spontaneous transmitter release, and presynaptic voltage clamp studies. In the presence of RNS60 ASW single presynaptic stimulation elicited larger postsynaptic potentials (PSP) and more robust recovery from high frequency stimulation than in control ASW. Analysis of postsynaptic noise revealed an increase in spontaneous transmitter release with modified noise kinetics in RNS60 ASW. Presynaptic voltage clamp demonstrated an increased EPSP, without an increase in presynaptic ICa(++) amplitude during RNS60 ASW superfusion. Synaptic release enhancement reached stable maxima within 5-10 min of RNS60 ASW superfusion and was maintained for the entire recording time, up to 1 h. Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites. Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW. After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles. The possibility that RNS60 ASW acts by increasing mitochondrial ATP synthesis was tested by direct determination of ATP levels in both presynaptic and postsynaptic structures. This was implemented using luciferin/luciferase photon emission, which demonstrated a marked increase in ATP synthesis following RNS60 administration. It is concluded that RNS60 positively modulates synaptic transmission by up-regulating ATP synthesis, thus leading to synaptic transmission enhancement.

No MeSH data available.


Related in: MedlinePlus