5-HT3R–sourced calcium enhances glutamate release from a distinct vesicle pool

Jessica A. Fawley, Mark W. Doyle, Michael Andresen

Research output: Contribution to journalArticle

Abstract

The serotonin 3 receptor (5-HT3R) is a calcium-permeant channel heterogeneously expressed in solitary tract (ST) afferents. ST afferents synapse in the nucleus of the solitary tract (NTS) and rely on a mix of voltage-dependent calcium channels (CaVs) to control synchronous glutamate release (ST-EPSCs). CaV activation triggers additional, delayed release of glutamate (asynchronous EPSCs) that trails after the ST-EPSCs but only from afferents expressing the calcium-permeable, transient receptor potential vanilloid type 1 receptor (TRPV1). Most afferents express TRPV1 and have high rates of spontaneous glutamate release (sEPSCs) that is independent of CaVs. Here, we tested whether 5-HT3R-sourced calcium contributes to these different forms of glutamate release in horizontal NTS slices from rats. The 5-HT3R selective agonist, m-chlorophenyl biguanide hydrochloride (PBG), enhanced sEPSCs and/or delayed the arrival times of ST-EPSCs (i.e. increased latency). The specific 5-HT3R antagonist, ondansetron, attenuated these effects consistent with direct activation of 5-HT3Rs. PBG did not alter ST-EPSC amplitude or asynchronous EPSCs. These independent actions suggest two distinct 5-HT3R locations; axonal expression that impedes conduction and terminal expression that mobilizes a spontaneous vesicle pool. Calcium chelation with EGTA-AM attenuated the frequency of 5-HT3R-activated sEPSCs by half. The mixture of chelation-sensitive and resistant sEPSCs suggests that 5-HT3R-activated vesicles span calcium diffusion distances that are both distal (micro-) and proximal (nanodomains) to the channel. Our results demonstrate that the calcium domains of 5-HT3Rs do not overlap other calcium sources or their respective vesicle pools. 5-HT3Rs add a unique calcium source on ST afferents as part of multiple independent synaptic signaling mechanisms.

Original languageEnglish (US)
Article number146346
JournalBrain research
Volume1721
DOIs
StatePublished - Oct 15 2019

Fingerprint

Glutamic Acid
Calcium
Calcium Channels
Biguanides
Receptors, Serotonin, 5-HT3
Ondansetron
Solitary Nucleus
Synapses

Keywords

  • 5-HTR
  • Calcium domains
  • Glutamate release
  • NTS
  • TRPV1
  • Vesicle pools

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

Cite this

5-HT3R–sourced calcium enhances glutamate release from a distinct vesicle pool. / Fawley, Jessica A.; Doyle, Mark W.; Andresen, Michael.

In: Brain research, Vol. 1721, 146346, 15.10.2019.

Research output: Contribution to journalArticle

@article{561e2d4daf4d4a489825e2374c254d8f,
title = "5-HT3R–sourced calcium enhances glutamate release from a distinct vesicle pool",
abstract = "The serotonin 3 receptor (5-HT3R) is a calcium-permeant channel heterogeneously expressed in solitary tract (ST) afferents. ST afferents synapse in the nucleus of the solitary tract (NTS) and rely on a mix of voltage-dependent calcium channels (CaVs) to control synchronous glutamate release (ST-EPSCs). CaV activation triggers additional, delayed release of glutamate (asynchronous EPSCs) that trails after the ST-EPSCs but only from afferents expressing the calcium-permeable, transient receptor potential vanilloid type 1 receptor (TRPV1). Most afferents express TRPV1 and have high rates of spontaneous glutamate release (sEPSCs) that is independent of CaVs. Here, we tested whether 5-HT3R-sourced calcium contributes to these different forms of glutamate release in horizontal NTS slices from rats. The 5-HT3R selective agonist, m-chlorophenyl biguanide hydrochloride (PBG), enhanced sEPSCs and/or delayed the arrival times of ST-EPSCs (i.e. increased latency). The specific 5-HT3R antagonist, ondansetron, attenuated these effects consistent with direct activation of 5-HT3Rs. PBG did not alter ST-EPSC amplitude or asynchronous EPSCs. These independent actions suggest two distinct 5-HT3R locations; axonal expression that impedes conduction and terminal expression that mobilizes a spontaneous vesicle pool. Calcium chelation with EGTA-AM attenuated the frequency of 5-HT3R-activated sEPSCs by half. The mixture of chelation-sensitive and resistant sEPSCs suggests that 5-HT3R-activated vesicles span calcium diffusion distances that are both distal (micro-) and proximal (nanodomains) to the channel. Our results demonstrate that the calcium domains of 5-HT3Rs do not overlap other calcium sources or their respective vesicle pools. 5-HT3Rs add a unique calcium source on ST afferents as part of multiple independent synaptic signaling mechanisms.",
keywords = "5-HTR, Calcium domains, Glutamate release, NTS, TRPV1, Vesicle pools",
author = "Fawley, {Jessica A.} and Doyle, {Mark W.} and Michael Andresen",
year = "2019",
month = "10",
day = "15",
doi = "10.1016/j.brainres.2019.146346",
language = "English (US)",
volume = "1721",
journal = "Brain Research",
issn = "0006-8993",
publisher = "Elsevier",

}

TY - JOUR

T1 - 5-HT3R–sourced calcium enhances glutamate release from a distinct vesicle pool

AU - Fawley, Jessica A.

AU - Doyle, Mark W.

AU - Andresen, Michael

PY - 2019/10/15

Y1 - 2019/10/15

N2 - The serotonin 3 receptor (5-HT3R) is a calcium-permeant channel heterogeneously expressed in solitary tract (ST) afferents. ST afferents synapse in the nucleus of the solitary tract (NTS) and rely on a mix of voltage-dependent calcium channels (CaVs) to control synchronous glutamate release (ST-EPSCs). CaV activation triggers additional, delayed release of glutamate (asynchronous EPSCs) that trails after the ST-EPSCs but only from afferents expressing the calcium-permeable, transient receptor potential vanilloid type 1 receptor (TRPV1). Most afferents express TRPV1 and have high rates of spontaneous glutamate release (sEPSCs) that is independent of CaVs. Here, we tested whether 5-HT3R-sourced calcium contributes to these different forms of glutamate release in horizontal NTS slices from rats. The 5-HT3R selective agonist, m-chlorophenyl biguanide hydrochloride (PBG), enhanced sEPSCs and/or delayed the arrival times of ST-EPSCs (i.e. increased latency). The specific 5-HT3R antagonist, ondansetron, attenuated these effects consistent with direct activation of 5-HT3Rs. PBG did not alter ST-EPSC amplitude or asynchronous EPSCs. These independent actions suggest two distinct 5-HT3R locations; axonal expression that impedes conduction and terminal expression that mobilizes a spontaneous vesicle pool. Calcium chelation with EGTA-AM attenuated the frequency of 5-HT3R-activated sEPSCs by half. The mixture of chelation-sensitive and resistant sEPSCs suggests that 5-HT3R-activated vesicles span calcium diffusion distances that are both distal (micro-) and proximal (nanodomains) to the channel. Our results demonstrate that the calcium domains of 5-HT3Rs do not overlap other calcium sources or their respective vesicle pools. 5-HT3Rs add a unique calcium source on ST afferents as part of multiple independent synaptic signaling mechanisms.

AB - The serotonin 3 receptor (5-HT3R) is a calcium-permeant channel heterogeneously expressed in solitary tract (ST) afferents. ST afferents synapse in the nucleus of the solitary tract (NTS) and rely on a mix of voltage-dependent calcium channels (CaVs) to control synchronous glutamate release (ST-EPSCs). CaV activation triggers additional, delayed release of glutamate (asynchronous EPSCs) that trails after the ST-EPSCs but only from afferents expressing the calcium-permeable, transient receptor potential vanilloid type 1 receptor (TRPV1). Most afferents express TRPV1 and have high rates of spontaneous glutamate release (sEPSCs) that is independent of CaVs. Here, we tested whether 5-HT3R-sourced calcium contributes to these different forms of glutamate release in horizontal NTS slices from rats. The 5-HT3R selective agonist, m-chlorophenyl biguanide hydrochloride (PBG), enhanced sEPSCs and/or delayed the arrival times of ST-EPSCs (i.e. increased latency). The specific 5-HT3R antagonist, ondansetron, attenuated these effects consistent with direct activation of 5-HT3Rs. PBG did not alter ST-EPSC amplitude or asynchronous EPSCs. These independent actions suggest two distinct 5-HT3R locations; axonal expression that impedes conduction and terminal expression that mobilizes a spontaneous vesicle pool. Calcium chelation with EGTA-AM attenuated the frequency of 5-HT3R-activated sEPSCs by half. The mixture of chelation-sensitive and resistant sEPSCs suggests that 5-HT3R-activated vesicles span calcium diffusion distances that are both distal (micro-) and proximal (nanodomains) to the channel. Our results demonstrate that the calcium domains of 5-HT3Rs do not overlap other calcium sources or their respective vesicle pools. 5-HT3Rs add a unique calcium source on ST afferents as part of multiple independent synaptic signaling mechanisms.

KW - 5-HTR

KW - Calcium domains

KW - Glutamate release

KW - NTS

KW - TRPV1

KW - Vesicle pools

UR - http://www.scopus.com/inward/record.url?scp=85069882605&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85069882605&partnerID=8YFLogxK

U2 - 10.1016/j.brainres.2019.146346

DO - 10.1016/j.brainres.2019.146346

M3 - Article

VL - 1721

JO - Brain Research

JF - Brain Research

SN - 0006-8993

M1 - 146346

ER -