Activation of presynaptic 5-HT3 receptors facilitates glutamatergic synaptic inputs to area postrema neurons in rat brain slices

Makoto Funahashi, Yoshihiro Mitoh, R. Matsuo

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Abstract

Whole-cell voltage-clamp recordings were performed to investigate the serotonergic modulation of neurotransmitter release onto rat area postrema neurons in vitro. The bath application of serotonin (5-HT; 50 μM) or phenylbiguanide (PBA; 50 μM), a potent 5-HT3 receptor agonist, increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) or miniature EPSCs (mEPSCs) in 35 of 83 neurons (42%). These increases occurred in all electrophysiological cell classes. No cells exhibited a decrease in EPSC frequency. The majority of responding cells showed no inward currents during the application of serotonergic agonists (n = 34/35). However, the amplitude of MEPSCS was increased in 11/11 cells with 5-HT or 3/11 cells with PBA. 1CS-205,930, a potent 5-HT3 receptor antagonist, markedly suppressed the 5-HT-induced facilitation of SEPSCS (n = 5) or MEPSCS (n = 5). An increase in the frequency of MEPSCS after PBA exposure was found, even with media containing Cd2+ (50 μM) or zero Ca2+. MEPSCS and evoked EPSCs were completely blocked in media containing the non-NMDA ionotropic receptor antagonist, CNQX (10 μM), indicating that EPSCs were glutamate events. These results suggest that glutamate release is increased in the area postrema by presynaptic 5-HT3 receptor activation. Furthermore, we present evidence that 5-HT3 receptor activation may be able to directly release glutamate from terminals, bypassing a requirement for voltage-dependent calcium entry into terminals. Such a mechanism may contribute to the chemosensitive function of area postrema neurons.

Original languageEnglish
Pages (from-to)615-622
Number of pages8
JournalMethods and Findings in Experimental and Clinical Pharmacology
Volume26
Issue number8
DOIs
Publication statusPublished - Oct 2004

Fingerprint

Area Postrema
Receptors, Serotonin, 5-HT3
Neurons
Serotonin
Brain
Glutamic Acid
Serotonin 5-HT3 Receptor Agonists
6-Cyano-7-nitroquinoxaline-2,3-dione
Serotonin 5-HT3 Receptor Antagonists
Serotonin Receptor Agonists
Excitatory Postsynaptic Potentials
Baths
Neurotransmitter Agents
Calcium

Keywords

  • 5-HT receptor
  • Area postrema
  • Brain slice
  • Glutamatergic transmission
  • Presynaptic terminal
  • Whole cell recording

ASJC Scopus subject areas

  • Pharmacology (medical)
  • Pharmacology, Toxicology and Pharmaceutics(all)

Cite this

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title = "Activation of presynaptic 5-HT3 receptors facilitates glutamatergic synaptic inputs to area postrema neurons in rat brain slices",
abstract = "Whole-cell voltage-clamp recordings were performed to investigate the serotonergic modulation of neurotransmitter release onto rat area postrema neurons in vitro. The bath application of serotonin (5-HT; 50 μM) or phenylbiguanide (PBA; 50 μM), a potent 5-HT3 receptor agonist, increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) or miniature EPSCs (mEPSCs) in 35 of 83 neurons (42{\%}). These increases occurred in all electrophysiological cell classes. No cells exhibited a decrease in EPSC frequency. The majority of responding cells showed no inward currents during the application of serotonergic agonists (n = 34/35). However, the amplitude of MEPSCS was increased in 11/11 cells with 5-HT or 3/11 cells with PBA. 1CS-205,930, a potent 5-HT3 receptor antagonist, markedly suppressed the 5-HT-induced facilitation of SEPSCS (n = 5) or MEPSCS (n = 5). An increase in the frequency of MEPSCS after PBA exposure was found, even with media containing Cd2+ (50 μM) or zero Ca2+. MEPSCS and evoked EPSCs were completely blocked in media containing the non-NMDA ionotropic receptor antagonist, CNQX (10 μM), indicating that EPSCs were glutamate events. These results suggest that glutamate release is increased in the area postrema by presynaptic 5-HT3 receptor activation. Furthermore, we present evidence that 5-HT3 receptor activation may be able to directly release glutamate from terminals, bypassing a requirement for voltage-dependent calcium entry into terminals. Such a mechanism may contribute to the chemosensitive function of area postrema neurons.",
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AU - Funahashi, Makoto

AU - Mitoh, Yoshihiro

AU - Matsuo, R.

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AB - Whole-cell voltage-clamp recordings were performed to investigate the serotonergic modulation of neurotransmitter release onto rat area postrema neurons in vitro. The bath application of serotonin (5-HT; 50 μM) or phenylbiguanide (PBA; 50 μM), a potent 5-HT3 receptor agonist, increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) or miniature EPSCs (mEPSCs) in 35 of 83 neurons (42%). These increases occurred in all electrophysiological cell classes. No cells exhibited a decrease in EPSC frequency. The majority of responding cells showed no inward currents during the application of serotonergic agonists (n = 34/35). However, the amplitude of MEPSCS was increased in 11/11 cells with 5-HT or 3/11 cells with PBA. 1CS-205,930, a potent 5-HT3 receptor antagonist, markedly suppressed the 5-HT-induced facilitation of SEPSCS (n = 5) or MEPSCS (n = 5). An increase in the frequency of MEPSCS after PBA exposure was found, even with media containing Cd2+ (50 μM) or zero Ca2+. MEPSCS and evoked EPSCs were completely blocked in media containing the non-NMDA ionotropic receptor antagonist, CNQX (10 μM), indicating that EPSCs were glutamate events. These results suggest that glutamate release is increased in the area postrema by presynaptic 5-HT3 receptor activation. Furthermore, we present evidence that 5-HT3 receptor activation may be able to directly release glutamate from terminals, bypassing a requirement for voltage-dependent calcium entry into terminals. Such a mechanism may contribute to the chemosensitive function of area postrema neurons.

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KW - Whole cell recording

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