Single channel properties of the 5-HT3 subtype of serotonin receptor in primary cultures of rodent hippocampus

doi:10.1016/0304-3940(94)90004-3

Neuroscience Letters

Volume 174, Issue 2, 20 June 1994, Pages 133-136

https://doi.org/10.1016/0304-3940(94)90004-3 Get rights and content

Abstract

Whole cell and outside-out patch clamp recordings were obtained from primary cultures of rat and mouse hippocampal neurons. Serotonin (5-HT) evoked short-latency fast inward currents in about 5% of neurons. These currents reversed near 0 mV, showed inward rectification, and were inhibited by the 5-HT₃ receptor antagonists ICS 205–930, ondansetron and tubocurare. 5-HT activated single channel currents in 14 of 24 membrane patches obtained from neurons which showed 5-HT₃-activated whole cell currents; mean amplitude of channel openings was 0.95 ± 0.09 pA at −100 mV. Chord conductances measured at −80 and −160 mV were 8.3 and 10.5 pS, respectively. 5-HT-induced unitary currents were blocked reversibly by tubocurare (1 μM), ICS 205–930 (30 mM) and ondansetron (100 nM). Thus, single-channel properties of 5-HT₃ receptors in hippocampal neurons are similar to those present in peripheral neurons and do not exhibit solely the sub-picosiemen conductance characteristic of the neuroblastoma and neuroblastoma-derived cloned 5-HT₃ receptor.

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Cited by (25)

Therapeutics of 5-HT<inf>3</inf> receptor antagonists: Current uses and future directions
2011, Pharmacology and Therapeutics
Citation Excerpt :
In contrast, other investigators found 5-HT3B subunit staining in the hippocampus (Monk et al., 2001; Reeves & Lummis, 2006). Relatively large single channel conductances have been recorded in hippocampal 5-HT3 receptors (Jones & Suprenant, 1994), which are similar to that obtained with recombinant 5-HT3A/B receptors. It remains to be determined whether the B subunit or perhaps a C or E subunit combines with the A subunit to produce larger single channel conductances in native hippocampal receptors than that observed in heterologously expressed A homomers.
The 5-Hydroxytryptamine₃ (5-HT₃) receptor is a member of the cys-loop family of ligand gated ion channels, of which the nicotinic acetylcholine receptor is the prototype. All other 5-HT receptors identified to date are metabotropic receptors. The 5-HT₃ receptor is present in the central and peripheral nervous systems, as well as a number of non-nervous tissues. As an ion channel that is permeable to the cations, Na⁺, K⁺, and Ca²⁺, the 5-HT₃ receptor mediates fast depolarizing responses in pre- and post-synaptic neurons. As such, 5-HT₃ receptor antagonists that are used clinically block afferent and efferent synaptic transmission. The most well established physiological roles of the 5-HT₃ receptor are to coordinate emesis and regulate gastrointestinal motility. Currently marketed 5-HT₃ receptor antagonists are indicated for the treatment of chemotherapy, radiation, and anesthesia-induced nausea and vomiting, as well as irritable bowel syndrome. Other therapeutic uses that have been explored include pain and drug addiction. The 5-HT₃ receptor is one of a number of receptors that play a role in mediating nausea and vomiting, and as such, 5-HT₃ receptor antagonists demonstrate the greatest anti-emetic efficacy when administered in combination with other drug classes.
The 5-HT<inf>3</inf> receptor - the relationship between structure and function
2009, Neuropharmacology
Citation Excerpt :
In contrast to the rodent 5-HT3A subunit, the expression of the 5-HT3B subunit in rodent hippocampus is controversial (see van Hooft and Yakel, 2003; Jensen et al., 2008). Despite evidence that rodent hippocampal neurones possess relatively high single channel conductance 5-HT3 receptors (Jones and Surprenant, 1994; reviewed by Fletcher and Barnes, 1998) which would be consistent with the expression of 5-HT3AB receptors (see Section 5), 5-HT3B subunit transcripts appear absent (van Hooft and Yakel, 2003; Dover and Barnes, unpublished observations). To add to the inconsistency, three independent studies using different antisera have identified 5-HT3B-like immunoreactivity in rat hippocampus that appear to be expressed by a similar pattern of neurones to those expressing 5-HT3A subunits (Monk et al., 2001; Reeves and Lummis, 2006; Doucet et al., 2007).
The 5-hydroxytryptamine type-3 (5-HT₃) receptor is a cation-selective ion channel of the Cys-loop superfamily. 5-HT₃ receptor activation in the central and peripheral nervous systems evokes neuronal excitation and neurotransmitter release. Here, we review the relationship between the structure and the function of the 5-HT₃ receptor. 5-HT3A and 5-HT3B subunits are well established components of 5-HT₃ receptors but additional HTR3C, HTR3D and HTR3E genes expand the potential for molecular diversity within the family. Studies upon the relationship between subunit structure and the ionic selectivity and single channel conductances of 5-HT₃ receptors have identified a novel domain (the intracellular MA-stretch) that contributes to ion permeation and selectivity. Conventional and unnatural amino acid mutagenesis of the extracellular domain of the receptor has revealed residues, within the principle (A–C) and complementary (D–F) loops, which are crucial to ligand binding. An area requiring much further investigation is the subunit composition of 5-HT₃ receptors that are endogenous to neurones, and their regional expression within the central nervous system. We conclude by describing recent studies that have identified numerous HTR3A and HTR3B gene polymorphisms that impact upon 5-HT₃ receptor function, or expression, and consider their relevance to (patho)physiology.
3B but which 3B? And that's just one of the questions: the heterogeneity of human 5-HT<inf>3</inf> receptors
2008, Trends in Pharmacological Sciences
The 5-hydroxytryptamine 3 (5-HT₃) receptor is expressed widely in the central and peripheral nervous systems, where it mediates or modulates a wide range of physiological processes. The receptor is targeted by drugs administered for nausea and/or emesis and irritable bowel syndrome and has been proposed as a potential drug target in various psychiatric disorders. The 5-HT₃ receptor is a pentameric ligand-gated ion channel and belongs to the Cys-loop receptor family. In contrast to the immense heterogeneity characterizing other Cys-loop receptors, native 5-HT₃ receptors historically have been considered a much more homogenous receptor population. However, the recent discovery of additional 5-HT₃ subunits and the dawning realization that central and peripheral 5-HT₃ receptor populations might comprise several subtypes characterized by distinct functional properties has emphasized the complexity of human 5-HT₃ receptor signaling. In this review potential implications of these findings and of the entirely new layer of interindividual diversity introduced to the 5-HT₃ receptor system by genetic variations will be outlined.
Targeted gene deletion of the 5-HT<inf>3A</inf> receptor subunit produces an anxiolytic phenotype in mice
2003, European Journal of Pharmacology
Anxiety disorders are the most common psychiatric disorders. Typical medications used to treat patients are benzodiazepines or antidepressants that target serotonin (5-HT) activity. The ionotropic 5-HT₃ receptor has emerged as a potential therapeutic target because selective antagonist compounds reduce anxiety in rodents, primates, and humans. 5-HT binds to the extracellular N-terminus of the 5-HT_3A receptor subunit, but receptor activation is also enhanced by distinct allosteric sites. It is not known if specific molecular subunits of the 5-HT₃ receptor modulate anxiety. To address this issue, we characterized anxiety-like behavior of mice with a targeted deletion of the 5-HT_3A receptor subunit gene in the light/dark box, elevated plus maze, and novelty interaction animal models of anxiety. 5-HT_3A null mice exhibited an anxiolytic behavioral phenotype that was highly correlated across behavioral measures. This evidence indicates that the 5-HT_3A molecular subunit influences anxiety-like behavior. Pharmacotherapy that targets specifically the 5-HT_3A receptor subunit may provide a novel treatment for anxiety disorders.
Cloned human and murine serotonin<inf>3A</inf> receptors expressed in human embryonic kidney 293 cells display different single-channel kinetics
2002, Neuroscience Letters
In the present study, well-resolved single-channel events of cloned human and murine homomeric 5-hydroxytryptamine type 3 (h5-HT_3A and m5-HT_3A) receptors, expressed in human embryonic kidney 293 cells, are reported for the first time. 5-HT (1 μM) applied in Ca²⁺- and Mg²⁺-free external solution to excised outside-out membrane patches induced non-rectifying single-channel inward currents. These currents were not observed in untransfected cells or in the presence of the antagonist ondansetron (1 μM). The mean single-channel conductance of the h5-HT_3A and m5-HT_3A receptors was 48±8 pS and 46±7 pS, the mean reversal potential was 10.3±1.8 mV and 4.7±5.3 mV, respectively. The analysis of single-channel open-times revealed for both h5-HT_3A and m5-HT_3A receptors only one type of open state, but different mean open-times (7.1±2.9 ms vs. 4.1±0.8 ms) indicating species-dependent gating mechanisms of 5-HT₃ receptors.
The pharmacological and functional characteristics of the serotonin 5- HT(3A) receptor are specifically modified by a 5-HT(3B) receptor subunit
1999, Journal of Biological Chemistry
While homomers containing 5-HT_3A subunits form functional ligand-gated serotonin (5-HT) receptors in heterologous expression systems (Jackson, M. B., and Yakel, J. L. (1995) Annu. Rev. Physiol. 57, 447–468; Lambert, J. J., Peters, J. A., and Hope, A. G. (1995) in Ligand-Voltage-Gated Ion Channels (North, R., ed) pp. 177–211, CRC Press, Inc., Boca Raton, FL), it has been proposed that native receptors may exist as heteromers (Fletcher, S., and Barnes, N. M. (1998) Trends Pharmacol. Sci. 19, 212–215). We report the cloning of a subunit 5-HT_3B with ∼44% amino acid identity to 5-HT_3A that specifically modified 5-HT_3Areceptor kinetics, voltage dependence, and pharmacology. Co-expression of 5-HT_3B with 5-HT_3A modified the duration of 5-HT₃ receptor agonist-induced responses, linearized the current-voltage relationship, increased agonist and antagonist affinity, and reduced cooperativity between subunits. Reverse transcriptase-polymerase chain reaction in situhybridization revealed co-localization of both 5-HT_3B and 5-HT_3A in a population of neurons in the amygdala, telencephalon, and entorhinal cortex. Furthermore, 5-HT_3Aand 5-HT_3B mRNAs were expressed in spleen and intestine. Our data suggest that 5-HT_3B might contribute to tissue-specific functional changes in 5-HT₃-mediated signaling and/or modulation.

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Single channel properties of the 5-HT3 subtype of serotonin receptor in primary cultures of rodent hippocampus

Abstract

Eur. J. Pharmacol.

Neuropharmacology

Trends Pharmacol. Sci.

Neuron

Neuron

Cell culture of neocortex and basal forebrain from postnatal rats

Rapid solution exchange using a piezoelectric translator

Axobits

5-HT3 receptors are membrane ion channels

Nature

5-hydroxytryptamine receptors of visceral primary afferent neurones on rabbit nodose ganglia

J. Physiol.

Functional properties of the cloned 5HT3-A receptor: comparison with native mouse receptors

J. Physiol.

Single channel properties of the 5-HT₃ subtype of serotonin receptor in primary cultures of rodent hippocampus

5-HT₃ receptors are membrane ion channels

Functional properties of the cloned 5HT₃-A receptor: comparison with native mouse receptors