---
OA_place: publisher
_id: '7525'
abstract:
- lang: eng
  text: "The medial habenula (MHb) is an evolutionary conserved epithalamic structure
    important for the modulation of emotional memory. It is involved in regulation
    of anxiety, compulsive behavior, addiction (nicotinic and opioid), sexual and
    feeding behavior. MHb receives inputs from septal regions and projects exclusively
    to the interpeduncular nucleus (IPN). Distinct sub-regions of the septum project
    to different subnuclei of MHb: the bed nucleus of anterior commissure projects
    to dorsal MHb and the triangular septum projects to ventral MHb. Furthermore,
    the dorsal and ventral MHb project to the lateral and rostral/central IPN, respectively.
    Importantly, these projections have unique features of prominent co-release of
    different neurotransmitters and requirement of a peculiar type of calcium channel
    for release. In general, synaptic neurotransmission requires an activity-dependent
    influx of Ca2+ into the presynaptic terminal through voltage-gated calcium channels.
    The calcium channel family most commonly involved in neurotransmitter release
    comprises three members, P/Q-, N- and R-type with Cav2.1, Cav2.2 and Cav2.3 subunits,
    respectively. In contrast to most CNS synapses that mainly express Cav2.1 and/or
    Cav2.2, MHb terminals in the IPN exclusively express Cav2.3. In other parts of
    the brain, such as the hippocampus, Cav2.3 is mostly located to postsynaptic elements.
    This unusual presynaptic location of Cav2.3 in the MHb-IPN pathway implies unique
    mechanisms of glutamate release in this pathway. One potential example of such
    uniqueness is the facilitation of release by GABAB receptor (GBR) activation.
    Presynaptic GBRs usually inhibit the release of neurotransmitters by inhibiting
    presynaptic calcium channels. MHb shows the highest expression levels of GBR in
    the brain. GBRs comprise two subunits, GABAB1 (GB1) and GABAB2 (GB2), and are
    associated with auxiliary subunits, called potassium channel tetramerization domain
    containing proteins (KCTD) 8, 12, 12b and 16. Among these four subunits, KCTD12b
    is exclusively expressed in ventral MHb, and KCTD8 shows the strongest expression
    in the whole MHb among other brain regions, indicating that KCTD8 and KCTD12b
    may be involved in the unique mechanisms of neurotransmitter release mediated
    by Cav2.3 and regulated by GBRs in this pathway. \r\nIn the present study, we
    first verified that neurotransmission in both dorsal and ventral MHb-IPN pathways
    is mainly mediated by Cav2.3 using a selective blocker of R-type channels, SNX-482.
    We next found that baclofen, a GBR agonist, has facilitatory effects on release
    from ventral MHb terminal in rostral IPN, whereas it has inhibitory effects on
    release from dorsal MHb terminals in lateral IPN, indicating that KCTD12b expressed
    exclusively in ventral MHb may have a role in the facilitatory effects of GBR
    activation. In a heterologous expression system using HEK cells, we found that
    KCTD8 and KCTD12b but not KCTD12 directly bind with Cav2.3. Pre-embedding immunogold
    electron microscopy data show that Cav2.3 and KCTD12b are distributed most densely
    in presynaptic active zone in IPN with KCTD12b being present only in rostral/central
    but not lateral IPN, whereas GABAB, KCTD8 and KCTD12 are distributed most densely
    in perisynaptic sites with KCTD12 present more frequently in postsynaptic elements
    and only in rostral/central IPN. In freeze-fracture replica labelling, Cav2.3,
    KCTD8 and KCTD12b are co-localized with each other in the same active zone indicating
    that they may form complexes regulating vesicle release in rostral IPN. \r\nOn
    electrophysiological studies of wild type (WT) mice, we found that paired-pulse
    ratio in rostral IPN of KCTD12b knock-out (KO) mice is lower than those of WT
    and KCTD8 KO mice. Consistent with this finding, in mean variance analysis, release
    probability in rostral IPN of KCTD12b KO mice is higher than that of WT and KCTD8
    KO mice. Although paired-pulse ratios are not different between WT and KCTD8 KO
    mice, the mean variance analysis revealed significantly lower release probability
    in rostral IPN of KCTD8 KO than WT mice. These results demonstrate bidirectional
    regulation of Cav2.3-mediated release by KCTD8 and KCTD12b without GBR activation
    in rostral IPN. Finally, we examined the baclofen effects in rostral IPN of KCTD8
    and KCTD12b KO mice, and found the facilitation of release remained in both KO
    mice, indicating that the peculiar effects of the GBR activation in this pathway
    do not depend on the selective expression of these KCTD subunits in ventral MHb.
    However, we found that presynaptic potentiation of evoked EPSC amplitude by baclofen
    falls to baseline after washout faster in KCTD12b KO mice than WT, KCTD8 KO and
    KCTD8/12b double KO mice. This result indicates that KCTD12b is involved in sustained
    potentiation of vesicle release by GBR activation, whereas KCTD8 is involved in
    its termination in the absence of KCTD12b. Consistent with these functional findings,
    replica labelling revealed an increase in density of KCTD8, but not Cav2.3 or
    GBR at active zone in rostral IPN of KCTD12b KO mice compared with that of WT
    mice, suggesting that increased association of KCTD8 with Cav2.3 facilitates the
    release probability and termination of the GBR effect in the absence of KCTD12b.\r\nIn
    summary, our study provided new insights into the physiological roles of presynaptic
    Cav2.3, GBRs and their auxiliary subunits KCTDs at an evolutionary conserved neuronal
    circuit. Future studies will be required to identify the exact molecular mechanism
    underlying the GBR-mediated presynaptic potentiation on ventral MHb terminals.
    It remains to be determined whether the prominent presence of presynaptic KCTDs
    at active zone could exert similar neuromodulatory functions in different pathways
    of the brain.\r\n"
acknowledged_ssus:
- _id: EM-Fac
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Pradeep
  full_name: Bhandari, Pradeep
  id: 45EDD1BC-F248-11E8-B48F-1D18A9856A87
  last_name: Bhandari
  orcid: 0000-0003-0863-4481
citation:
  ama: Bhandari P. Localization and functional role of Cav2.3 in the medial habenula
    to interpeduncular nucleus pathway. 2020. doi:<a href="https://doi.org/10.15479/AT:ISTA:7525">10.15479/AT:ISTA:7525</a>
  apa: Bhandari, P. (2020). <i>Localization and functional role of Cav2.3 in the medial
    habenula to interpeduncular nucleus pathway</i>. Institute of Science and Technology
    Austria. <a href="https://doi.org/10.15479/AT:ISTA:7525">https://doi.org/10.15479/AT:ISTA:7525</a>
  chicago: Bhandari, Pradeep. “Localization and Functional Role of Cav2.3 in the Medial
    Habenula to Interpeduncular Nucleus Pathway.” Institute of Science and Technology
    Austria, 2020. <a href="https://doi.org/10.15479/AT:ISTA:7525">https://doi.org/10.15479/AT:ISTA:7525</a>.
  ieee: P. Bhandari, “Localization and functional role of Cav2.3 in the medial habenula
    to interpeduncular nucleus pathway,” Institute of Science and Technology Austria,
    2020.
  ista: Bhandari P. 2020. Localization and functional role of Cav2.3 in the medial
    habenula to interpeduncular nucleus pathway. Institute of Science and Technology
    Austria.
  mla: Bhandari, Pradeep. <i>Localization and Functional Role of Cav2.3 in the Medial
    Habenula to Interpeduncular Nucleus Pathway</i>. Institute of Science and Technology
    Austria, 2020, doi:<a href="https://doi.org/10.15479/AT:ISTA:7525">10.15479/AT:ISTA:7525</a>.
  short: P. Bhandari, Localization and Functional Role of Cav2.3 in the Medial Habenula
    to Interpeduncular Nucleus Pathway, Institute of Science and Technology Austria,
    2020.
corr_author: '1'
date_created: 2020-02-26T10:56:37Z
date_published: 2020-02-28T00:00:00Z
date_updated: 2026-04-08T07:27:27Z
day: '28'
ddc:
- '570'
degree_awarded: PhD
department:
- _id: RySh
doi: 10.15479/AT:ISTA:7525
file:
- access_level: open_access
  checksum: 4589234fdb12b4ad72273b311723a7b4
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  date_created: 2020-02-28T08:37:53Z
  date_updated: 2021-03-01T23:30:04Z
  embargo: 2021-02-28
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  file_size: 9646346
  relation: main_file
  title: Localization and functional role of Cav2.3 in the medial habenula to interpeduncular
    nucleus pathway
- access_level: closed
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  creator: pbhandari
  date_created: 2020-02-28T08:47:14Z
  date_updated: 2021-03-01T23:30:04Z
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  title: Localization and functional role of Cav2.3 in the medial habenula to interpeduncular
    nucleus pathway
file_date_updated: 2021-03-01T23:30:04Z
has_accepted_license: '1'
keyword:
- Cav2.3
- medial habenula (MHb)
- interpeduncular nucleus (IPN)
language:
- iso: eng
month: '02'
oa: 1
oa_version: Published Version
page: '79'
publication_identifier:
  issn:
  - 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
status: public
supervisor:
- first_name: Ryuichi
  full_name: Shigemoto, Ryuichi
  id: 499F3ABC-F248-11E8-B48F-1D18A9856A87
  last_name: Shigemoto
  orcid: 0000-0001-8761-9444
title: Localization and functional role of Cav2.3 in the medial habenula to interpeduncular
  nucleus pathway
type: dissertation
user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd
year: '2020'
...