The α1-adrenergic receptors in the amygdala regulate the induction of learned despair through protein kinase C-beta signaling

Shisui Fujita, Satomi Yoshida, Tohru Matsuki, Manoj Kumar Jaiswal, Kenjiro Seki

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Hyperactivity of amygdala is observed in patients with major depressive disorder. Although the role of α1-adrenoceptor in amygdala on fear memory has been well studied, the role of α1-adrenoceptor in amygdala on depression-like behaviors remains unclear. Therefore, we investigated the effect of α1A-adrenoreceptor in amygdala on despair behavior, evaluated by the immobility time during tail suspension test (TST), pharmacological intervention, and immunohistological methods. C57BL6/J mice given a bilateral intra-amygdala injection of artificial cerebrospinal fluid exhibited an increased duration of immobility in the latter half of both trials of TST with a 24-h interval, a phenomenon known as learned despair. Intra-amygdala injection of WB4101 (1.7 nmol/0.1 µl), an α1adrenoreceptor antagonist, but not propranolol (250 pmol/0.1 µl), a β-adrenoreceptor antagonist, blocked the induction of learned despair during TST. Immunostaining experiments revealed that ∼61-75% of α1A-adrenoreceptor-positive neurons were colocalized with GAD65/67 in amygdala, implying that the α1-adrenoceptors in amygdala may enormously regulate the GABA release. Protein kinase C-beta (PKCβ) was predominantly expressed in the α1A-adrenoreceptor-positive neurons in the BLA, whereas protein kinase C-epsilon (PKCϵ) was highly expressed with the α1A-adrenoreceptor in the Central nucleus of amygdala. Intra-amygdala injection of ruboxistaurin (10 pmol/0.1 µl), a PKCβ inhibitor, blocked the induction of learned despair during TST, whereas neither TAT-ϵV1-2 (500 ng/0.1 μl), a cell-permeant PKCϵ inhibitory peptide, nor HBDDE (50 pmol/0.1 µl), an inhibitor of PKCα and -γ, affected the duration of immobility during TST. These data suggest that the α1-adrenoreceptor in amygdala regulates the induction of learned despair via PKCβ.

Original languageEnglish
Pages (from-to)73-85
Number of pages13
JournalBehavioural Pharmacology
Volume32
Issue number1
DOIs
StatePublished - 1 Feb 2021

Keywords

  • GABAergic inhibition
  • basolateral amygdala
  • learned despair
  • protein kinase C-beta
  • α-adrenergic receptor

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