2. Academic Validation
  3. Signal transduction pathways involved in dopamine D2 receptor-evoked emesis in the least shrew (Cryptotis parva)

Signal transduction pathways involved in dopamine D2 receptor-evoked emesis in the least shrew (Cryptotis parva)

  • Auton Neurosci. 2021 Jul;233:102807. doi: 10.1016/j.autneu.2021.102807.
Louiza Belkacemi 1,  Weixia Zhong 1,  Nissar A Darmani 2
Affiliations

Affiliations

  • 1 Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA 91766, USA.
  • 2 Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA 91766, USA. Electronic address: [email protected].
PMID: 33865060 DOI: 10.1016/j.autneu.2021.102807
Abstract

With its five receptor subtypes (D1-5), dopamine is implicated in a myriad of neurological illnesses. Dopamine D2 receptor-based agonist therapy evokes nausea and vomiting. The signaling mechanisms by which dopamine D2 receptors evoke vomiting remains unknown. Phosphatidylinositol 3-kinases (PI3K)- and protein kinase C (PKC)-related signaling cascades stimulate vomiting post-injection of various emetogens in emetically competent Animals. This study investigated potential mechanisms involved in dopamine D2 receptor-mediated vomiting using least shrews. We found that vomiting evoked by the selective dopamine D2 receptor agonist quinpirole (2 mg/kg, i.p.) was significantly suppressed by: i) a dopamine D2 preferring antagonist, sulpiride (s.c.); ii) a selective PI3K Inhibitor, LY294002 (i.p.); iii) a PKCαβII inhibitor, GF109203X (i.p.); and iv) a selective inhibitor of extracellular signal-regulated protein kinase1/2 (ERK1/2), U0126 (i.p.). Quinpirole-evoked c-fos immunofluorescence in the nucleus tractus solitarius (NTS) was suppressed by pretreatment with sulpiride (8 mg/kg, s.c.). Western blot analysis of shrew brainstem emetic loci protein lysates revealed a significant and time-dependent increase in phosphorylation of Akt (protein kinase B (PKB)) at Ser473 following a 30-min exposure to quinpirole (2 mg/kg, i.p.). Pretreatment with effective antiemetic doses of sulpiride, LY294002, GF109203X, or U0126 significantly reduced quinpirole-stimulated phosphorylation of emesis-associated proteins including p-85PI3K, mTOR (Ser2448/2481), PKCαβII (Thr638/641), ERK1/2 (Thr202/204), and Akt (Ser473). Our results substantiate the implication of PI3K/mTOR/Akt and PI3K/PKCαβII/ERK1/2/Akt signaling pathways in dopamine D2 receptor-mediated vomiting. Potential novel antiemetics targeting emetic proteins associated with these signaling cascades may offer enhanced potency and/or efficacy against emesis.

Keywords

Brainstem; Dopamine D(2) receptor; Emesis; Least shrew; PI3K/PKCαβII/ERK1/2/Akt; PI3K/mTOR/Akt.

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