title: Estradiol-induced object recognition memory consolidation is dependent on activation of mTOR signaling in the dorsal hippocampus.
abstract: The mammalian target of rapamycin (mTOR) signaling pathway is an important regulator of protein synthesis and is essential for various forms of hippocampal memory. Here, we asked whether the enhancement of object recognition memory consolidation produced by dorsal hippocampal infusion of 17β-estradiol (E(2)) is dependent on mTOR signaling in the dorsal hippocampus, and whether E(2)-induced mTOR signaling is dependent on dorsal hippocampal phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) activation. We first demonstrated that the enhancement of object recognition induced by E(2) was blocked by dorsal hippocampal inhibition of ERK, PI3K, or mTOR activation. We then showed that an increase in dorsal hippocampal ERK phosphorylation 5 min after intracerebroventricular (ICV) E(2) infusion was also blocked by dorsal hippocampal infusion of the three cell signaling inhibitors. Next, we found that ICV infusion of E(2) increased phosphorylation of the downstream mTOR targets S6K (Thr-421) and 4E-BP1 in the dorsal hippocampus 5 min after infusion, and that this phosphorylation was blocked by dorsal hippocampal infusion of inhibitors of ERK, PI3K, and mTOR. Collectively, these data demonstrate for the first time that activation of the dorsal hippocampal mTOR signaling pathway is necessary for E(2) to enhance object recognition memory consolidation and that E(2)-induced mTOR activation is dependent on upstream activation of ERK and PI3K signaling.
authors: Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
authors: Ashley M
authors: AM
authors: Fortress
authors: Lu
authors: L
authors: Fan
authors: Patrick T
authors: PT
authors: Orr
authors: Zaorui
authors: Z
authors: Zhao
authors: Karyn M
authors: KM
authors: Frick
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000187:drug effects*; D007276:Injections, Intraventricular; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008568:Memory / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D010052:Ovariectomy; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D021641:Recognition, Psychology / Q000187:drug effects*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects*
chemical_list: D002070:Butadienes; D002867:Chromones; D004958:Estradiol; D004965:Estrogen Antagonists; D019950:Mitogen-Activated Protein Kinase 1; D009025:Morpholines; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C546843:mTOR protein, mouse; C512964:Rps6ka1 protein, mouse