Abstract
Estrogen modulates NMDA receptors function in the brain. It increases both dendritic spine density and synapse number in the hippocampus, an effect that can be blocked by NMDA antagonist. In this study, we investigated the effect of 17β‐estradiol and progesterone treatment on NMDA receptors in ovariectomized rats. Two different doses were used for 10 weeks. Receptor autoradiography was done on brain sections using [3H] MK‐801 as a ligand. Our results showed a significant increase in [3H] MK‐801 binding in the dentate gyrus, CA3 and CA4 areas of the hippocampus of ovariectomized compared to sham operated rats. In addition, we observed similar changes in CA1. 17β‐estradiol treatment in both doses reduced the binding back to the normal level while progesterone treatment did not show any effect. Spatial reference memory was tested on Morris water maze task. Ovariectomy severely impaired spatial reference memory. Estradiol but not progesterone treatment significantly improved the memory performance of the ovariectomized rats. Low dose treatment showed better learning than high dose estrogen treatment. The decrease in the antagonist sites by estradiol treatment could result in an increase in the sensitivity of the hippocampus to the excitatory stimulation by glutamate system and hence the effect of estradiol on learning and memory. The changes of NMDA receptors in the hippocampus support the concept that estrogen‐enhancing effect on spatial reference memory could be through the enhancing of NMDA function.
Keywords: ovariectomy, estradiol, progesterone, reference memory, MK‐801, NMDA
References
- 1. Schneider L.S., Farlow M., Combined tacrine and estrogen replacement therapy in patients with Alzheimer's disease, Ann. N. Y. Acad. Sci., 826: 317–322, 1997. [DOI] [PubMed] [Google Scholar]
- 2. Simpkins J.W., Green P.S., Gridley K.E., Singh M., de Fiebre N.C., Rajakumar G., Role of estrogen replacement therapy in memory enhancement and the prevention of neu‐ronal loss associated with Alzheimer's disease, Am. J. Med. 103: 19S–25S, 1997. [DOI] [PubMed] [Google Scholar]
- 3. Yagyu K., Kitagawa K., Wu B., Zhang N.Y., Irie T., Hattori N., Inagaki C., Protective effects of estradiol against amyloid beta protein‐induced inhibition of neuronal Cl(‐)‐ATPase activity, Neuropharmacol., 43: 1297–1304, 2002. [DOI] [PubMed] [Google Scholar]
- 4. Sawada H., Ibi M., Kihara T., Urushitani M., Akaike A., Shimohama S., Estradiol protects mesencephalic dopamin‐ergic neurons from oxidative stress‐induced neuronal death, J. Neurosci. Res., 54: 707–719, 1998. [DOI] [PubMed] [Google Scholar]
- 5. Chen J., Adachi N., Liu K., Arai T., The effects of 17beta‐estradiol on ischemia‐induced neuronal damage in the gerbil hippocampus, Neuroscience, 87: 817–22, 1998. [DOI] [PubMed] [Google Scholar]
- 6. Garcia‐Segura L.M., Naftolin F., Hutchison J.B., Azcoitia I., Chowen J.A., Role of astroglia in estrogen regulation of synaptic plasticity and brain repair, J. Neurobiol., 40: 574–84, 1999. [PubMed] [Google Scholar]
- 7. Gould E., Woolley C.S., Frankfurt M., McEwen B.S., Gonadal steroids regulate dendritic spine density in hippocampal pyramidal cells in adulthood, J. Neurosci., 10: 1286–1291, 1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. Woolley C.S., McEwen B.S., Roles of estradiol and progesterone in regulation of hippocampal dendritic spine density during the estrous cycle in the rat, J. Comp. Neurol., 336: 293–306, 1993. [DOI] [PubMed] [Google Scholar]
- 9. Woolley C.S., Weiland N.G., McEwen B.S., Schwartzkroin P.A., Estradiol increases the sensitivity of hippocampal CA1 pyramidal cells to NMDA receptor‐mediated synaptic input: correlation with dendritic spine density, J. Neurosci., 17: 1848–59, 1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10. Weiland N.G., Estradiol selectively regulates agonist binding sites on the N‐methyl‐D‐aspartate receptor complex in the CA1 region of the hippocampus, Endocrinology, 131: 662–668, 1992. [DOI] [PubMed] [Google Scholar]
- 11. Gazzaley A.H., Weiland N.G., McEwen B.S., Morrison J.H., Differential regulation of NMDAR1 mRNA and protein by estradiol in the rat hippocampus, J. Neurosci., 16: 6830–6838, 1996. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Collingridge G., Synaptic plasticity. The role of NMDA receptors in learning and memory, Nature, 330: 604–605, 1987. [DOI] [PubMed] [Google Scholar]
- 13. Nicolle M.M., Bizon J.L., Gallagher M., In vitro autoradiography of ionotropic glutamate receptors in hippocampus and striatum of aged Long‐Evans rats: relationship to spatial learning, Neuroscience, 74: 741–756, 1996. [DOI] [PubMed] [Google Scholar]
- 14. Collingridge G.L., The Sharpey‐Schafer Prize Lecture. The mechanism of induction of NMDA receptor‐dependent long‐term potentiation in the hippocampus, Exp. Physiol. 77: 771–797, 1992. [DOI] [PubMed] [Google Scholar]
- 15. Watkins J.C., Evans R.H., Excitatory amino acid transmitters, Annu Rev. Pharmacol. Toxicol., 21: 165–204, 1981. [DOI] [PubMed] [Google Scholar]
- 16. Wroblewski J.T., Danysz W., Modulation of glutamate receptors: molecular mechanisms and functional implications, Annu. Rev. Pharmacol. Toxicol., 29: 441–474, 1989. [DOI] [PubMed] [Google Scholar]
- 17. Gasic G.P., Hollmann M., Molecular neurobiology of glutamate receptors, Annu. Rev. Physiol., 54: 507–536, 1992. [DOI] [PubMed] [Google Scholar]
- 18. Choi D.W., Glutamate neurotoxicity and diseases of the nervous system, Neuron, 1: 623–634, 1988. [DOI] [PubMed] [Google Scholar]
- 19. Meldrum B., Garthwaite J., Excitatory amino acid neurotoxicity and neurodegenerative disease, Trends Pharmacol. Sci., 11: 379–387, 1990. [DOI] [PubMed] [Google Scholar]
- 20. Sherwin B.B., Estrogen effects on cognition in menopausal women, Neurology, 48: S21–S26, 1997. [DOI] [PubMed] [Google Scholar]
- 21. McEwen B.S., Gould E., Orchinik M., Weiland N.G., Woolley C.S., Oestrogens and the structural and functional plasticity of neurons: implications for memory, ageing and neurodegenerative processes, Ciba Found. Symp. 191: 52–66; discussion 66–73, 1995. [DOI] [PubMed] [Google Scholar]
- 22. Duka T., Tasker R., McGowan J.F., The effects of 3‐week estrogen hormone replacement on cognition in elderly healthy females, Psychopharmacol. (Berl.), 149: 129–139, 2000. [DOI] [PubMed] [Google Scholar]
- 23. LeBlanc E.S., Janowsky J., Chan B.K., Nelson H.D., Hormone replacement therapy and cognition: systematic review and meta‐analysis, JAMA, 285: 1489–1499, 2001. [DOI] [PubMed] [Google Scholar]
- 24. Hogervorst E., Williams J., Budge M., Riedel W., Jolles J., The nature of the effect of female gonadal hormone replacement therapy on cognitive function in post‐menopausal women: a meta‐analysis, Neuroscience, 101: 485–512, 2000. [DOI] [PubMed] [Google Scholar]
- 25. Fader A.J., Johnson P.E., Dohanich G.P., Estrogen improves working but not reference memory and prevents amnestic effects of scopolamine of a radial‐arm maze, Pharmacol. Biochem. Behav., 62: 711–717, 1999. [DOI] [PubMed] [Google Scholar]
- 26. Gibbs R. B., Estrogen replacement enhances acquisition of a spatial memory task and reduces deficits associated with hippocampal muscarinic receptor inhibition, Horm. Behav., 36: 222–233, 1999. [DOI] [PubMed] [Google Scholar]
- 27. Dohanich G.P., Fader A.J., Javorsky D.J., Estrogen and estrogen‐progesterone treatments counteract the effect of scopolamine on reinforced T‐maze alternation in female rats, Behav. Neurosci., 108: 988–992, 1994. [DOI] [PubMed] [Google Scholar]
- 28. Singh M., Meyer E.M., Millard W.J., Simpkins J.W., Ovarian steroid deprivation results in a reversible learning impairment and compromised cholinergic function in female Sprague‐Dawley rats, Brain Res., 644: 305–312, 1994. [DOI] [PubMed] [Google Scholar]
- 29. Galea L.A., Wide J.K., Paine T.A., Holmes M.M., Ormerod B.K., Floresco S.B., High levels of estradiol disrupt conditioned place preference learning, stimulus response learning and reference memory but have limited effects on working memory, Behav. Brain Res., 126: 115–126, 2001. [DOI] [PubMed] [Google Scholar]
- 30. Morris R.G.M., Spatial localization does not require the presence of local cues, Learn. Motiv., 12: 239–260, 1981. [Google Scholar]
- 31. Liljequist R., Henriksson B.G., Latif N., Pham T., Winblad B., Mohammed A.H., Subchronic MK‐801 treatment to juvenile rats attenuates environmental effects on adult spatial learning, Behav. Brain Res., 56: 107–114, 1993. [DOI] [PubMed] [Google Scholar]
- 32. Clark A.S., Magnusson K.R., Cotman C.W., In vitro autoradiography of hippocampal excitatory amino acid binding in aged Fischer 344 rats: relationship to performance on the Morris water maze, Behav. Neurosci., 106: 324–335, 1992. [DOI] [PubMed] [Google Scholar]
- 33. Loo P., Braunwalder A., Lehmann J., Williams M., Radioligand binding to central phencyclidine recognition sites is dependent on excitatory amino acid receptor agonists, Eur. J. Pharmacol., 123: 467–468, 1986. [DOI] [PubMed] [Google Scholar]
- 34. Woolley C.S., McEwen B.S., Estradiol mediates fluctuation in hippocampal synapse density during the estrous cycle in the adult rat, J. Neurosci., 12: 2549–2554, 1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35. Woolley C.S., McEwen B.S., Estradiol regulates hippocampal dendritic spine density via an N‐methyl‐D‐aspartate receptor‐dependent mechanism, J. Neurosci., 14: 7680–7687, 1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36. Frick K.M., Fernandez S.M., Bulinski S.C., Estrogen replacement improves spatial reference memory and increases hippocampal synaptophysin in aged female mice, Neuroscience, 115: 547–558, 2002. [DOI] [PubMed] [Google Scholar]
- 37. Wilson I.A., Puolivali J., Heikkinen T., Riekkinen P. Jr., Estrogen and NMDA receptor antagonism: effects upon reference and working memory, Eur. J. Pharmacol., 381: 93–99, 1999. [DOI] [PubMed] [Google Scholar]
- 38. El‐Bakri N.K., Adem A., Suliman I.A., Mulugeta E., Karlsson E., Lindgren J.U., Winblad B., Islam A., Estrogen and progesterone treatment: effects on muscarinic M(4) receptor subtype in the rat brain, Brain Res., 948: 131–137, 2002. [DOI] [PubMed] [Google Scholar]
- 39. Packard M.G., Teather L.A., Posttraining estradiol injections enhance memory in ovariectomized rats: cholinergic blockade and synergism, Neurobiol. Learn Mem., 68 172–88, 1997. [DOI] [PubMed] [Google Scholar]
- 40. Luine V.N., Richards S.T., Wu V.Y., Beck K.D., Estradiol enhances learning and memory in a spatial memory task and effects levels of monoaminergic neurotransmitters, Horm. Behav., 34: 149–162, 1998. [DOI] [PubMed] [Google Scholar]
- 41. Warner M., Nilsson S., Gustafsson J.A., The estrogen receptor family, Curr. Opin. Obstet. Gynecol., 11: 249–254, 1999. [DOI] [PubMed] [Google Scholar]
- 42. Shughrue P., Scrimo P., Lane M., Askew R., Merchenthaler I., The distribution of estrogen receptor‐beta mRNA in forebrain regions of the estrogen receptor‐alpha knockout mouse, Endocrinology, 138: 5649–5652, 1997. [DOI] [PubMed] [Google Scholar]
- 43. Daniel J.M., Dohanich G.P., Acetylcholine mediates the estrogen‐induced increase in NMDA receptor binding in CA1 of the hippocampus and the associated improvement in working memory, J. Neurosci., 21: 6949–6956, 2001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 44. Nilsen J., Chen S., Brinton R.D., Dual action of estrogen on glutamate‐induced calcium signaling: mechanisms requiring interaction between estrogen receptors and src/mitogen activated protein kinase pathway, Brain Res., 930: 216–234, 2002. [DOI] [PubMed] [Google Scholar]
