Cerebrospinal fluid cortisol and progesterone profiles and outcomes prognostication after severe traumatic brain injury

Journal of Neurotrauma

Volumn 31, Issue 8, 2014, Pages 699-712

  Santarsieri, Martina ^a   Niyonkuru, Christian ^a   Mccullough, Emily H ^a   Dobos, Julie A ^a   Dixon, C Edward ^a,b   Berga, Sarah L ^c   Wagner, Amy K ^a,b  

^a UNIVERSITY OF PITTSBURGH SCHOOL OF MEDICINE   (United States)

^b UNIVERSITY OF PITTSBURGH   (United States)

^c WAKE FOREST SCHOOL OF MEDICINE   (United States)

Author keywords

cortisol; group based trajectory analysis; outcome; progesterone; traumatic brain injury

Indexed keywords

HYDROCORTISONE; PROGESTERONE;

ADOLESCENT; ADULT; AGED; ANALYSIS; ARTICLE; BLOOD BRAIN BARRIER; CEREBROSPINAL FLUID; CONTROLLED STUDY; FEMALE; GLASGOW OUTCOME SCALE; HORMONE METABOLISM; HORMONE TRANSPORT; HUMAN; MAJOR CLINICAL STUDY; MALE; PROGNOSIS; TRAJECTORY ANALYSIS; TRAUMATIC BRAIN INJURY;

ADOLESCENT; ADULT; AGED; BIOLOGICAL MARKERS; BRAIN INJURIES; ENZYME-LINKED IMMUNOSORBENT ASSAY; FEMALE; GLASGOW COMA SCALE; GLASGOW OUTCOME SCALE; HUMANS; HYDROCORTISONE; MALE; MIDDLE AGED; PROGESTERONE; PROGNOSIS; RADIOIMMUNOASSAY; RECOVERY OF FUNCTION; YOUNG ADULT;

EID: 84897402997     PISSN: 08977151     EISSN: 15579042     Source Type: Journal    
DOI: 10.1089/neu.2013.3177     Document Type: Article

References (89)

1. Roof, R.L., Duvdevani, R., and Stein, D.G. (1992). Progesterone treatment attenuates brain edema following contusion injury in male and female rats. Restor. Neurol. Neurosci. 4, 425-427
2. Roof, R.L., Duvdevani, R., and Stein, D. G. (1993). Gender influences outcome of brain injury: Progesterone plays a protective role. Brain Res. 607, 333-336
3. Schumacher, M., Akwa, Y., Guennoun, R., Robert, F., Labombarda, F., Desarnaud, F., Robel, P., De Nicola, A. F., and Baulieu, E.E. (2000). Steroid synthesis and metabolism in the nervous system: Trophic and protective effects. J. Neurocytol. 29, 307-326
4. Brinton, R.D., Thompson, R.F., Foy, M.R., Baudry, M., Wang, J., Finch, C.E., Morgan, T.E., Pike, C.J., Mack, W.J., Stanczyk, F.Z., and Nilsen, J. (2008). Progesterone receptors: Form and function in brain. Front Neuroendocrinol. 29, 313-339
5. Meffre, D., Labombarda, F., Delespierre, B., Chastre, A., De Nicola, A.F., Stein, D.G., Schumacher, M., and Guennoun, R. (2013). Distribution of membrane progesterone receptor alpha in the male mouse and rat brain and its regulation after traumatic brain injury. Neuroscience 231, 111-124
6. Sayeed, I., and Stein, D.G. (2009). Progesterone as a neuroprotective factor in traumatic and ischemic brain injury. Prog. Brain Res. 175, 219-237
7. Stein, D.G., and Wright, D.W. (2010). Progesterone in the clinical treatment of acute traumatic brain injury. Expert Opin. Investig. Drugs 19, 847-857
8. Stein, D.G. (2011). Is Progesterone a worthy candidate as a novel therapy for traumatic brain injury?. Dialogues Clin. Neurosci. 13, 352-359
9. Wright, D.W., Kellermann, A.L., Hertzberg, V.S., Clark, P.L., Frankel, M., Goldstein, F.C., Salomone, J.P., Dent, L.L., Harris, O.A., Ander, D.S., Lowery, D.W., Patel, M.M., Denson, D.D., Gordon, A.B., Wald, M.M., Gupta, S., Hoffman, S.W., and Stein, D.G. (2007). ProTECT: A randomized clinical trial of progesterone for acute traumatic brain injury. Ann. Emerg. Med. 49, 391-402
10. Djebaili, M., Hoffman, S.W., and Stein, D.G. (2004). Allopregnanolone and progesterone decrease cell death and cognitive deficits after a contusion of the rat pre-frontal cortex. Neuroscience 123, 349-359
11. He, J., Hoffman, S.W., and Stein, D.G. (2004). Allopregnanolone, a progesterone metabolite, enhances behavioral recovery and decreases neuronal loss after traumatic brain injury. Restor. Neurol. Neurosci. 22, 19-31
12. Cooke, P.S., Nanjappa, M.K., Yang, Z., and Wang, K.K. (2013). Therapeutic effects of progesterone and its metabolites in traumatic brain injury may involve non-classical signaling mechanisms. Front. Neurosci. 7, 108
13. Xiao, G., Wei, J., Yan, W., Wang, W., and Lu, Z. (2008). Improved outcomes from the administration of progesterone for patients with acute severe traumatic brain injury: A randomized controlled trial. Crit. Care. 12, R61
14. Bracken, M.B., Shepard, M.J., Collins, W.F., Holford, T.R., Young, W., Baskin, D.S., Eisenberg, H.M., Flamm, E., Leo-Summers, L., Maroon, J., et al. (1990). A randomized controlled trial of methylprednisolone or naloxone in the treatment of acute spinal cord injury. Results of the Second National Acute Spinal Cord Injury Study N. Eng. J. Med. 322, 1405-1411
15. Bracken, M.B., Shepard, M.J., Collins, W.F. Jr., Holford, T.R., Baskin, D.S., Eisenberg, H.M., Flamm, E., Leo-Summers, L., Maroon, J.C., Marshall, L.F., et al. (1992). Methylprednisolone or naloxone treatment after acute spinal cord injury: 1-year follow-up data. Results of the Second National Acute Spinal Cord Injury Study. J Neurosurg. 76, 23-31
16. Bracken, M.B., Shepard, M.J., Holford, T.R., Leo-Summers, L., Aldrich, E.F., Fazl, M., Fehlings, M., Herr, D.L., Hitchon, P.W., Marshall, L.F., Nockels, R.P., Pascale, V., Perot, P.L. Jr., Piepmeier, J., Sonntag, V.K., Wagner, F., Wilberger, J.E., Winn, H.R., and Young W. (1997). Administration of methylprednisolone for 24 or 48 hours or tirilazad mesylate for 48 hours in the treatment of acute spinal cord injury. Results of the Third National Acute Spinal Cord Injury Randomized Controlled Trial. National Acute Spinal Cord Injury Study. JAMA 277, 1597-1604
17. Faupel, G., Reulen, H. J., Müller, D., and Schürmann, K. (1976). Double-blind study on the effects of steroids on severe closed head injury, in: Dynamics of Brain Edema. M.M. Pappius, and W. Feindel (eds). Springer-Verlag: Berlin, pps. 337-343
18. Beauchamp, K., Mutlak, H., Smith, W.R., Shohami, E., and Stahel, P.F. (2008). Pharmacology of traumatic brain injury: Where is the ''golden bullet''?. Mol. Med. 14, 731-740
19. Alderson, P., and Roberts, I. (2005). Corticosteroids for acute traumatic brain injury. Cochrane Database Sys. Rev. 1, CD000196
20. Galicich, J.H., and French, L.A. (1961). Use of dexamethasone in the treatment of cerebral edema resulting from brain tumors and brain surgery. Am. Pract. Dig. Treat. 12, 169-174
21. Lamontagne, F., Quiroz Martinez, H., Adhikari, N.K., Cook, D.J., Koo, K.K., Lauzier, F., Turgeon, A.F., Kho, M.E., Burns, K.E., Chant, C., Fowler, R., Douglas, I., Poulin, Y., Choong, K., Ferguson, N.D, and Meade, M.O. (2013). Corticosteroid use in the intensive care unit: A survey of intensivists. Can. J. Anaesth. 60, 652-659
22. Roberts, I., Yates, D., Sandercock, P., Farrell, B., Wasserberg, J., Lomas, G., Cottingham, R., Svoboda, P., Brayley, N., Mazairac, G., Laloë, V., Mun̈oz-Sánchez, A., Arango, M., Hartzenberg, B., Khamis, H., Yutthakasemsunt, S., Komolafe, E., Olldashi, F., Yadav, Y., Murillo-Cabezas, F., Shakur, H., Edwards, P., and CRASH trial collaborators. (2004). Effect of intravenous corticosteroids on death within 14 days in 10008 adults with clinically significant head injury (MRC CRASH trial): Randomized placebo-controlled trial. Lancet 364, 1321-1328
23. Schumacher, M., Hussain, R., Gago, N., Oudinet, J.P., Mattern, C., and Ghoumari, A.M. (2012). Progesterone synthesis in the nervous system: Implications for myelination and myelin repair. Front. Neurosci. 6, 10
24. Baulieu, E.E., Robel, P., and Schumacher, M. (2001). Neurosteroids: Beginning of the story. Int. Rev. Neurobiol. 46, 1-32
25. Heffelfinger, A.K., and Newcomer, J.W. (2001). Glucocorticoid effects on memory function over the human life span. Dev. Psychopathol. 13, 491-513
26. De Kloet, E.R. (2004). Hormones and the stressed brain. Ann. N. Y. Acad. Sci. 1018, 1-15
27. Lupien, S.J., Maheu, F., Tu, M., Fiocco, A., and Schramek, T.E. (2007). The effects of stress and stress hormones on human cognition: Implications for the field of brain and cognition. Brain Cogn. 65, 209-237
28. Swaab, D.F., Bao, A.M., and Lucassen, P.J. (2005). The stress system in the human brain in depression and neurodegeneration. Ageing Res. Rev. 4, 141-194
29. Kling, S.R., Manna, P.R., Ishii, T., Syapin, P.J., Ginsberg, S.D., Wilson, K., Walsh, L.P., Parker, K.L., Stocco, D.M., Smith, R.G., and Lamb, D.J. (2002). An essential component in steroid synthesis, the steroidogenic acute regulatory protein, is expressed in discrete regions of the brain. J. Neurosci. 22, 10613-10620
30. Yu, L., Romero, D.G., Gomez-Sanchez, C.E., and Gomez-Sanchez, E.P. (2002). Steroidogenic enzyme gene expression in the human brain. Mol. Cell. Endocrinol. 190, 9-17
31. Stoffel-Wagner, B. (2003). Neurosteroid biosynthesis in the human brain and its clinical implications. Ann. N.Y. Acad. Sci. 1007, 64-78
32. Pluchino, N., Santoro, A., Casarosa, E., Wenger, J.M., Genazzani, A.D., Petignat, P., and Genazzani, A.R. (2013). Advances in neurosteroids: Role in clinical practice. Climacteric 16, Suppl 1, 8-17
33. Wagner, A.K., McCullough, E.H., Niyonkuru, C., Ozawa, H., Loucks, T., Dobos, J.A., Brett, C.A., Santarsieri, M., Dixon, C.E., Berga, S., and Fabio, A. (2011). Acute serum hormone levels: Characterization and prognosis after severe traumatic brain injury. J. Neurotrauma 28, 871-888
34. Garringer, J.A., Niyonkuru, C., McCullough, E.H., Loucks, T., Dixon, C.E., Conley, Y.P., Berga, S., and Wagner, A.K. (2013). Impact of aromatase genetic variation on hormone levels and global outcome after severe TBI. J. Neurotrauma 30, 1415-1425
35. Brain Trauma Foundation, American Association of Neurological Surgeons, and Congress of Neurological Surgeons. (2007). Guidelines for the management of severe traumatic brain injury. J. Neurotrauma 24, Suppl 1, S1-S106
36. Zafonte, R., Friedewald, W.T., Lee, S.M., Levin, B., Diaz-Arrastia, R., Ansel, B., Eisenberg, H., Timmons, S.D., Temkin, N., Novack, T., Ricker, J., Merchant, R., and Jallo, J. (2009). The citicoline brain injury treatment (COBRIT) trial: Design and methods. J. Neurotrauma 26, 2207-2216
37. Jennett, B., and Bond, M. (1975). Assessment of outcome after severe brain damage. Lancet 1, 480-484
38. Rappaport, M., Hall, K.M., Hopkins, K., Belleza, T., and Cope, D.N. (1982). Disability rating scale for severe head trauma: Coma to community. Arch. Phys. Med. Rehabil. 63, 118-123
39. Hamilton, B.B., Granger, C.V., Sherwin, F.S., Zielezny, M., and Tashman, J.S. (1987). A uniform national data system for medical rehabilitation, in: Rehabilitation Outcomes: Analysis and Measurement. M. Fuhrer (ed). Brookes: Baltimore, pps. 137-147
40. Brown, A.W., Malec, J.F., McClelland, R.L., Diehl, N.N., Englander, J., and Cifu, D.X. (2005). Clinical elements that predict outcome after traumatic brain injury: A prospective multicenter recursive partitioning (decision-Tree) analysis. J. Neurotrauma 22, 1040-1051
41. Andelic, N., Sigurdardottir, S., Schanke, A.K., Sandvik, L., Sveen, U., and Roe, C. (2010). Disability, physical health and mental health 1 year after traumatic brain injury. Disabil. Rehabil. 32, 1122-1131
42. Barnes, C., Conner, D., Legault, L., Reznickova, N., and Harrison- Felix, C. (2004). Rehabilitation outcomes in cognitively impaired patients admitted to skilled nursing facilities from the community. Arch. Phys. Med. Rehabil. 85, 1602-1607
43. Goyal, A., Failla, M.D., Niyonkuru, C., Amin, K., Fabio, A., Berger, R.P., and Wagner, A.K. (2013). S100b as a prognostic biomarker in outcome prediction for patients with severe traumatic brain injury. J. Neurotrauma 30, 946-957
44. Niyonkuru, C., Wagner, A.K., Ozawa, H., Amin, K., Goyal, A., and Fabio, A. (2013). Group-based trajectory analysis applications for prognostic biomarker model development in severe TBI: A practical example. J. Neurotrauma 30, 938-945
45. Nagin, D.S. (2005). Group-based Modeling of Development. Harvard University Press: Cambridge
46. Jones, B.L., Nagin, D., and Roeder, K. (2001). A SAS procedure based on mixture models for estimating developmental trajectories. Sociol. Meth. Res. 29, 374-393
47. Ho, J.T., Al-Musalhi, H., Chapman, M.J., Quach, T., Thomas, P.D., Bagley, C.J., Lewis, J.G., and Torpy, D.J. (2006). Septic shock and sepsis: A comparison of total and free plasma cortisol levels. J. Clin. Endocrinol. Metab. 91, 105-114
48. Holub, M., Beran, O., Dzupova, O., Hnykova, J., Lacinova, Z., Prihodova, J., Prochazka, B., and Helcl, M. (2007). Cortisol levels in cerebrospinal fluid correlate with severity and bacterial origin of meningitis. Crit. Care 11, R41
49. Baker, D.G., Ekhator, N.N., Kasckow, J.W., Dashevsky, B., Horn, P.S., Bednarik, L., and Geracioti, T.D. Jr. (2005). Higher levels of basal serial CSF cortisol in combat veterans with posttraumatic stress disorder. Am. J. Psychiatry 162, 992-994
50. Czech, C., Berndt, P., Busch, K., Schmitz, O., Wiemer, J., Most, V., Hampel, H., Kastler, J., and Senn, H. (2012). Metabolite profiling of Alzheimer's disease cerebrospinal fluid. PLoS One 7(2), e31501
51. Gerner, R.H., and Wilkins, J.N. (1983). CSF cortisol in patients with depression, mania, or anorexia nervosa and in normal subjects. Am. J. Psychiatry 140, 92-94
52. Erkut, Z.A., Endert, E., Huitinga, I., and Swaab, D.F. (2002). Cortisol is increased in postmortem cerebrospinal fluid of multiple sclerosis patients: Relationship with cytokines and sepsis. Mult. Scler. 8, 229-236
53. Boles, J.A., Goyal, A., and Wagner, A.K. (2013). Chronic inflammation after severe traumatic brain injury: Characterization and associations with outcome. J. Neurotrauma 30, A-1-A-183
54. Boles, J.A., Amin, K., Niyonkuru, C., Berger, R.P., Kochanek, P.M., Tisherman, S., and Wagner, A.K. (2012). The influence of isolated head injury status on inflammation cytokine levels post traumatic brain injury [abstract]. J. Neurotrauma 29, A35
55. Van Kalken, C.K., Broxterman, H.J., Pinedo, H.M., Feller, N., Dekker, H., Lankelma, J., and Giaccone, G. (1993). Cortisol is transported by the multidrug resistance gene product P-glycoprotein. Br. J. Cancer. 67, 284-289
56. Schinkel, A.H. (1999). P-Glycoprotein, a gatekeeper in the bloodbrain barrier. Adv. Drug Deliv. Rev. 36, 179-194
57. Loscher, W., and Potschka, H. (2005). Blood-brain barrier active efflux transporters: ATP-binding cassette gene family. NeuroRx. 2, 86-98
58. Karssen, A.M., Meijer, O.C., van der Sandt, I.C., Lucassen, P.J., de Lange, E.C., de Boer, A.G., and de Kloet, E.R. (2001). Multidrug resistance P-glycoprotein hampers the access of cortisol but not of corticosterone to mouse and human brain. Endocrinology 142, 2686-2694
59. Farrell, R.J., Menconi, M.J., Keates, A.C., and Kelly, C.P. (2002). PGlycoprotein-170 inhibition significantly reduces cortisol and ciclosporin efflux from human intestinal epithelial cells and T lymphocytes. Aliment. Pharmacol. Ther. 16, 1021-1031
60. Hartz, A.M., Bauer, B., Fricker, G., and Miller, D.S. (2006). Rapid modulation of P-glycoprotein-mediated transport at the blood-brain barrier by tumor necrosis factor-Alpha and lipopolysaccharide. Mol. Pharmacol. 69, 462-470
61. Roberts, D.J. and Goralski, K.B. (2008). A critical overview of the influence of inflammation and infection on P-glycoprotein expression and activity in the brain. Expert Opin. Drug Metab. Toxicol. 4, 1245-1264
62. Uhr, M., Holsboer, F., and Muller, M.B. (2002). Penetration of endogenous steroid hormones corticosterone, cortisol, aldosterone and progesterone into the brain is enhanced in mice deficient for both mdr1a and mdr1b P-glycoproteins. J. Neuroendocrinol. 14, 753-759
63. Pardridge, W.M., and Mietus, L.J. (1979). Transport of steroid hormones through the rat blood-brain barrier. Primary role of albuminbound hormone. J. Clin. Invest. 64, 145-154
64. Torpy, D.J., and Ho, J.T. (2007). Value of free cortisol measurement in systemic infection. Horm. Metab. Res. 39, 439-444
65. Strömstedt, M., and Waterman, M.R. (1995). Messenger RNAs encoding steroidogenic enzymes are expressed in rodent brain. Brain Res. Mol. Brain Res. 34, 75-88
66. Mellon, S.H., and Deschepper, C.F. (1993). Neurosteroid biosynthesis: Genes for adrenal steroidogenic enzymes are expressed in the brain. Brain Res. 629, 283-292
67. Chapman, K., Holmes, M. and Seckl, J. (2013). 11b-Hydroxysteroid dehydrogenases: Intracellular gate-keepers of tissue glucocorticoid action. Physiol. Rev. 93, 1139-1206
68. Wyrwoll, C.S., Holmes, M.C., and Seckl, J.R. (2011). 11b-Hydroxysteroid dehydrogenases and the brain: From zero to hero, a decade of progress. Front. Neuroendocrinol. 32, 265-286
69. MacKenzie, S.M., Clark, C.J., Fraser, R., Gomez-Sanchez, C.E., Connell, J.M., and Davies, E. (2000). Expression of 11b hydroxylase and aldosterone synthesis genes in the rat brain. J. Mol. Endocrinol. 24, 321-328
70. Frye, C.A. (2009). Neurosteroids' effects and mechanisms for social, cognitive, emotional, and physical functions. Psychoneuroendocrinology 34, Suppl 1, S143-S161
71. Stein, D.G. (2011). Progesterone in the treatment of acute traumatic brain injury: A clinical perspective and update. Neuroscience 191, 101-106
72. Meffre, D., Delespierre, B., Gouézou, M., Schumacher, M., Stein, D.G., and Guennoun, R. (2007). 3beta-Hydroxysteroid dehydrogenase/ 5-ene-4-ene isomerase mRNA expression in rat brain: Effect of pseudopregnancy and traumatic brain injury. J. Steroid Biochem. Mol. Biol. 104, 293-300
73. Patte-Mensah, C., Li, S., and Mensah-Nyagan, A.G. (2004). Impact of neuropathic pain on the gene expression and activity of cytochrome P450side-chain-cleavage in sensory neural networks. Cell Mol. Life Sci. 61, 2274-2284
74. Sorrells, S.F., Caso, J.R., Munhoz, C.D., and Sapolsky, R.M. (2009). The stressed CNS: When glucocorticoids aggravate inflammation. Neuron 64, 33-39
75. Caso, J.R., Moro, M.A., Lorenzo, P., Lizasoain, I., and Leza. J.C. (2007).Involvement of IL-1beta in acute stress-induced worsening of cerebral ischaemia in rats. Eur Neuropsychopharmacol. 17, 600-607
76. Sapolsky, R.M., and Pulsinelli, W.A. (1985). Glucocorticoids potentiate ischemic injury to neurons: Therapeutic implications. Science 229, 1397-1400
77. Barber, A.E., Coyle, S.M., Marano, M.A., Fischer, E., Calvano, S.E., Fong, Y., Moldawer, L.L., and Lowry, S.F. (1993). Glucocorticoid therapy alters hormonal and cytokine responses to endotoxin in man. J. Immunol. 150, 1999-2006
78. Johnson, J.D., O'Connor, K.A., Deak, T., Stark, M., Watkins, L.R., and Maier, S.F. (2002). Prior stressor exposure sensitizes LPS-induced cytokine production. Brain Behav. Immun.16, 461-476
79. Lupien, S.J., and McEwen, B.S. (1997). The acute effects of corticosteroids on cognition: Integration of animal and human model studies. Brain Res. Brain Res. Rev. 24, 1-27
80. McEwen, B.S., and Magarinos, A.M. (2001). Stress and hippocampal plasticity: Implications for the pathophysiology of affective disorders. Hum. Psychopharmacol. 16, S7-S19
81. Dinkel, K., MacPherson, A., and Sapolsky, R.M. (2003). Novel glucocorticoid effects on acute inflammation in the CNS. J. Neurochem. 84, 705-716
82. Sorrells, S.F., Caso, J.R., Munhoz, C.D., Hu, C.K., Tran, K.V., Miguel, Z.D., Chien, B.Y., and Sapolsky, R.M. (2013). Glucocorticoid signaling in myeloid cells worsens acute CNS injury and inflammation. J. Neurosci. 33, 7877-7889
83. Popoli, M., Yan, Z., McEwen, B.S., and Sanacora, G. (2011). The stressed synapse: The impact of stress and glucocorticoids on glutamate transmission. Nat. Rev. Neurosci. 13, 22-37
84. Bamberger, C.M., Schulte, H.M., and Chrousos, G.P. (1996). Molecular determinants of glucocorticoid receptor function and tissue sensitivity to glucocorticoids. Endocr. Rev. 17, 245-261
85. Guo, W.Z., Miao, Y.L., An, L.N., Wang, X.Y., Pan, N.L., Ma, Y.Q., Chen, H.X., Zhao, N., Zhang, H., Li, Y.F., and Mi, W.D. (2013). Midazolam provides cytoprotective effect during corticosterone-induced damages in rat astrocytes by stimulating steroidogenesis. Neurosci. Lett. 547, 53-58
86. Savaridas, T., Andrews, P.J., and Harris, B. (2004). Cortisol dynamics following acute severe brain injury. Intensive Care Med. 30, 1479-1483
87. Lin, J.H. (2008). CSF as a surrogate for assessing CNS exposure: An industrial perspective. Curr. Drug Metab. 9, 46-59
88. Liu, X., Smith, B.J., Chen, C., Callegari, E., Becker, S.L., Chen, X., Cianfrogna, J., Doran, A.C., Doran, S.D., Gibbs, J.P., Hosea, N., Liu, J., Nelson, F.R., Szewc, M.A., and Van Deusen, J. (2006) Evaluation of cerebrospinal fluid concentration and plasma free concentration as a surrogate measurement for brain free concentration. Drug Metab. Dispos. 34, 1443-1447
89. Liu, X., Van Natta, K., Yeo, H., Vilenski, O., Weller, P.E., Worboys, P.D., and Monshouwer, M. (2009). Unbound drug concentration in brain homogenate and cerebral spinal fluid at steady state as a surrogate for unbound concentration in brain interstitial fluid. Drug Metab. Dispos. 37, 787-793