Dynamics of CNS barriers: Evolution, differentiation, and modulation

Cellular and Molecular Neurobiology

Volumn 25, Issue 1, 2005, Pages 5-23

  Abbott, N Joan ^a  

^a KING'S COLLEGE LONDON   (United Kingdom)

Author keywords

Blood brain barrier; CNS; Evolution; Induction; Modulation

Indexed keywords

ASTROCYTE; BLOOD BRAIN BARRIER; BRAIN ARACHNOID; BRAIN BLOOD VESSEL; BRAIN CAPILLARY; CELL CULTURE; CELL DIFFERENTIATION; CELL ISOLATION; CENTRAL NERVOUS SYSTEM; CHOROID PLEXUS; ENDOTHELIUM; GENOMICS; GLIA CELL; HUMAN; IN VITRO STUDY; IN VIVO STUDY; MICROVASCULATURE; MOLECULAR DYNAMICS; MOLECULAR EVOLUTION; NERVE CELL DIFFERENTIATION; NEUROMODULATION; NONHUMAN; PRIORITY JOURNAL; PROTEOMICS; REVIEW; SIGNAL TRANSDUCTION; SYNAPSE;

ANIMALS; ASTROCYTES; BLOOD-BRAIN BARRIER; CELL DIFFERENTIATION; ENDOTHELIAL CELLS; EVOLUTION; HUMANS; SIGNAL TRANSDUCTION;

EID: 17644364388     PISSN: 02724340     EISSN: None     Source Type: Journal    
DOI: 10.1007/s10571-004-1374-y     Document Type: Review

References (105)

1. Abbott, N. J. (1992). Comparative physiology of the blood-brain barrier. In Bradbury, M. W. B. (ed.), Physiology and Pharmacology of the Blood-Brain Barrier, Springer-Verlag, Heidelberg, pp. 371-396.
2. Abbott, N. J. (1998). Role of intracellular calcium in regulation of brain endothelial permeability. In Pardridge W. M. (ed.) Introduction to the Blood-Brain Barrier: Methodology and Biology, Cambridge University Press, Cambridge, UK, pp. 345-353.
3. Abbott, N. J. (2000). Inflammatory mediators and modulation of blood-brain barrier permeability. Cell. Molec. Neurobiol. 20:31-147.
4. Abbott, N. J. (2002). Astrocyte-endothelial interactions and blood-brain barrier permeability. J. Anat. 200:629-638.
5. Abbott, N. J., and Revest, P. A. (1991). Control of brain endothelial permeability. Cerebrovasc. Brain Metab. Rev. 3:39-72.
6. Abbott, N. J., and Romero, I. A. (1996). Transporting therapeutics across the blood-brain barrier. Molec. Med. Today 2:106-113.
7. Abbott, N. J., and Romero, I. A. (1999). Patterns of toxic damage to brain endothelium in relation to cell metabolism. In Paulson, O., Moos Knudsen, G., and Moos, T. (eds.), Brain Barrier Systems, Alfred Benzon Symposium No 45, Munksgaard, Copenhagen, pp. 269-279.
8. Abbott, N. J., Bundgaard, M., and Cserr, H. F. (1986a). Comparative physiology of the blood-brain barrier. In Suckling, A. J., Rumsby, M. G., and Bradbury, M. W. (eds.) The Blood-Brain Barrier in Health and Disease, Ellis Horwood, Chichester, UK, pp. 52-72.
9. Abbott, N. J., Lane, N. J., and Bundgaard, M. (1986b). The blood-brain interface in invertebrates. Ann. NY Acad. Sci. 481:20-41.
10. Abbott, N. J., Mendonca, L. L. F., and Dolman, D. E. M. (2003). The blood-brain barrier in systemic lupus erythematosus. Lupus. 12:908-915.
11. Abbott, N. J., Revest, P. A., and Romero, I. A. (1992). Astrocyte-endothelial interaction: Physiology and pathology. Neuropath. Appl. Neurobiol. 18:424-433.
12. Abbott. N. J., Mitchell, G., Ward, K. J., Abdullah, F., and Smith, I. C. H. (1997). An electrophysiological method for measuring the potassium permeability of the nerve perineurium. Brain Res. 776:204-213.
13. Abbott, N. J., Zlokovic, B. V., Taylor, M., Hart, J., and Rogac, L. (1988). Amino acid transport by a glial blood-brain barrier: Studies in an elasmobranch fish. In Rakic, L., Begley, D. J., Davson, H., and Zlokovic B. V. (eds.), Peptide and Amino Acid Transport Mechanisms in the Central Nervous System, Macmillan Press and Serbian Academy of Sciences and Arts, London and Belgrade, pp. 241-244.
14. Ábrahám, C. S., Deli, M. A., Joó, F., Megyeri, P., and Torpier, G. (1996). Intracarotid tumour necrosis factor-α administration increases the blood-brain barrier permeability in the cerebral cortex of newborn pig: Quantitative aspects of double labelling studies and confocal laser scanning analysis. Neurosci. Lett. 208:85-88.
15. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., and Walter, P. (2002). Molecular Biology of the Cell, 4th edn., Garland Science, New York.
16. Allt, G., and Lawrenson, J. G. (1997). Is the pial microvessel a good model for blood-brain barrier studies? Brain Res. Rev. 24:67-76.
17. Allt, G., and Lawrenson, J. G. (2000). The blood-nerve barrier: Enzymes, transporters and receptors - a comparison with the blood-brain barrier. Brain Res. Bull. 52:1-12.
18. Allt, G., and Lawrenson, J. G. (2001). Pericytes: Cell biology and pathology. Cells Tissue Organs 169:1-11.
19. Amédée, T., Robert, A., and Coles, J. A. (1997). Potassium homeostasis and glial energy metabolism. Glia 21:46-55.
20. Arlotta, P., Magavi, S. S., and Macklis, J. D. (2003). Molecular manipulation of neural precursors in situ: Induction of adult cortical neurogenesis. Exp. Gerontol. 38:173-182.
21. Arsenijevic, D., Girardier, L., Seydoux, J., Pechere, J. C., Garcia, I., Lucas, R., Change, H. R., and Dulloo, A. G (1998). Metabolic-cytokine responses to a second immunological challenge with LPS in mice with T. gondii infection. Am. J. Physiol. 274: E439-E445.
22. Balda, M. S., Flores-Maldonado, C., Cereijido, M., and Matter, K. (2000). Multiple domains of occludin are involved in the regulation of paracellular permeability. J. Cell Biochem. 78:85-96.
23. Balda, M. S., Whitney, J. A., Flores, C., Gonzáles, S., Cereijido, M., and Matter, K. (1996). Functional dissociation of paracellular permeability and transepithelial resistance and disruption of the apical-basolateral intramembrane diffusion barrier by expression of a mutant tight junction membrane protein. J. Cell. Biol. 134:1031-1049.
24. Bauer, H. C., and Bauer, H. (2000). Neural induction of the blood-brain barrier: Still an enigma. Cell. Molec. Neurobiol. 20:13-28.
25. Bradbury, M. W. B. (1979). The Concept of a Blood-Brain Barrier, Wiley, Chichester, UK.
26. Brightman, M. W. (1992) Ultrastructure of brain endothelium. In Bradbury, M. W. B. (ed.), Physiology and Pharmacology of the Blood-Brain Barrier, Springer-Verlag, Heidelberg, pp. 1-22.
27. Brightman, M. W., and Reese, T. S. (1969). Junctions between intimately apposed cell membranes in the vertebrate brain. J. Cell Biol. 40:648-677.
28. Butt, A. M. (1995). Effect of inflammatory agents on electrical resistance across the blood-brain barrier in pial microvessels of anaesthetized rats. Brain Res. 696:145-50.
29. Butt, A. M., Jones, H. C., and Abbott, N. J. (1990). Electrical resistance across the blood-brain barrier in anaesthetized rats: A developmental study. J. Physiol. 429:47-62.
30. Chen, K. C., and Nicholson, C. (2000). Spatial buffering of potassium ions in brain extracellular space. Biophys. J. 78:2776-2797.
31. Conti, L., Cataudella, T., and Cattaneo, E. (2003). Neural stem cells: A pharmacological tool for brain diseases? Pharmacol. Res. 47:289-297.
32. Cserr, H. F., and Bundgaard, M. (1984). Blood-brain interface in vertebrates: A comparative approach. Am. J. Physiol. R246:277-288.
33. Cserr, H. F., and Patlak, C. S. (1992) Secretion and bulk flow of interstitial fluid. In Bradbury, M. W. B. (ed.), Physiology and Pharmacology of the Blood-Brain Barrier, Springer Verlag, Berlin, pp. 245-261.
34. Davson, H., and Segal, M. B. (1995). Physiology of the CSF and the Blood-Brain Barrier, CRC Press, New York.
35. De Vries, H. E., Kuiper, J., de Boer, A. G., Van Berkel, T. J. C., and Breimer, D. D. (1997). The blood-brain barrier in neuroinflammatory diseases. Pharmacol. Rev. 49:143-155.
36. Dehouck, M.-P., Meresse, S., Delorme, P., Fruchart, J.-C., and Cecchelli, R. (1990). An easier, reproducible, and mass-production method to study the blood-brain barrier in vitro. J. Neurochem. 54:1798-1801.
37. Deli, M. A., Ábrahám, C. S., Kataoka, Y., and Niwa, M. (2005). Permeability studies on in vitro BBB models: Physiology, pathology, pharmacology. Cell. Molec. Neurobiol. 25:59-127.
38. Demeule, M., Regina, A., Jodoin, J., Laplante, A., Dagenais, C., Berthelet, F., Moghrabi, A., and Beliveau, R. (2002). Drug transport to the brain: Key roles for the efflux pump P-glycoprotein in the blood-brain barrier. Vasc. Pharmacol. 38:339-348.
39. Desai, S., Marroni, M., Cucullo, L., Bengez, L., Mayberg, M., Hosssain, M., Grant, G., and Janigro, D. (2002). Mechanisms of endothelial survival under shear stress. Endothelium 9:89-102.
40. Doolittle, N. D., Miner, M. E., Hall, W. A., Siegal, T., Jerome, E., Osztie, E., McAllister, L. D., Bubalo, J. S., Kraemer, D. F., Fortin, D., Nixon, R., Muldoon, L. L., and Neuwelt, E. A. (2000). Safety and efficacy of a multicenter study using intraarterial chemotherapy in conjunction with osmotic opening of the blood-brain barrier for the treatment of patients with malignant brain tumours. Cancer 88:637-647.
41. Duport, S., Robert, F., Muller, D., Grau, G., Parisi, L., and Stoppini, L. (1998). An in vitro blood-brain barrier model: Cocultures between endothelial cells and organotypic brain slice cultures. Proc. Natl. Acad. Sci. USA 95:1840-1845.
42. Easton, A. S., and Abbott, N. J. (2002). Bradykinin increases permeability by calcium and 5-lipoxygenase in the ECV304/C6 cell culture model of the blood-brain barrier. Brain Res. 953:157-169.
43. Easton, A. S., Sarker, M. H., and Eraser, P. A. (1997). Two components of blood-brain barrier disruption in the rat. J. Physiol. 503:613-623.
44. El Hafny, B., Bourre, J.-M., and Roux, F. (1996). Synergistic stimulation of gamma-glutamyl transpeptidase and alkaline phosphatase activities by retinoic acid and astroglial factors in immortalized rat brain microvessel endothelial cells. J. Cell. Physiol. 167:451-460.
45. El Hafny, B., Chappey, O., Piciotti, M., Debray, M., Boval, B., and Roux, F. (1997). Modulation of P-glycoprotein activity by glial factors and retinoic acid in an immortalized rat brain microvessel endothelial cell line. Neurosci. Lett. 236:107-111.
46. Engelhardt, B., and Risau, W. (1995). Development of the blood-brain barrier. In Greenwood, J., Begley, D. J., and Segal, M. B. (eds), New Concepts of the Blood-Brain Barrier, Plenum Press, New York and London, pp. 11-33.
47. Fenstermacher, J., Nakata, H., Tajima, A., Yen, M.-H., Acuff, V., and Gruber, K. (1992). Structural, ultrastructural and functional correlations among local capillary systems within the brain. In: Segal, M. B. (ed.), Barriers and Fluids of the Eye and Brain, Macmillan Press, London, pp. 59-71.
48. Gaillard, P. J., and de Boer, A. G. (2000). Relationship between permeability status of the blood-brain barrier and in vitro permeability coefficient of a drug. Eur. J. Pharm. Sci. 12:95-102.
49. Ghersi-Egea, J. F., Finnegan, W., Chen, J. L., and Fenstermacher, J. D. (1996). Rapid distribution of intraventricularly administered sucrose into cerebrospinal fluid cisterns via subarachnoid velae in rat. Neuroscience 75:1271-1288.
50. Haseloff, R. F., Blasig I. E., Bauer, H.-C., and Bauer, H. (2005). In search of the astrocytic factor(s) modulating blood-brain barrier functions in brain capillary endothelial cells in vitro. Cell. Molec. Neurobiol. 25:25-39.
51. Hickey, W. F. (2001). Basic principles of immunological surveillance of the normal central nervous system. Glia 36:118-124.
52. Hoheisel, D., Nitz, T., Franke, H., Wagner, J., Hakvoort, A., Tilling, T., and Galla, H. J. (1998). Hydrocortisone reinforces the blood-brain barrier properties in a serum free cell culture system. Biochem. Biophys. Res. Comm. 247:312-315.
53. Hosoya, K., Ohtsuki, S., and Terasaki, T. (2002). Recent advances in the brain-to-blood efflux transport across the blood-brain barrier. Int. J. Pharm. 248:15-29.
54. Huber, J. D., Egleton, R. D., and Davis, T. P. (2001). Molecular physiology and pathophysiology of tight junctions in the blood-brain barrier. Trends Neurosci. 24:719-725.
55. Hurst, R. D., and Fritz, I. B. (1996a). Properties of an immortalised vascular endothelial/glioma cell co-culture model of the blood-brain barrier. J. Cell. Physiol. 167:81-88.
56. Hurst, R. D., and Fritz, I. B. (1996b) Nitric oxide-induced perturbations in a cell culture model of the blood-brain barrier. J. Cell. Physiol. 167:89-94.
57. Igarashi, Y., Utsumi, H., Chiba, H., Yamada-Sasamori, Y., Tobioka, H., Kamimura, Y., Furuuchi, K., Kokai, Y., Nakagawa, T., Mori, M., and Sawada N. (1999). Glial cell line-derived neurotrophic factor induces barrier function of endothelial cells forming the blood-brain barrier. Biochem. Biophys. Res. Commun. 261:108-112.
58. Joó, F., and Karnushina, I. (1973). A procedure for the isolation of capillaries from rat brain. Cytobios 8:41-48.
59. Kacem, K., Lacombe, P., Seylaz, J., and Bonvento, G. (1998). Structural organization of the perivascular astrocyte endfeet and their relationship with the endothelial glucose transporter: A confocal microscopy study. Glia 23:1-10.
60. Konsman, J. P., Tridon, V., and Dantzer, R. (2000). Diffusion and action of intracerebroventricularly injected interleukin-1 in the CNS. Neuroscience 101:957-967.
61. Kraemer, D. F., Fortin, D., and Neuwelt, E. A. (2002). Chemotherapeutic dose intensification for treatment of malignant brain tumors: Recent developments and future directions. Curr. Neurol. Neurosci. Rep. 2:216-224.
62. Krämer, S. D., Abbott, N. J., and Begley, D. J. (2001). Biological models to study blood-brain barrier permeation. In Testa, B., van de Waterbeemd, H., Folkers, G., and Guy, R. (eds.), Pharmacokinetic Optimization in Drug Research: Biological, Physicochemical and Computational Strategies, Weinheim, Wiley-VCH, pp. 127-153.
63. Krum, J. M., Kenyon, K. L., and Rosenstein, J. M. (1997). Expression of blood-brain barrier characteristics following neuronal loss and astroglial damage after administration of anti-Thy-1 immunotoxin. Exp. Neurol. 146:33-45.
64. Li, J. Y., Boado, R. J., and Pardridge, W. M. (2001). Blood-brain barrier genomics. J. Cereb. Blood Flow Metab. 21:61-68.
65. Mandel, L. J., Bacallao, R., and Zampighi, G. (1993). Uncoupling of the molecular "fence" and paracellular "gate" functions of epithelial tight junctions. Nature 361:552-555.
66. Male, D. K. (1992). Immunology of brain endothelium and the blood-brain barrier. In Bradbury, M. W. B. (ed.), Physiology and Pharmacology of the Blood-Brain Barrier, Springer Verlag, Berlin, pp. 397-415.
67. Marroni, M., Marchi N., Cucullo, L., Abbott, N. J., Signorelli, K., and Janigro, D. (2003). Vascular and parenchymal mechanisms in multiple drug resistance: A lesson from human epilepsy. Curr. Drug Targets 4:279-304.
68. Mayhan, W. G. (2001). Regulation of blood-brain barrier permeability. Microcirculation 8:89-104.
69. Mizuguchi, H., Utoguchi, N., and Mayumi, T. (1997). Preparation of glial extracellular matrix: A novel method to analyze glial-endothelial interaction. Brain Res. Protoc. 1:339-343.
70. Moos, T. (2002). Brain iron homeostasis. Danish Med. Bull. 49:279-301.
71. Nagy, Z., Peters, H., and Hüttner, I. (1984). Fracture faces of cell junctions in cerebral endothelium during normal and hyperosmotic conditions. Lab. Invest. 50:313-322.
72. Nobles, M., Revest, P. A., Couraud, P.-O., and Abbott, N. J. (1995). Characteristics of nucleotide receptors that cause elevation of cytoplasmic calcium in immortalized rat brain endothelial cells (RBE4) and in primary cultures. Br. J. Pharmacol. 115:1245-1252.
73. Nobles, M., and Abbott, N. J. (1996). Adhesion and growth of brain microvascular endothelial cells on treated glass. Endothelium 4:297-307.
74. i in rat brain microvascular endothelial cells. Eur. J. Pharmacol. 361:19-127.
75. Olesen, S.-P. (1989). An electrophysiological study of microvascular permeability and its modulation by chemical mediators. Acta Physiol. Scand. 136(Suppl. 579):1-28.
76. Papadopoulos, M. C., Saadoun, S., Woodrow, C. J., Davis, D. C., Costa-Martins, P., Moss, R. F., Krishna, S., and Bell, B. A. (2001). Occludin expression in microvessels of neoplastic and non-neoplastic human brain. Neuropath. Appl. Neurobiol. 27:384-395.
77. Pasqualini, R., Arap, W., and McDonald, D. M. (2002). Probing the structural and molecular diversity of tumor vasculature. Trends Molec. Med. 8:563-571.
78. Perry, V. H., Anthony, D. C., Bolton, S. J., and Brown H. C. (1997). The blood-brain barrier and the inflammatory response. Mol. Med. Today 3:225-341.
79. Plumb, J., McQuaid. S., Mirakur, M., and Kirk, J. (2002). Abnormal endothelial tight junctions in active lesions and normal-appearing white matter in multiple sclerosis. Brain Path. 12:154-169.
80. 14C]inulin in rat. Neuroscience 2:577-592.
81. Ramsauer, M., Krause, D., and Dermietzel, R. (2002). Angiogenesis of the blood-brain barrier in vitro and the function of cerebral pericytes. FASEB J. 16:1274-1276.
82. Rapoport, S. I. (2001). Advances in osmotic opening of the blood-brain barrier to enhance CNS chemotherapy. Expert Opin. Investig. Drugs 10:1809-1818.
83. Regina, A., Koman, A., Piciotti, M., El Hafny, B., Center, M. S., Bergmann, R., Couraud, P. O., and Roux, F. (1998). Mrp1 multidrug resistance-associated protein and P-glycoprotein expression in rat brain microvessel endothelial cells. J. Neurochem. 71:705-715.
84. Reichel, A., Begley, D. J., and Abbott, N. J. (2003). An overview of in vitro techniques for blood-brain barrier studies. In Nag, S. (ed.), The Blood-Brain Barrier, Biology and Research Protocols, Humana Press, Totowa, New Jersey, pp. 307-324.
85. Reinhart, C. A., and Gloor, S. M. (1997). Co-culture blood-brain barrier models and their use for pharmatoxicological screening. Toxicol. in Vitro 11:513-518.
86. Rennels, M. L., Gregory, T. F., Blaumanis, O. R., Fujimoto, K., and Grady, P. A. (1985). Evidence for a 'paravascular' fluid circulation in the mammalian central nervous system, provided by the rapid distribution of tracer protein throughout the brain from the subarachnoid space. Brain Res. 326:47-63.
87. 2+] in cultured rat brain capillary endothelial cells. Brain Res. 549:159-161.
88. Risau, W., and Wolburg, H. (1990). Development of the blood-brain barrier. Trends. Neurosci. 13:174-178.
89. Rubin, L. L., Hall, D. E., Porter, S., Barbu, K., Cannon, C., Horner, H. C., Janatpour, M., Liaw, C. W., Manning, K., Morales, J., Tanner, L. I., Tomaselli, K. J., and Bard, F. (1991). A cell culture model of the blood-brain barrier. J. Cell Biol. 115:1725-1735.
90. Saunders, N. R. (1992). Ontogenetic development of brain barrier mechanisms. In Bradbury, M. W. B. (ed.), Physiology and Pharmacology of the Blood-Brain Barrier, Springer Verlag, Berlin, pp. 327-369.
91. Schroeter, M. L., Mertsch, K., Giese, H., Muller, S., Sporbert, A., Hickel, B., and Blasig, I. E. (1999). Astrocytes enhance radical defence in capillary endothelial cells constituting the blood-brain barrier. FEBS Lett. 449:241-244.
92. Schulze, C., and Firth, J. A. (1993). Immunohistochemical localization of adherens junction components in blood-brain barrier microvessels of the rat. J. Cell Sci. 104:773-782.
93. Segal, M. B., and Zlokovic, B. V. (1990). The Blood-Brain Barrier, Amino Acids and Peptides, Kluwer, Dordrecht, Boston, London.
94. Sipos, I., Dömötör, E., Abbott, N. J., and Adam-Vizi, V. (2000). The pharmacology of nucleotide receptors on primary rat brain endothelial cells grown on a biological extracellular matrix: Effects on intracellular calcium concentration. Br. J. Pharmacol. 131:1195-1203.
95. Stanness, K. A., Westrum, L. E., Mascagni, P., Fornaciari, E., Nelson, J. A., Stenglein, S. G., and Janigro, D. (1997). Morphological and functional characterization of an in vitro blood-brain barrier model. Brain Res. 771:329-342.
96. Syková, E., Hansson, E., Rönnbäck, L., and Nicholson, C. (1998). Glial regulation of the neuronal microenvironment. In Laming, P. R., Syková, E., Reichenbach, A., Hatton, G. I., and Bauer, H. (eds.), Glial Cells: Their Role in Behaviour, Cambridge University Press, Cambridge, pp. 130-163.
97. Tontsch, U., and Bauer H.-C. (1991). Glial cells and neurons induce blood-brain barrier related enzymes in cultured cerebral endothelial cells. Brain Res. 539:247-253.
98. Trepel, M., Arap, W., and Pasqualini, R. (2002). In vivo phage display and vascular heterogeneity: Implications for targeted medicine. Curr. Opin. Chem. Biol. 6:399-404.
99. Utsumi, H., Chiba, H., Kamimura, Y., Osanai, M., Igarashi, Y., Tobioka, H., Mori, M., and Sawada, N. (2000). Expression of GFRa-1, receptor for GDNF, in rat brain capillary during postnatal development of the BBB. Am. J. Physiol., Cell Physiol. 279:C361-C368.
100. Weller, R. O., Kida, S., and Zhang, E.-T. (1992). Pathways of fluid drainage form the brain - morphological aspects and immunological significance in rat and man. Brain Path. 2:277-284.
101. Westergaard, E., and Brightman, M. W. (1973). Transport of proteins across segments of cerebral arterioles under normal conditions. J. Comp. Neurol. 152:17-44.
102. Wolburg, H., and Lippoldt, A. (2002). Tight junctions of the blood-brain barrier: Development, composition and regulation. Vasc. Pharmacol. 38:332-337.
103. Yamagata, K., Tagami, M., Takenaga, F., Yamori, Y., Nara, Y., and Itoh, S. (2003). Polyunsaturated fatty acids induce tight junctions to form in brain capillary endothelial cells. Neuroscience 116:649-656.
104. Xaio, H., Banks, W. A., Niehoff, M. L., and Morley, J. E. (2001). Effect of LPS on the permeability of the blood-brain barrier to insulin. Brain Res. 896:36-42.
105. Zenker, D., Begley, D., Rübsamen-Waigmann, H., and von Briesen, H. (2001). Effects of macrophages on the blood-brain barrier properties of cultured brain capillary endothelial cells. J. Physiol. 531P:209P.