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How can I study brain penetration of an drug using invivo animal model?
Vishal Pendharkar
Research Assistant,
Suven Pharmaceuticals,
R & D centre, Plot no. 18B,
Phase III,IDA,Jeedimetla,
Hyderabad 500055.
Cell Phone no. +919849485651
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The following message was posted to: PharmPK
Microdialysis sampling can be used to look at the drug distribution in
brain. Microdialysis involves implanting a dialysis probe in the brain
and frequent sampling while perfusing the probe with artificial CSF or
Ringers solution. The samples are protein-free so you can directly
inject to the analytical system for drug assay. The animal is awake and
freely-moving through the sampling. I am happy to provide more details
if you are interested.
Chandrani Gunaratna
Chandrani Gunaratna, Ph.D.
Senior Research Scientist
Bioanalytical Systems
2701 Kent Avenue
West Lafayette, IN 47906
(765)463-4527
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Vishal,
There are various ways you could do invivo brain pemeability studies.
The most commonly used techniques arebrain uptake index (BUI), brain
perfusion and microdialysis. Willam pardridge has done lot of work in
this area and you could refer to some of his review papers, which
discusses about pros and cons of these techniques. You may also want to
look into papers published by Ron Swachuk for microdialysis studies and
brain perfusion by Quentin Smith.
Azher Hussain, Ph.D
Research Scientist III
Drug Metabolism
Wyeth Research
hussaiA1.at.wyeth.com
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Hello Vishal:
There are many ways to study the ability of a drug to cross Blood Brain
Barrier (BBB), and distributionin brain:
A conventional approach is tosacrifice animals at different time
points post dosing and surgically remove the brain, its quite easy in
mice, care should be taken not to contaminate brain with blood
whileremoval. The collected brain samples can be homogenized with
appropriate dilution with buffer and extracted and analyzed, to
generate a drug brain profile. Its advisable to collect blood samples
at the corresponding brain sampling points for determining
tissue:plasma ratio.
Another widely used technique for measuring drug brain levels in freely
moving animals is Microdialysis, where a probe is surgically implanted
in the brain, the method requires calibration of the probe and numerous
literature reportsare available, you may like to refer some of the
recent work in this area :
Tsai TH, Chen YF. Pharmacokinetics of metronidazole in rat blood, brain
and bile studied by microdialysis coupled to microbore liquid
chromatography.J Chromatogr A. 2003 Feb 14;987(1-2):277-82.
A sensitive new method to study cerebrovascular transfer in the rat is
in situ rat brain perfusion, some of the recent work
Lockman PR, Mumper RJ, Allen DD. Evaluation of blood-brain barrier
thiamine efflux using the in situ rat brain perfusion method J
Neurochem. 2003 Aug;86(3):627-34.
A reliablein vitro model for BBB studies is transport studies across
Bovine Brain Microvessel Endothelial Cells. A good approach to
understand thebehaviorof a compound at BBB would be to evaluate it
onboth in vitro and in vivo models. A recent study using both of this
approach is:
Raje S, Cao J, Newman AH, Gao H, Eddington ND. Evaluation of the Blood
Brain Barrier Transport, Population Pharmacokinetics and Brain
Distribution of Benztropine Analogs and Cocaine Using In Vitro and In
Vivo Techniques. J Pharmacol Exp Ther. 2003 Sep 9 [Epub ahead of print].
Hope this will help you in planning your study,good luck
Vijay V. Upreti.
Department of Pharmaceutical Sciences. School of Pharmacy, University
of Maryland. Baltimore. MD 21201. USA
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It has been stated:
“There are many ways to study the ability of a drug to cross Blood
Brain Barrier and distribution in the brain”, such as “brain samples
can be homogenized…”, also microdialysis may be performed. Such was a
response to a recent inquiry.
Yes, there are many methods recommended and frequently used. How useful
are these expedient methods? Can they answer the question about
crossing of BBB and distribution?
There is a long history about attempts to localize in vivo sites of
drugs in the brain. Roth, forty years ago a professor at the Department
of pharmacology of the University of Chicago, used to walk up to
speakers at pharmacology meetings, handing out his name card that
stated on its back: “Don’t homogenize the brain, the brain you are
homogenizing may be your own”.
Here is an example [not attached - db]: radioassays of brain samples
and whole body
autoradiography have failed to find and localize vitamin D in the brain
and spinal cord. But with receptor micro autoradiography we have
published maps of specific binding sites in many regions of the brain
and spinal cord in rats, mice, hamster, birds, reptiles and fish. Below
are autoradiograms of brain amygdala and in spinal cord anterior horn.
The subject matter is discussed in detail in Stumpf WE: Drug
Localization in Tissues and Cells. IDDC-Press, Chapel Hill, NC. 2003 –
obtainable through UNC Student Stores: Erica Eisdorfer: Phone: (919)
962-2420. E-mail: eisdorfer.-at-.unc.edu
With best regards, Walter E. Stumpf
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