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The following message was posted to: PharmPK
How can I study brain penetration of an drug using invivo animal model?
What will the type for brain peneration index?
With regards
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The following message was posted to: PharmPK
Hello,
I suggest that a quick Medline etc search would have answered your
question pretty easily.
However, at the risk of pushing my and my collegues own wagon here are a
few references where we use a chronically instrumented sheep that I
found in about 30 seconds on PubMed:
1: Villesen HH, Foster DJ, Upton RN, Somogyi AA, Martinez A, Grant C.
Cerebral kinetics of oxycodone in conscious sheep.
J Pharm Sci. 2006 May 25; [Epub ahead of print]
PMID: 16729270 [PubMed - as supplied by publisher]
2: Foster DJ, Jensen ML, Upton RN, Somogyi AA, Grant C, Martinez A.
Blood-brain equilibration kinetics of levo-alpha-acetyl-methadol using
a
chronically instrumented sheep preparation.
Br J Pharmacol. 2006 Jan;147(2):209-17.
PMID: 16299549 [PubMed - in process]
3: Foster DJ, Upton RN, Somogyi AA, Grant C, Martinez A.
The acute disposition of (R)- and (s)-methadone in brain and lung of
sheep.
J Pharmacokinet Pharmacodyn. 2005 Aug;32(3-4):547-70.
PMID: 16284915 [PubMed - in process]
4: Rasmussen M, Upton RN, Grant C, Martinez AM, Cold GE, Ludbrook G.
The effects of indomethacin on intracranial pressure and cerebral
hemodynamics
during isoflurane or propofol anesthesia in sheep with intracranial
hypertension.
Anesth Analg. 2006 Jun;102(6):1823-9.
PMID: 16717332 [PubMed - in process]
5: Doolette DJ, Upton RN, Martinez AM.
Brain pharmacokinetics of lignocaine before and following intravenous
perfluorocarbon emulsion infusion in sheep.
Clin Exp Pharmacol Physiol. 2005 May-Jun;32(5-6):367-71.
PMID: 15854143 [PubMed - indexed for MEDLINE]
6: Upton RN, Grant C, Martinez AM, Ludbrook GL.
Recirculatory model of fentanyl disposition with the brain as the
target organ.
Br J Anaesth. 2004 Nov;93(5):687-97. Epub 2004 Sep 17.
PMID: 15377588 [PubMed - indexed for MEDLINE]
7: Upton RN, Ludbrook GL, Martinez AM, Grant C, Milne RW.
Cerebral and lung kinetics of morphine in conscious sheep after short
intravenous infusions.
Br J Anaesth. 2003 Jun;90(6):750-8.
PMID: 12765891 [PubMed - indexed for MEDLINE]
8: Myburgh JA, Upton RN, Grant C, Martinez A.
The effect of infusions of adrenaline, noradrenaline and dopamine on
cerebral
autoregulation under propofol anaesthesia in an ovine model.
Intensive Care Med. 2003 May;29(5):817-24. Epub 2003 Feb 21.
PMID: 12595982 [PubMed - indexed for MEDLINE]
9: Myburgh JA, Upton RN, Grant C, Martinez A.
The cerebrovascular effects of adrenaline, noradrenaline and dopamine
infusions
under propofol and isoflurane anaesthesia in sheep.
Anaesth Intensive Care. 2002 Dec;30(6):725-33.
PMID: 12500509 [PubMed - indexed for MEDLINE]
10: Myburgh JA, Upton RN, Ludbrook GL, Martinez A, Grant C.
Cerebrovascular carbon dioxide reactivity in sheep: effect of propofol
or
isoflurane anaesthesia.
Anaesth Intensive Care. 2002 Aug;30(4):413-21.
PMID: 12180577 [PubMed - indexed for MEDLINE]
Regards,
David
David Foster, PhD
Lecturer
School of Pharmacy and Medical Sciences
Room P4-08
City East Campus
University of South Australia
Adelaide SA 5000
CRICOS Provider Number: 00121B
Phone: 61 8 8302 2055
Fax: 61 8 8302 2389
Email: david.foster.aaa.unisa.edu.au
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Hi.
I did a honours project some time ago on brain perfusion in the rat.
I used a technique which basically involved the bilateral cannulation
of the carotid arteries; the actual surgery involved tying off the
external carotid arteries to restrict circulation to the brain and
not the extracerebral structures, i.e., ears, eyes. Following the
cannulation, I pumped in aq. buffer of physiological pH and glucose
concentrations for about an hour to achieve equilibration. Then I
started to pump in my test compound. Out-perfusate was venous and
dripped out of the head which I had dissected away from the body and
held in position over a filter funnel. Though the setup was crude, it
served its purpose. If you'd like more references to this method, I'd
suggest you look up the Japanese author, Takasato et al.. He and his
team pioneered work in this area.
You might also want to try more novel methods include PET scanning if
you have the facilities.
Anand
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Hi Gopi Raj, there are couple of approaches that could be used to
study brain penetration. It depends upon how much detailed
information you need. If you just need brain to plasma or brain to
blood ratio and there is some pharmacokinetic information about your
drug, then you can bring the animal to steady state using infusion
and then take brain and blood samples. If you need kinetics of brain
penetration or if you need to determine the mechanism of brain
penetration then you might want to look at insitu technique. Brain
penetration index is provided by the technique known as brain uptake
index. There are certain drawbacks with this method and the in situ
technique would be more preferable. Hope this helps.
Indranil Bhattacharya
DMPK
GlaxoSmithKline
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The following message was posted to: PharmPK
How to study BRAIN PENETRATION ?
(response to Gopi Raj and Indranil Bhattacharya)
Please consider these explorations of brain:
ESTRADIOL was at first not found in brain, only when hypothalamus was
excised and radio-assayed separately was receptor binding observed
(Eisenfeld).
CORTISOL was discovered in brain, when hippocampus was excised and
assayed separately (McEwen).
PROGESTERONE uptake was published as not present in brain. Only four
years after the demonstration of selective binding with Receptor
Microscopic Autoradiography, brain uptake was confirmed with
topographical biochemistry.
VITAMIN D was reported as negative in brain with radioassay and also
with whole body autoradiography; a blood brain barrier was postulated.
Using our microscopic approach, we published maps of neuron target
circuits in brain and spinal cord for estrogen, gluco-corticoid, and
vitamin D, contrasting with and extending radioassay data. These are
samples of a larger list in the literature.
There is no blood brain barrier for circumventricular organs, and
compounds may easily enter these important brain structures. Certain
compounds penetrate slowly through ventricular ependyma ? like
dexamethasone.
Topograpjical biochemistry and high resolution autoradiography
approaches may need to be considered case by case. ? The
considerations given to brain here, similarly apply to other organs
as well!
As Lloyd Roth once remarked:?Don?t homogenize the brain, the brain
you are homogenizing may be your own?. ? I discussed this topic
repeatedly and extensively, e.g., in the book: Drug Localization in
Tissues and Cells; and in recent articles published in: J Pharmacol
Toxicol Methods 51(2005):25-40 and in: Drug Discovery Today 11(2006):
550-555.
Walter E. Stumpf
(www.walterstumpf.com)
--
Walter E Stumpf
2612 Damascus Church Rd
Chapel Hill, NC 27516
Tel/Fax: 919 942 8646
www.walterstumpf.com
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Dr. Stumpf has pointed out a very important aspect of all PK studies
i.e. analytical sensitivity. This has to be considered before
performing any experiment. With in situ brain perfusion one can
determine regional distribution (preferably with C14 labeled, than
H3) but due to small amount of tissue obtained in studying regional
distribution one might not detect brain penetration. This warrants
the use of more sensitive methods as he mentioned.
Another question to be thought about is what is the CNS activity of
the compound. An observed concentration in the brain however might
not necessarily translate into significant CNS activity if the free
concentration is minute compared to the Kd of receptor binding and
that should be considered separately. Also nonspecific binding occurs
and that warrants separate attention.
It all depends upon the reason(s) one wants to investigate something
and the associated implications rather than just the findings
(positive or negative).
Indranil Bhattacharya
DMPK
GlaxoSmithKline
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The following message was posted to: PharmPK
Dear Indranil,
Accelerator Mass Spectrometry could be the answer to problems associated
with sensitivity for these studies. Especially if ou are using 14C
labeled compounds.
We have some analytical capabilities you may be interested in.
Best regards,
Michael
Michael Chansler
Vice President Business Development and Sales
Accium BioSciences
550 17th Avenue, Suite 550
Seattle, WA 98122
Tel: (206) 281-3915
Fax: (206) 281-5916
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The following message was posted to: PharmPK
Dear Idranil,
To evaluate the penetration of a drug into the brain , we use,
routinely, a human in vitro model developped by Dr Mabondzo, CEA.
This model allows both kinetic and mechanistic studies.
You can read the following issues:
1- I. Megard, A. Garrigues, S. Orlowski, S. Jorajuria, P. Clayette,
E. Ezan, & A. Mabondzo. A coculture-based model of human blood-brain
barrier: application to active transport of indinavir and in vivo-in
vitro correlation.
Brain research 927 (2002) 153-167.
2- Josserand V, Pelerin H, de Bruin B, Jego B, Kuhnast B, Hinnen F,
Duconge F, Boisgard R, Beuvon F, Chassoux F, Daumas-Duport C, Ezan E,
Dolle F, Mabondzo A, Tavitian B. Evaluation of drug penetration into
the brain: a double study by in vivo imaging with positron emission
tomography and using an in vitro model of the human blood-brain barrier.
J Pharmacol Exp Ther. 2006 Jan;316(1):79-86.
Regards,
Laurent BAUDUIN
SPIBIO
CEA Saclay
Batiment 136
DSV/DRM/SPI
91191 GIF SUR YVETTE - FRANCE
tel : 33-1-69-08-97-09
fax : 33-1-69-08-59-07
email: laurent.bauduin.aaa.cea.fr
website: www.spibio.com
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I find these comments interesting and thought-provoking. From my med
chem experience with small-molecues, most of the drug in the brain is
non-specifically bound to tissue and a small part of the total amount
in brain is actually bound to the target (at least at therapeutic
doses). Receptor densities are in the order of femtomol/g specific
brain tissue.
For the examples listed in your message, I would expect lipophilic
steroids like estradiol, cortisol and progesterone to show
significant non-specific tissue binding. What kind of affinity
parameters and receptor densities are required for such compounds to
bind to a target receptor at very low concentrations that are not
significantly detected in the rest of the brain tissue?
Thanks,
Dario
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The following message was posted to: PharmPK
How can I study brain penetration of an drug using in-vivo animal model?
What will the type for brain penetration index?
With regards
Gopiraj
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The following message was posted to: PharmPK
Gopiraj:
There are basically two types of methods that can be used to study
what you call the Brain penetration index (BPI), which represents the
relative concentration of radioactivity in brain to that in the liver
(mean +/- SEM).
The first is the classical cut-and-count. You inject the drug,
euthanize the animal at time t, measure activity in the brain and in
the liver. The advantage is that such a technique can be done
anywhere, the limitation is that you get only a single time point per
animal.
The second is using noninvasive imaging, nuclear (usually PET),
magnetic resonance spectroscopy or optical imaging. These techniques
are much more sophisticated - and much more expensive, but give you
much more detailed information and can be used to study the effect of
various conditions and agents on the biodistribution of your drug.
What you have to determine is what is the information you really
need, and what are the resources you have available.
Professor Walter Wolf, Ph.D.
Distinguished Professor of Pharmaceutical Sciences
Director, Pharmacokinetic Imaging Program
Department of Pharmaceutical Sciences, School of Pharmacy
Chair, Biomedical Imaging Science Initiative
University of Southern California
1985 Zonal Ave., Los Angeles, 90089-9121
Tel: 323-442-1405
Fax: 323-442-9804
E-mail: wwolfw.at.usc.edu
http://www.usc.edu/research/initiatives/biomedical_imaging/index.html
http://www.usc.edu/schools/pharmacy/faculty_directory/detail.php?id=59
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The following message was posted to: PharmPK
Could you explain better the relationship between liver and brain
regarding the ability of a drug to pass the BBB?
I know that generally a tissue to blood ratio is used
Thank you
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DEAR
brain is a highly thick membrane . so only limited drugs can cross
BBB.but liver maximum drugs are metabolised by the liver . So drug
distribution more in liver .
A.karthik
DMPK LAB,DISCOVERY RESEARCH
DR REDDYS LABORATORIES LTD
MIYAPUR
HYDERABAD
500049.
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Gopi Raj, your question has been addressed before on this listserve.
Please search the archived messages for your answer.
Indranil Bhattacharya
DMPK
GlaxoSmithKline
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