Detection of low level histamine H3 receptor occupancy by autoradiography.
Histamine H(3) receptor antagonists have been proposed as a novel approach to the treatment of cognitive, attentional, and sleep disorders. It is apparent that H(3) receptor antagonists produce in vivo effects in preclinical animal models of central diseases across a wide dose range. In order to characterize the relationship between efficacy in the preclinical models and H(3) receptor occupancy, a brain slice receptor autoradiography method was used. Brain slice receptor autoradiography requires less in vitro tissue processing, preserves brain structure, and provides anatomical localization of compound in the brain. Consistent with H(3) receptor distribution, in vitro autoradiography experiments demonstrated specific binding of [(3)H]NAMH (N-alpha-methylhistamine) in rat cortex, and other brain regions, but not in cerebellum. Ex vivo H(3)R brain slice autoradiography was able to detect H(3) receptor occupancy by reference antagonists at doses lower than previously found using a homogenate assay format. The method is relatively quick with image acquisition on a beta-imager and is capable of detecting receptor occupancy in different brain regions simultaneously. Furthermore, the increased sensitivity should be useful in providing dosing guidelines for H(3) antagonists in both preclinical and clinical settings.
Le
Siyuan
S
World Wide Discovery Research, Cephalon, Inc., West Chester, PA 19380, USA. sle@cephalon.com
Finn
James P
JP
Larijani
Mary E
ME
Marino
Michael J
MJ
Schaffhauser
Hervé
H
D000818:Animals; D001345:Autoradiography / Q000379:methods*; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001681:Biological Assay; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D001923:Brain Chemistry / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006633:Histamine Antagonists / Q000032:analysis* / Q000378:metabolism; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D009924:Organ Culture Techniques; D011237:Predictive Value of Tests; D051381:Rats; D017207:Rats, Sprague-Dawley; D018100:Receptors, Histamine H3 / Q000187:drug effects* / Q000378:metabolism; D012016:Reference Values; D012680:Sensitivity and Specificity
D006633:Histamine Antagonists; D018100:Receptors, Histamine H3