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+--- Thread: plz. help me clear a very basic concept - dbhansali (/showthread.php?tid=216386)
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plz. help me clear a very basic concept - dbhansali - ArchivalUser - 09-05-2007
When beta receptor are activated, they result in fall of blood pressure, then how come beta receptor anatgonists are used as antihypertensives (they should be increasing BP)
I know its a very basic concept, but somehow Im loosing it. Plz. clarify
0 - ArchivalUser - 09-05-2007
beta 2 causes fall in blood pressure by reducing tpr while beta 1 antagonism decreses heart contraction and reduces blood pressure???
0 - ArchivalUser - 09-05-2007
so do beta 1 by themselves increase blood pressure
0 - ArchivalUser - 09-05-2007
B-1 activation---------inc. HR,contractility--- inc.CO----Inc. BP
inc. renin release---INc BP
B-2 activation--------vasodilatation----------Dec.BP
Most of the anti hpertensives Has selective B1antagonistic function or if both then predominant B-1 antagonist action.
hope this might help.
0 - ArchivalUser - 09-05-2007
they do increase cardiac output...dopamine and dobutamine are used through them isn`t it? and cardiac output increase leads to increase in bp.
this is the mech as far as i know.
0 - ArchivalUser - 09-05-2007
Can you be bit explanatory of your version.
0 - ArchivalUser - 09-05-2007
nad i`ve read somewhere that the beta blockers initially cause a mild tachycardia understandably but wih continued administration there is tolerance and the baroreceptor setting and all whch keads to beta 1 action predoinance..
0 - ArchivalUser - 09-05-2007
gr8 thnk u guys. It makes me feel much better
0 - ArchivalUser - 09-05-2007
hi raj_
i was answering drbhansali`s question-whether beta 1 increases blood pressure by themselves
0 - ArchivalUser - 09-05-2007
Yaa you are right B-2 receptors will be unresponsive over a period of continious stimulation
but not B-1. There is aterm also for this mechanism I dont remember it.