Posted by undopaminergic on April 3, 2008, at 22:04:23
In reply to Re: High BP on Selegiline! B-Blockers, good?, posted by Amigan on April 3, 2008, at 16:06:01
>
> > Probably a beta blocker would be the best drug to try to prevent the increase in blood pressure due to norepinephrine.
>
> how sure are you about this? From what i have read, beta blockers can have exactly the opposite results in the present of a sympathomimetic factor and perhaps in cases of excessive NE, too.
> The Beta receptors in blood vessels are responsible for vasodilation, while the Alpha receptors for vasoconstriction. THUS, if you block the B receptors, while the Alpha ones remain stimulated by the excessive N,NE or the SM factor, you have an increase in blood pressure.
>Beta2-adrenoceptors mediate many of the (usually) desirable effects of adrenaline - including vasodilation, bronchodilation, and reduction of allergic responses, although they also increase heart rate, and their improvement of muscular blood flow may have undesirable side-effects (e.g. tremor). Selective beta1-adrenergic antagonists ("cardioselective" beta-blockers) should leave the beta2-receptors alone, but their primary effect is to reduce heart rate, which will reduce blood pressure, but not reverse the effects of vasoconstriction caused by selegiline-induced noradrenaline release (assuming that is the cause of your elevated BP).
An interesting (but unrelated) question is the psychoactive effects of beta-blockers (some of them cross the blood-brain-barrier easily), and more generally, the role of beta-receptors in the brain.
poster:undopaminergic
thread:819397
URL: http://www.dr-bob.org/babble/20080330/msgs/821477.html