Posted by sdb on April 11, 2005, at 16:29:41
In reply to Re: Hint for betablockers » mattw84, posted by ed_uk on April 11, 2005, at 13:25:20
Betablockers have influence on electrophysiological conduction and they also block beta1/beta2 or even alpha1 receptors on the cardiac tissue. Beta1/beta2 receptors play a role in the forwarding of electrical signals and there are more beta2 receptors on the heart tissue than it is often written in literature. Betablockers with
good beta2/beta1 blocking properties are the most effective to block the blunt adrenaline released by adrenal medulla. Electical conduction by nerves in the heart plays also a role in inotropie and chronotropie but this is more when you go swimming or jogging. Adrenaline is much more the trigger for inotropie and chronotropie in fight and flee situations.Interestingly betablocker molecules ressembles to adrenaline and as a consequence they block and stimulate at the same time (and this could cause beta downregulation, a positive effect of some betablockers in longterm use to combat fight and flight response).
Betablockers can also have membrane stabilizing actions (MSA), which could be an advantage for fight and flight responses (only in higher dosages). They modulate for example influx of fast Na channels.
Unfortunately it is true that beta1 blockers have less side effects than b1/2 blockers (beta2 receptores on blood vessels for example).
I would say that atenolol is a beta1/beta2 blocker with some more affinity to beta1-receptores and additional modulating properties in electrical conduction. Thus there is some efficacy in higher dosages for fight and flight situations. Unfortunately there is documented beta-receptor upregulation with time and this is a disadvantage for longterm use to combat anxiety response.
Most effective b1/b2 blockers are
Bopindolol, pindolol, timolol (mostly used by oculists), nadolol, oxprenolol, propranololkind regards
sdb
poster:sdb
thread:482260
URL: http://www.dr-bob.org/babble/20050408/msgs/482924.html