Alpha 1 receptors are located in- Eye radial (i.e dilator) muscle Arterioles and viens, Male sex oegans, Urinary bladder, Kidney and Liver. Alpha 1 receptors use G q Coupled secondary mediators and cause increase in phospholipase C, IP3, DAG and calcium levels in the cell. Alpha1 blockers: Selective Blockers- Prazosin, Doxazocin, Terazocin Non selective Alpha blockers (both alpha 1 and alpha 2 receptor blockers)- Phentolamine(competitive inhibitor), Phenoxybenzamine (non competitive inhibitor) Effects of Alpha1 receptor blockage: Eye- Miosis Arterioles and veins- Reduced sympathetic tone in blood vessels- This results in vasodilation, Decrease in preload and after load on heart, lowering of peripheral vascular resistance and thus a fall in blood pressure is noted. The drop in blood pressure causes a reflex tachycardia. Prazosin : Prazosin can lower BP rapidly so patients are recommended to relax for 1 hour after taking the first dose and
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