hyperpolarization of smooth muscle --> vasodilation?

[MudPhud20XX]

While I was going over Kaplan pharm "Direct-Acting Vasodilators, Drugs Acting Through NO and to Open Potassium Channels," I came up with some questions:

1. Hydralazine selectively dilate arteriole not veins, can anyone explain why? Why doesn't it work for venous dilation? On the other hand, nitrate actually works on venous dilation yet these two drugs work though nitric oxide pathway, right? Can anyone help me out?

2. Can anyone explain why hyperpolarization of smooth muscle result in vasodilation? I guess the question I want to ask is why does hyperpolarization of smooth muscle make the muscle relaxed?

3. Also, can anyone explain why drugs such as minoxidil and diazoxide are selective arteriolar vasodilation? Is it simply the fact that you find more smooth muscle in arteries?

Many thanks in advance.

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[notbobtrustme]

hyperpolarized smooth muscle can't contract (since APs are needed to release calcium from SR to activate calmodulin and activation of myosin light chain), ergo, they are relaxed, leading to vasodilation.

no idea about the rest, but probably has to do with specific receptors or some ****

edit: quick google-fu kind of supports that half-assed statement. arteriolar dilators can dilate veins at higher doses while venous dilators (eg NO) can dilate arteries at higher doses.