Vasoconstriction in Hemostasis

[Cheman]

In hemostasis there is an initial vasoconstriction as a result of a nervous reflex. This lasts less than one minute. However, vasoconstriction still occurs during coagulation as a result of released chemicals, eg - serotonin released in the platelet granuales. Now, there are two ways that chemical such as serotonin could lead to vasoconstriction and I was just wondering if anyone could tell me which one it is.
Does release of serotonin:
1) Lead to a nervous response which leads to vasoconstriction (as nerves are usually the cause of muscular contraction), or
2) Directly cause vasoconstriction, rather than it being a nervous response?
I have my own idea as to which one I believe it is, but does anybody actually know?
Thanks in advance. :-)

[Cheman]

Go on - somebody must know. :wink: Basically, all I want to know is whether the vasoconstriction in haemostasis is purely due to the chemicals released (eg - serotin) or the chemicals initiating a nervous response which causes vasoconstriction.
Thanks.

[fafalone]

Well I'll take a guess and say it's a related directly to intercellular serotonin concentration since SRIs have been demonstration to create vasoconstriction.