Faintness after inserting dildo deep anally

A couple of days ago I wanted to have some fun with my home made 16" dildo. Like many other times I just cleaned out my intestines with some plain water and proceeded to insert the dildo. I could eventually insert the whole length of the dildo and it felt great; I slid it in and out a few times and was really enjoying it but after a while I started feeling light headed and kind of hot in the face; I stopped immediately, got some fresh air, drank and splashed my face with some cold water and sat down for a few minutes; I thought I was going to pass out but eventually I came round; I checked for blood or any unusual pain but everything seemed fine. I couldn't measure my blood pressure but the pulse was normal.

Did anyone ever experience "side effects" after an enema or anal stimulation? This is the first time it happened to me.

I have experienced some sort of light headiness (is that correct spelling?) by deep stimulation, and I read somewhere (on this site?) that is because of stimulation of vagus nerve. Please check out the following:

http://en.wikipedia.org/wiki/Vagus_nerve

especially the "Physical and emotional effects" section

Thanks, afternine. The link you added is very interesting and I think it explains it pretty well.