Hi again , BluesBrother,
I have given a second thought to your question about niacin and the receptors you mention. If they are nicotinic receptors, chances are I did not find niacin in the list of agonist because it is too obvious, as nicotinic acid and niacin are quite bioequivalent. So, I think niacin is indeed an agonist of these receptors, meaning niacin activate them.
Niacin, anyway, is good for memory and cognition, which are helped by cholinergic activity, so niacin has cholinergic properties. This is still more obvious when considering that niacin deficiency leads to cognition problems and memory loss ( see
http://www.webmd.com/diet/niacin-deficiency-symptoms-and-treatments - note that this list is a mix of niacin and tryptophan deficiency symptoms, so you will find depression and apathy, among others, who are more related to tryptophan deficiency, which is absolutely needed for serotonin biosynthesis )
Not every POIS sufferer has low vagal tone. As I have already mentioned, I have a very high vagal tone in general. It is interesting, to say the least, that POIS never gave me any cognition and memory problems. Is it my high vagal tone that "protects" me from cognition problems , brain fog and memory loss ? I don'T know. If my way of seeing things is correct, vagal nerve stimulation would mostly relieve the cognition, brain fog and memory problems, what I call the pellagra-like and encenphalitis-like symptoms. My high vagal tone do not "protect" me from fatigue and from depression, apathy, fatigue, loss of self-esteem, and other psychological and emotional symptoms.... I am eager to see what symptoms will be relieved by vagal nerve stimulation in the Rutgers study. From my experience, I am not sure that emotional symptoms will be relieved by a higher vagal tone. But reality is more complex than we think... the study results may be very surprising to me ... I stay open to anything that will happen.