Histamine And His Role In Sleep/wake And AD(H)D

[Kasper]

Wow, I've been studying histamine for some time, and it's quite interesting, but so hard ! Please correct me if I'm wrong, I'm kind of noob with biology and pubmed, and I'm sure I make mistakes all the time.

Histamine in the hypothalamus seems to have some role in regulating sleep wake cycles. In rats it seems to be highest at one hour after the light went on, and lowest one hour after the lights turned off.

Twenty-four hour rhythms of histamine (H), its biosynthetic enzyme, L-histidine decarboxylase (EC 4.1.1.22, HD) and its inactivation enzyme, histamine N-methyltransferase (EC 2.1.1.8, HMT) were assayed in the 63-day-old male rat hypothalamus using a modified single isotopeenzyme microassay. H was found to have a 24-h rhythm with a maximum concentration at 11:00 h (lights on 10:00-22:00 h) and a minimum at 23:00 h.

I find this interesting as I feel dreamy during the day without medication. And this medication works by increasing histamine in the hypothalamus.
It's been known that people with ADHD produces quite more brain waves (gamma and delta waves) that are associated with (deep) sleeping, during the day.
I guess that maybe increasing histamine in the hypothalamus makes sure people mainly have alpha/beta brain waves that are more associated with feeling awake.

But, if I read Ray Peat, he seem to think that histamine is little bit like estrogen. Maybe histamine in the brain and histamine from mast cells have really different functions ? I don't know. But I don't think it is bad thing to feel awake during the day ! :P

Consequently, mice that lack brain histamine are unable to remain awake when high vigilance is required, e.g., at lights off or when they are placed in a new environment (Parmentier et al., 2002). Together, these results indicate that histaminergic neurons have a key role in maintaining the brain awake under normal conditions and in the presence of behavioral challenges. They promote wakefulness through their direct widespread projections to the cerebral cortex and indirectly via their subcortical targets in the thalamus, basal forebrain and brainstem (Lin et al., 1996b).