How does cannabis itself work in the pineal gland?

Research on rats has shown that the pineal gland contains a functional endocannabinoid system,
in that cannabinoid receptors type 1 and 2, and the endogenous ligands
that bind to them, anandamide and 2-AG, are all present.

The study showed that the activity of the CB?-receptors varied
according to a daily cycle, with lowest activity levels occurring at the
end of the daylight period. It also showed that levels of an enzyme
responsible for synthesizing new endocannabinoid molecules, NAPE-PLD,
was reduced during the middle of the dark period.

Furthermore, the study showed that presence of THC reduced the
activity of an enzyme known as AANAT, and in doing so reduces the
synthesis of melatonin itself. An earlier study on rats
also showed that THC reduced the activity of AANAT, and suggested that
the mechanism that occurred was as follows: the neurotransmitter
norepinephrine starts a cascade of reactions, the end result of which is
the production of melatonin. THC disrupts this norepinephrine cascade
and thereby reduces the production of melatonin.

It is likely that THC’s endogenous analogue anandamide performs the
same action of reducing the norepinephrine-induced release of melatonin,
and is therefore fundamentally involved in pineal gland function. It
seems that low levels of anandamide or THC are therefore needed in order
for melatonin production to increase. As melatonin levels increase, as
they should normally do at the end of the daylight period, feelings of
sleepiness should occur.