I personally think Muhammad was tripping (by substance or will) in the Hira cave.

When Muhammad met the angel Gabriel, it told him to recite this verse (often claimed to be the first thing composed for the Quran):

"Proclaim! (or read!) in the name of thy Lord and Cherisher, Who
Created man, out of a clot of congealed blood:
Proclaim! And thy Lord is Most Bountiful,–
Who taught by the pen–
Taught man that which he knew not." - [Quran 96:1-5]
I don't have a stake in the Anunnaki theory... but it fits the above verse...