Earlier quoted context omitted.
The loss of inhibition is culturally learned, not biochemical. You can relax and let loose because society judges you less harshly when drunk (and, if you have internalized it, you judge yourself less harshly too). In some cultures it's not present at all, and even in some you may visit it's much weaker. Be aware of this if you get drunk as a tourist.
This doesn't make sense to me. Alcohol binds to the GABA receptor mimicking GABA, hence providing a calming feeling. It allows people to feel less anxious in situations they might normally feel awkward. That is definitely not cultural. Drinking regularly may desensitize your GABA receptors and hence cause a person to end up with more anxiety as a result of drinking. I rarely drink because I found it was exasperating…
Even emotional states such as happy, calm, afraid etc. are higher level phenomena that don't map nicely onto hormones and neurotransmitters. The same low-level signal may even be interpreted in different ways depending on circumstance. There's a classic experiment with niacin demonstrating this, but like so many old behaviour experiments, it's ignored in favour of more "white coat" neuroscience these days.