Receptor d-reg permanent with clen?

Hey everyone... I've been researching clen extensively, but from everything i read I could only find anecdotal evidence on Clen and receptor downregulation.
I was wondering if anyone knows any studies or can cite some scientific logic as to what happens when the beta-2 receptors are downgraded as a result of clenbuterol use?
I think that in time these receptors upregulate again but I'm not sure and i don't know how much time this takes or how this process happens...
Also, does anyone know what could happen if these receptors downregulate, could this produce pulmonary side effects in users such as trouble breathing or some forms of asthmatic conditions?

Thanx a lot bros...

The receptors will recover after a period of about two weeks. That is why people cycle two weeks on, two weeks off. Search for the Clenbuterol Handbook, in this forum.