Are all Autoreceptors Downregulated by their Respective Endogenous Ligands?

[Ganesh Ujwal]

I know that the [latex]5HT_{1A}[/latex] and α2 adrenoreceptors receptors serve as autoreceptors for serotonin (5-HT) and norepinephrine respectively and are down-regulated by repeat exposure to their respective ligands, it's believed that this is likely the cause for the therapeutic delay in the actions of antidepressants that target the serotonergic and noradrenergic systems. My question is this: "Is this the case for all autoreceptors? Are all autoreceptors down-regulated by the actions of their respective ligands?"

Edited December 13, 2014 by Ganesh Ujwal