Unfortunately, to my knowledge, there is still no commercially available adrenoceptor antibody that is proven specific. In 2009, a series of papers published in Naunyn Schmiedeberg’s Archives of Pharmacology reported that commercially available adrenoceptor antibodies are not specific:

Pradidarcheep, W. et al. Lack of specificity of commercially available antisera against muscarinergic and adrenergic receptors. Naunyn Schmiedebergs Arch. Pharmacol. 379, 397–402 (2009)

Hamdani, N. & van der Velden, J. Lack of specificity of antibodies directed against human beta-adrenergic receptors. Naunyn Schmiedebergs Arch. Pharmacol. 379, 403–407 (2009)

Jensen, B. C., Swigart, P. M. & Simpson, P. C. Ten commercial antibodies for alpha-1-adrenergic receptor subtypes are nonspecific. Naunyn Schmiedebergs Arch. Pharmacol. 379, 409–412 (2009)

See also cautionary note by Peter Kirkpatrick in Nature Reviews Drug Discovery 8(4):278.

In fact, Jensen et al. (cited above) concluded for α1-ARs:

"For now, competition radioligand binding is the only reliable approach to quantify the α1-AR subtype proteins."

Any further illumination of this issue by the RG community will be appreciated.