Polyclonal antibodies raised to synthetic amino acid sequences of the rat gamma-aminobutyric acid (GABAA) receptor alpha 1-, alpha 2- and alpha 3-subunits selectively recognized single proteins with apparent molecular weight 51 kDa (P51), 53 kDa (P53) and 59 kDa (P59), respectively, in GABAA receptor preparations affinity purified from the brains of 5-10-day-old rats. The antibodies were coupled to Affigel 10, and the resulting immunoaffinity columns were used to isolate these proteins from affinity purified GABAA receptors.