In primary cultures of cerebellar granule cells, an antisense strategy was used to elucidate the structure and function of GABAB receptors that inhibit adenylyl cyclase activity. The muscarinic m2 receptor, also expressed in cerebellar granule cell cultures, was the positive control determining the effectiveness of the antisense strategy. Three antisense oligodeoxynucleotides were constructed: antisense 7TMR (a 15-mer targeted to the region of mRNA encoding the second transmembrane spanning domain common to the family of G-protein-coupled receptors) and antisense βARK- 1 and βARK-2 (both 15-mers targeted to two different coding regions of the mRNA encoding for β-adrenergic receptor kinase). Using radlolabeled antisense oligonucleotides, all were shown to enter the cells being detected intact even after a 24-h application. At 25 μM, antisense 7TMR completely inhibited the muscarinic m2 receptor-mediated response while partially decreasing the GABAB receptor-mediated response, suggesting that the GABAB receptor may have the common second transmembrane spanning domain. Antisense βARK-1 and βARK-2 prevented the desensitization of the m2 receptor via βARK, but did not change the sensitivity of the GABAB receptor. Thus, the use of antisense oligonucleotides in the presence of a positive control is a useful technique in further characterizing the biochemical structure and physiological function of proteins.