Regional heterogeneity of muscarinic acetylcholine receptors from rat brain is retained after detergent solubilization

Muscarinic acetylcholine receptors were extracted from rat cerebral cortex, hippocampus and brainstem membranes with 1% digitonin. Solubilized receptors retained both multiple receptor affinities and their regional selectivity in agonist binding (in terms of their affinity for carbamylcholine, brainstem>cortex>hippocampus). The affinity for carbamylcholine was increased 2–8-fold by solubilization; this increase was largely accounted for by an increase in the proportion of receptors displaying high affinity binding. No differences were observed in the size of receptor-detergent complexes from cortex or brainstem in gel filtration chromatography using a variety of gels and solubilizing agents. These findings indicate that not all of the factors underlying receptor heterogeneity and conformational state are removed or disrupted by solubilization.