First, based on the quantities of individual BK transcripts encoding individual splice variant monomers (Figure 2), we calculated the probabilities of all possible combinations of monomers assembled into tetramers in both SON and striatal neurons (Equation 1, Methodology). We determined that in naive SON neurons four types of tetramer were most prevalent: ALCOREX/INSERTLESS heteromers (almost half of the total amount of the channel), INSERTLESS homomers (about one third), INSERTLESS/STREX heteromers and ALCOREX/INSERTLESS/STREX heteromers (each about 10% of total amount) (Figure 7A).
