Presynaptic terminal A has 10 voltagegated Ca2 channels Cav

Presynaptic terminal A has 10 voltage-gated Ca2+ channels (Cav). Presynaptic terminal B has 15 Cav. All other things being equal, which presynaptic terminal would have a higher release probability (Pr)?

Solution

Answer:

Release probabilty is determined by the calcium influx through voltage gated calcium channels near to a release site. Expression of increased amount of voltage gated calcium channels results in enhanced release probability which is mutually exclusive of the trafficking.

Considering a simplistic model, the number of voltage gated calcium channels in presynaptic terminal A is 10 which is less than the presynaptic terminal B which has 15. This results in a higher calcium influx in presynaptic terminal B. So, the release probability is higher in presynaptic terminal B than presynaptic terminal A.