NIH/3T3 cells stably expressing the indicated hPAC1 NullWT, NullTr406, and NullTr433 (A) and hPAC1 HopWT, HopTr406, and HopTr433 (B) were incubated with 50 pM of 125I-PACAP-27. At the indicated time intervals, cells were subjected to a 0.5 M KSCN solution. Internalized radioligand is defined as 125I-PACAP-27 that could not be stripped by KSCN and is expressed as a percentage of the total saturable bound 125I-PACAP-27 in control cells, processed in parallel without KSCN exposure. Each value represents the means of at least three experiments performed in triplicate.