“…Most of the structure-activity relationship studies focusing on type II receptor so far have been carried out with VIP derivatives and have contributed to the development of pharmacological tools that discriminate between VPAC1-R and VPAC2-R (Table 4) (Robberecht et al, 2003;Laburthe and Couvineau, 2002;Laburthe et al, 2003;Couvineau et al, 2006). N-terminally truncated analogs of PACAP show a preference for VPAC2-R. For instance, the PACAP(6 -38) fragment exhibits a 15-fold higher affinity for VPAC2-R than for VPAC1-R (Gourlet et al, 1995), whereas PACAP(1-25) possesses a 66-fold higher affinity for VPAC1-R than for VPAC2-R .…”