Fig. 5. Pharmacological assessment of the vasoactive intestinal polypeptide (VIP)-binding sites. Labelling of VIP-binding sites following treatment with different VPAC and PAC receptor agonists and antagonists. (A) Control, labelling of VIP-binding sites. (B) Labelling of VIP-binding sites following treatment with ckVIP. (C) Labelling of VIP-binding sites following treatment with the VIP receptor antagonist VIP 6-28. (D) Labelling of VIP-binding sites following treatment with the pituitary adenylate cyclase-activating polypeptide (PACAP) receptor agonist PACAP-27. (E) Labelling of VIP-binding sites following treatment with the PAC₁ receptor antagonist PACAP 6-27. Scale bars A–E, 150 µm.