Receptors for VIP and PACAP in guinea pig cerebral cortex: Effects on cyclic AMP synthesis and characterization by 125I-VIP binding

Jolanta B. Zawilska*, Agnieszka Dejda, Pawel Niewiadomski, Illana Gozes, Jerzy Z. Nowak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Receptors for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) in guinea pig cerebral cortex were characterized by (1) radioreceptor binding of 125I-labeled VIP (human/rat/porcine), and (2) cyclic AMP (cAMP) formation. Saturation analysis of 125I-VIP binding to membranes of guinea pig cerebral cortex resulted in a linear Scatchard plot, suggesting the presence of a single class of high-affinity receptor-binding sites, with a Kd of 0.63 nM and a Bmax of 77 fmol/mg protein. Various peptides from the PACAP/VIP/secretin family displaced the specific binding of 125I-VIP to guinea pig cerebrum with the relative rank order of potency: chicken VIP (cVIP) ≥ PACAP38 ≈ PACAP27 ≈ guinea pig VIP (gpVIP) ≥ mammalian (human/rat/porcine) VIP (mVIP) > peptide histidine-methionine (PHM) > peptide histidine-isoleucine (PHI) > secretin. Analysis of the competition curves revealed displacement of 125I-VIP from high- and lower-affinity binding sites, with IC50 values in the picomolar and the nanomolar range, respectively. About 70% of the specific 125I-VIP-binding sites in guinea pig cerebral cortex were sensitive to Gpp(NH)p, a nonhydrolyzable analog of GTP. Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38), PACAP27, cVIP, gpVIP, mVIP, PHM, and PHI stimulated cAMP production in [3H]adenine-prelabeled slices of guinea pig cerebral cortex in a concentration-dependent manner. Of the tested peptides, the most effective were PACAP38 and PACAP27, which at a 1 μM concentration produced a 17- to 19-fold rise in cAMP synthesis, increasing the nucleotide production to approx 11% conversion above the control value. The three forms of VIP (cVIP, mVIP, and gpVIP) at the highest concentration used, i.e., 3 μM, produced net increases in cAMP production in the range of 8-9% conversion, whereas 5 μM PHM and PHI, by, respectively, 6.7% and 4.9% conversion. It is concluded that cerebral cortex of guinea pig contains VPAC- type receptors positively linked to cAMP formation. In addition, the observed stronger action of PACAP (both PACAP38 and PACAP27), when compared to any form of VIP, on cAMP production in this tissue, suggests its interaction with both PAC1 and VPAC receptors.

Original languageEnglish
Pages (from-to)215-224
Number of pages10
JournalJournal of Molecular Neuroscience
Volume25
Issue number3
DOIs
StatePublished - Mar 2005

Funding

FundersFunder number
KBN502-13-856
Medical University of Lodz
Komitet Badań Naukowych

    Keywords

    • Guinea pig cerebral cortex
    • PACAP receptors
    • VIP receptors
    • cAMP

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