Stimulatory effects of pituitary adenylate cyclase-activating polypeptide on inositol phosphates accumulation in avian cerebral cortex and hypothalamus

Pituitary adenylate cyclase activating polypeptide plays a role in olfactory memory formation in chicken

PACAP plays an important role during development of the nervous system and is also involved in memory processing. The aim of the present study was to investigate the function of PACAP in chicken embryonic olfactory memory formation by blocking PACAP at a sensitive period in ovo. Chicken were exposed daily to strawberry scent in ovo from embryonic day 15. Control eggs were treated only with saline, while other eggs received a single injection of the PACAP antagonist PACAP6-38 at day 15. The consumption of scented and unscented water was measured daily after hatching. Animals exposed to strawberry scent in ovo showed no preference. However, chickens exposed to PACAP6-38, showed a clear preference for plain water, similarly to unexposed chicken. Our present study points to PACAP's possible importance in embryonic olfactory memory formation.

Receptors for vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in turkey cerebral cortex: characterization by [125I]-VIP binding and effects on cyclic AMP synthesis

Receptors for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) in turkey cerebral cortex were characterized using two approaches: (1) in vitro radioreceptor binding of [125I]-VIP, and (2) effects of peptides from the PACAP/VIP/secretin family on cyclic AMP formation. The binding of [125I]-VIP to turkey cortical membranes was rapid, stable, and reversible. Saturation analysis resulted in a linear Scatchard plot, suggesting binding to a single class of high affinity receptor binding sites with a Kd of 0.70 nM and a Bmax of 52 fmol/mg protein. Various peptides displaced the specific binding of 0.12 nM [125I]-VIP to turkey cerebral cortical membranes in a concentration-dependent manner. The relative rank order of potency of the tested peptides to inhibit [125I]-VIP binding to turkey cerebrum was: PACAP38 approximately PACAP27 approximately chicken VIP approximately mammalian VIP >>> PHI >> secretin, chicken VIP16-28 (inactive). About 65% of specific [125I]-VIP binding sites in turkey cerebral cortex was sensitive to Gpp(NH)p, a nonhydrolysable analogue of GTP. PACAP38, PACAP27, chicken VIP and, to a lesser extent, mammalian VIP potently stimulated cyclic AMP formation in turkey cerebral cortical slices in a concentration-dependent manner, displaying EC50 values of 8.7 nM (PACAP38), 21.3 nM (PACAP27), 67.4 nM (chicken VIP), and 202 nM (mammalian VIP). On the other hand, PHI and secretin very weakly affected the nucleotide production. The obtained results indicate that cerebral cortex of turkey contains VPAC type receptors that are positively linked to cyclic AMP-generating system and are labeled with [125I]-VIP.

Characterization of vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide receptors in chick cerebral cortex

In this study receptors for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) were characterized in chick cerebral cortex by an in vitro binding technique, using 125I-labeled VIP ([125I]-VIP) as a ligand. The specific binding of [125I]-VIP to chick cerebral cortical membranes was found to be rapid, stable, saturable, reversible, and of high affinity. Saturation analysis resulted in a linear Scatchard plot, suggesting binding to a single class of receptor binding sites with high affinity (Kd = 0.21 nM) and low capacity (Bmax = 19.5 fmol/mg protein). The relative rank order of potency of the tested peptides to inhibit [125I]-VIP binding to chick cerebrum was VIP (chicken) > or = VIP (mammalian) > or = PACAP27 > or = PACAP38 >> VIP6-28 (mammalian) > PHI (porcine) >> neurotensin6-11-chicken VIP7-28 > neurotensin6-11-mammalian VIP7-28 >>> VIP16-28 (chicken; inactive) approximately secretin (inactive). About 60% of [125I]-VIP-binding sites in chick cerebral cortex were sensitive to Gpp(NH)p, a nonhydrolyzable analog of GTP. It has been concluded that the cerebral cortex of chick, in addition to PAC1 receptors, contains a population of VPAC-type receptors.

PAC1 receptors in chick cerebral cortex: characterization by binding of pituitary adenylate cyclase-activating polypeptide, [125I]-PACAP27

In this study we characterized receptors for pituitary adenylate cyclase-activating polypeptide (PACAP) in chick cerebral cortex by in vitro binding technique, using [125I]-PACAP27 as a ligand. The specific binding of [125I]-PACAP27 to chick cerebral cortical membranes was found to be rapid, stable, saturable, and of high affinity. Scatchard analysis suggested binding to a single class of receptor binding sites with high affinity (K(d)=0.41+/-0.08 nM) and high capacity (B(max)=457+/-35 fmol/mg protein). The relative rank order of potency of the tested peptides to inhibit [125I]-PACAP27 binding to chick cerebrum was: PACAP38 approximately PACAP27>PACAP6-27 approximately PACAP6-38 >> chicken VIP >> mammalian VIP >> secretin (inactive). It is concluded that the cerebral cortex of chick, in addition to VPAC recognition sites, contains a large population of PAC(1)-type receptor binding sites.