Altered psychomotor behaviors in mice lacking pituitary adenylate cyclase-activating polypeptide (PACAP)

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been conserved remarkably during evolution and is widely expressed in the mammalian brain. In Drosophila, mutation of the PACAP homologue results in behavioral defects, including impaired olfaction-associated learning and changes in ethanol sensitivity. Here, we report the generation of mice lacking the PACAP gene (PACAP(-/-)). PACAP(-/-) mice were born in the expected Mendelian ratios but had a high early-mortality rate. The surviving adult PACAP(-/-) mice displayed remarkable behavioral changes; they exhibited hyperactive and explosive jumping behaviors in an open field, increased exploratory behavior, and less anxiety in the elevated plus maze, emergence, and novel-object tests. Analysis of PACAP(-/-) mice brains revealed that the serotonin metabolite 5-hydroxyindoleacetic acid was slightly decreased in the cortex and striatum compared with wild-type mice. The present study provides evidence that PACAP plays a previously uncharacterized role in the regulation of psychomotor behaviors.

Desensitization, surface expression, and glycosylation of a functional, epitope-tagged type I PACAP (PAC(1)) receptor

To study desensitization and glycosylation of the type I pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PAC(1)R), a hemagglutinin (HA) epitope was inserted within the N-terminal extracellular domain, allowing immunological detection of PAC(1)R both in intact and permeabilized cells. PAC(1)R was tagged without loss of functions in ligand binding and ligand-stimulated cAMP production. In transiently transfected COS-7 cells, PAC(1)R was localized both in the plasma membrane and the cytoplasm around the nucleus. By immunoblot analysis, the immunoreactive bands with relative molecular masses ranging from 45 to 70 kDa were detected in the membrane fractions of PAC(1)R-expressing COS-7 cells. Digestion of the membranes with endoglycosidase F or treatment of the cells with tunicamycin decreased the size of the receptor to major bands of smaller size (approximately 45 and 48 kDa), suggesting that these two forms of PAC(1)R represent core proteins. Flow cytometric analysis indicated that the agonist promoted a disappearance of cell surface receptor. In accordance with this observation, preexposure of cells to PACAP38 induced a desensitization of PAC(1)R to the agonist response, although it did not cause a reduction in PAC(1)R mRNA or protein level and even slightly elevated them. These results suggest that agonist-induced desensitization of PAC(1)R involves the receptor sequestration.