title: PACAP modulation of calcium ion activity in developing granule cells of the neonatal mouse olfactory bulb.
abstract: Ca(2+) activity in the CNS is critical for the establishment of developing neuronal circuitry prior to and during early sensory input. In developing olfactory bulb (OB), the neuromodulators that enhance network activity are largely unknown. Here we provide evidence that pituitary adenylate cyclase-activating peptide (PACAP)-specific PAC1 receptors (PAC1Rs) expressed in postnatal day (P)2-P5 mouse OB are functional and enhance network activity as measured by increases in calcium in genetically identified granule cells (GCs). We used confocal Ca(2+) imaging of OB slices from Dlx2-tdTomato mice to visualize GABAergic GCs. To address whether the PACAP-induced Ca(2+) oscillations were direct or indirect effects of PAC1R activation, we used antagonists for the GABA receptors (GABARs) and/or glutamate receptors (GluRs) in the presence and absence of PACAP. Combined block of GABARs and GluRs yielded a 66% decrease in the numbers of PACAP-responsive cells, suggesting that 34% of OB neurons are directly activated by PACAP. Similarly, immunocytochemistry using anti-PAC1 antibody showed that 34% of OB neurons express PAC1R. Blocking either GluRs or GABARs alone indirectly showed that PACAP stimulates release of both glutamate and GABA, which activate GCs. The appearance of PACAP-induced Ca(2+) activity in immature GCs suggests a role for PACAP in GC maturation. To conclude, we find that PACAP has both direct and indirect effects on neonatal OB GABAergic cells and may enhance network activity by promoting glutamate and GABA release. Furthermore, the numbers of PACAP-responsive GCs significantly increased between P2 and P5, suggesting that PACAP-induced Ca(2+) activity contributes to neonatal OB development.
authors.affiliation: Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah;
authors.forename: Mavis
authors.initials: M
authors.lastname: Irwin
authors.affiliation: Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah;
authors.forename: Ann
authors.initials: A
authors.lastname: Greig
authors.affiliation: Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah; Interdepartmental Neuroscience Program, University of Utah School of Medicine, Salt Lake City, Utah; and.
authors.forename: Petr
authors.initials: P
authors.lastname: Tvrdik
authors.affiliation: Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah; Interdepartmental Neuroscience Program, University of Utah School of Medicine, Salt Lake City, Utah; and Department of Neuroscience and Physiology, American University of the Caribbean, Cupecoy, Sint Maarten, Netherlands Antilles mlucero@aucmed.edu.
authors.forename: Mary T
authors.initials: MT
authors.lastname: Lucero
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D059330:GABAergic Neurons / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009830:Olfactory Bulb / Q000166:cytology / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000378:metabolism*; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002118:Calcium
keywords: PACAP; development; granule cell layer; olfaction