Early expression of pituitary adenylate cyclase-activating polypeptide and activation of its receptor in chick neuroblasts.
To investigate the involvement of pituitary adenylate cyclase- activating polypeptide (PACAP) and GH-releasing factor (GRF) during early chick brain development, we established neuroblast- enriched primary cell cultures derived from embryonic day 3.5 chick brain. We measured increases in cAMP generated by several species-specific forms of the peptides. Dose-dependent increases up to 5-fold of control values were measured in response to physiological concentrations of human/salmon, chicken, and tunicate PACAP27. Responses to PACAP38 were more variable, ranging from 5-fold for human PACAP38 to 4-fold for chicken PACAP38, to no significant response for salmon PACAP38, compared with control values. The responses to PACAP38 may reflect a greater difference in peptide structure compared with PACAP27 among species. Increases in cAMP generated by human, chicken, and salmon/carp GRF were not statistically significant, whereas increases in response to lower-range doses of tunicate GRF27-like peptide were significant, but small. We also used immunocytochemistry and Western blot to show synthesis of the PACAP38 peptide. RT-PCR was used to demonstrate that messenger RNAs for PACAP and GRF and a PACAP-specific receptor were present in the cells. This is a first report suggesting an autocrine/paracrine system for PACAP in early chick brain development, based on the presence of the ligand, messages for the ligand and receptor, and activation of the receptor in neuroblast-enriched cultures.
Department of Biology, University of Victoria, Victoria, British Columbia, Canada, V8W 2Y2.
N M
NM
Erhardt
E A
EA
Fradinger
L A
LA
Cervini
J E
JE
Rivier
N M
NM
Sherwood
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001921:Brain / Q000166:cytology* / Q000196:embryology*; D002642:Chick Embryo; D000242:Cyclic AMP / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000096:biosynthesis*; D010455:Peptides / Q000032:analysis / Q000138:chemical synthesis / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger / Q000096:biosynthesis; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018076:DNA, Complementary; D009479:Neuropeptides; D010455:Peptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone; D013007:Growth Hormone-Releasing Hormone; D000242:Cyclic AMP