title: Protein kinase A modulates retinal ganglion cell growth during development.
abstract: During development, retinal ganglion cells (RGCs) extend their axons toward their thalamic and mesencephalic targets. Their navigation is largely directed by guidance cues present in their environment. Since cAMP is an important second messenger that mediates the neural response to guidance molecules and its intracellular levels seem to decrease significantly following birth, we tested whether modulation of the cAMP/protein kinase A (PKA) pathway would affect the normal development of RGC axons. At postnatal day 1, hamsters received a unilateral intraocular injection of either 0.9% saline solution, 12 mM of the membrane-permeable cAMP analogue (dibutyryl cAMP; db-cAMP), or 10 microM of the PKA inhibitor KT5720. Intraocular elevation of cAMP significantly accelerated RGC axonal growth while inhibition of PKA activity decreased it. Moreover, when highly purified RGC cultures were treated with forskolin (an activator of adenylate cyclase) or cAMP analogues (db-cAMP and Sp-cAMP), neurite length, growth cone (GC) surface area and GC filopodia number were significantly increased. This indicates that intraocular elevation of cAMP acts directly on RGCs. Since these effects were prevented by PKA inhibitors, it demonstrates that cAMP also exerts its action via the PKA pathway. Taken together, these results suggest that the cAMP/PKA cascade is essential for the normal development of retinothalamic projections.
authors.affiliation: Department of Biomedical Science, Faculty of Medicine, University of Montreal, Montreal, Quebec, Canada H3T 1J4.
authors.forename: Anteneh
authors.initials: A
authors.lastname: Argaw
authors.forename: Gabriel
authors.initials: G
authors.lastname: Duff
authors.forename: Denis
authors.initials: D
authors.lastname: Boire
authors.forename: Maurice
authors.initials: M
authors.lastname: Ptito
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Bouchard
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D008647:Mesocricetus; D051379:Mice; D011758:Pyrroles / Q000494:pharmacology; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002227:Carbazoles; D011758:Pyrroles; C057416:KT 5720; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases