title: Coordinated transitions in neurotransmitter systems for the initiation and propagation of spontaneous retinal waves.
abstract: Spontaneous waves of excitation in the developing mammalian retina are mediated, to a large extent, by neurotransmission. However, it is unclear how the underlying neurotransmitter systems interact with each other to play specific roles in the formation of retinal waves at various developmental stages. In particular, it is puzzling why the waves maintain a similar propagation pattern even after underlying neurotransmitter systems have undergone drastic developmental changes. Using Ca(2+) imaging and patch clamp in a whole-mount preparation of the developing rabbit retina, we discovered two dramatic and coordinated transitions in the excitatory drive for retinal waves: one from a nicotinic to a muscarinic system, and the other from a fast cholinergic to a fast glutamatergic input. Retinal waves before the age of postnatal day 1 (P1) were blocked by nicotinic antagonists, but not by muscarinic or glutamatergic antagonists. After P3, however, the spontaneous wave, whose basic spatiotemporal pattern remained similar, was completely inhibited by muscarinic or glutamate antagonists, but not by nicotinic antagonists. We also found that the muscarinic drive, mediated primarily by M1 and M3 receptors, was particularly important for wave propagation, whereas the glutamatergic drive seemed more important for local excitation. Our results suggest (1) a novel mechanism by which a neurotransmitter system changes its functional role via a switch between two completely different classes of receptors for the same transmitter, (2) the cholinergic system plays a critical role in not only early but also late spontaneous waves, and (3) the continued participation of the cholinergic system may provide a network basis for the consistency in the overall propagation pattern of spontaneous retinal waves.
authors.affiliation: Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. zhoujimmy@exchange.uams.edu
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Zhou
authors.forename: D
authors.initials: D
authors.lastname: Zhao
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology*; D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D001285:Atropine / Q000494:pharmacology*; D002038:Bungarotoxins / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D003472:Curare / Q000494:pharmacology*; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D018738:Hexamethonium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009116:Muscarine / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D011817:Rabbits; D012160:Retina / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology*
chemical_list: D002038:Bungarotoxins; D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D018727:Muscarinic Antagonists; D018377:Neurotransmitter Agents; D018733:Nicotinic Antagonists; D010880:Piperidines; C049925:fura-2-am; D018738:Hexamethonium; D004246:Dimethylphenylpiperazinium Iodide; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D001285:Atropine; D009116:Muscarine; D003472:Curare; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D002118:Calcium; D016257:Fura-2