title: Light- and electron-microscopic analysis of vasoactive intestinal polypeptide-immunoreactive amacrine cells in the guinea pig retina.
abstract: Vasoactive intestinal polypeptide (VIP) is a neuroactive substance that is expressed in both nonmammalian and mammalian retinas. This study investigated the morphology and synaptic connections of VIP-containing neurons in the guinea pig retina by immunocytochemistry, by using antisera against VIP. Specific VIP immunoreactivity was localized to a population of wide-field and regularly spaced amacrine cells with processes ramifying mainly in strata 1 and 2 of the inner plexiform layer (IPL). Double-label immunohistochemistry demonstrated that all VIP-immunoreactive cells possessed gamma-aminobutyric acid immunoreactivity. The synaptic connectivity of VIP-immunoreactive amacrine cells was identified in the IPL by electron microscopy. The VIP-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in strata 1 to 3 of the IPL. The most frequent postsynaptic targets of VIP-immunoreactive amacrine cells were other amacrine cell processes in strata 1 to 3 of the IPL. Synaptic outputs to bipolar cells were also observed in strata 1 to 3 of the IPL. In addition, ganglion cell dendrites were also postsynaptic to VIP-immunoreactive neurons in the sublamina a of the IPL. These studies show that one type of VIP-immunoreactive amacrine cells make contact predominantly with other amacrine cell processes. This finding suggests that VIP-containing amacrine cells may influence inner retinal circuitry, thus mediating visual processing.
authors.affiliation: Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Eun-Jin
authors.initials: EJ
authors.lastname: Lee
authors.forename: Sung-Hee
authors.initials: SH
authors.lastname: Park
authors.forename: In-Beom
authors.initials: IB
authors.lastname: Kim
authors.forename: Wha-Sun
authors.initials: WS
authors.lastname: Kang
authors.forename: Su-Ja
authors.initials: SJ
authors.lastname: Oh
authors.forename: Myung-Hoon
authors.initials: MH
authors.lastname: Chun
mesh_terms: D025042:Amacrine Cells / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D005260:Female; D006168:Guinea Pigs; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000502:physiology* / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D014660:Vasoactive Intestinal Peptide; D005680:gamma-Aminobutyric Acid