Light- and electron-microscopic analysis of vasoactive intestinal polypeptide-immunoreactive amacrine cells in the guinea pig retina |
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Authors: | Lee Eun-Jin Park Sung-Hee Kim In-Beom Kang Wha-Sun Oh Su-Ja Chun Myung-Hoon |
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Institution: | Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea. |
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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. |
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Keywords: | vasoactive intestinal polypeptide immunocytochemistry synaptic connectivity retina guinea pig |
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