An in vitro study of retinotectal transmission in the chick: Role of glutamate and GABA in evoked field potentials
| Autor: | Harvey J. Karten, J. C. Dye |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Retinal Ganglion Cells
Superior Colliculi Physiology Glutamic Acid In Vitro Techniques Biology Inhibitory postsynaptic potential Synaptic Transmission chemistry.chemical_compound Slice preparation Postsynaptic potential Quinoxalines medicine Animals Visual Pathways gamma-Aminobutyric Acid 6-Cyano-7-nitroquinoxaline-2 3-dione Bicuculline GABA receptor antagonist Electric Stimulation Sensory Systems 2-Amino-5-phosphonovalerate chemistry CNQX Excitatory postsynaptic potential Evoked Potentials Visual NMDA receptor Chickens Excitatory Amino Acid Antagonists Neuroscience medicine.drug |
| Zdroj: | Visual Neuroscience. 13:747-758 |
| ISSN: | 1469-8714 0952-5238 |
| DOI: | 10.1017/s0952523800008622 |
| Popis: | We have developed two brain slice preparations for studying tectofugal visual pathways in the chick: conventional, 400-μm slices (“thin slices”), and “thick slices” which encompass the rostral pole of the optic tectum and the contralateral optic nerve. Stimulation was delivered with a bipolar electrode positioned in stratum opticum in thin slices and in the contralateral optic nerve in thick slices. While the latter preparation provided a means of exclusively and unambiguously activating retinal afferents, several lines of evidence also indicated that the evoked field potentials in thin slices were chiefly consequent to retinal afferent excitation: (1) the similarity of evoked field potentials in thin slices to those in thick slice preparations; (2) their precise localization in retinorecipient layers as shown by prelabeling from retina with FITC-coupled cholera toxin; (3) transmission delays appropriate for retinal afferents as established with the thick slice preparation; (4) patterns of labeled afferents resulting from applications of Dil crystals to slices fixed after recording; and (5) the similarity in transmitter pharmacology between thin and thick slice preparations. Pharmacological manipulations carried out with bath-applied antagonists indicated that glutamate is the principal retinotectal transmitter. The broadly active glutamate receptor blocker, kynurenic acid, reversibly eliminated the postsynaptic component of the field potential as confirmed with 0 Ca2+ saline. A complete block was also effected by the non-NMDA antagonists CNQX and DNQX. The specific NMDA antagonist, APS, caused a smaller and variable reduction in response amplitude. The GABA antagonist, bicuculline, caused a prolongation of the monosynaptic field epsp in retinorecipient layers and an enhancement of the long-latency, negative wave in cellular layers below, supporting a late, excitation-limiting role for this inhibitory transmitter. |
| Databáze: | OpenAIRE |
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