Cannabinoid receptors on goldfish retinal bipolar cells: electron-microscope immunocytochemistry and whole-cell recordings.
Cannabinoid CB1 receptors are distributed throughout the CNS and interact with GABA, glutamate, and dopamine systems. Cannabinoids have effects on the visual system, some of which may have a retinal component, particularly the enhancement of photosensitivity. We used immunocytochemistry and whole-cell recording to study cannabinoids in the goldfish retina. Immunoblots of an antiserum against amino acids (1-14) of the rat CB1 receptor produced a single band in goldfish retina at about 70 kDa. Light microscope immunocytochemistry of CB1 receptor immunoreactivity (CB1R-IR) revealed intense staining of Müller cells and weaker staining of ON bipolar cells (verified with double labeling with PKC-IR) and the outer and inner plexiform layers. Ultrastructural analysis revealed that CB1R-IR was localized intracellularly as well as on the plasma membrane of photoreceptor terminals, bipolar cell terminals and, rarely, amacrine cell boutons. Membrane-associated CB1R-IR was restricted to cone pedicles at sites removed from the synaptic ribbon. Regarding bipolar cells, membrane-associated CB1R-IR was found at 93% of the synaptic terminals in sublamina b (ON-type) and only at 33% of the synaptic terminals in sublamina a (OFF-type). Whole-cell recordings from large ON-type Mb bipolar cells showed that the delayed rectifier (I(K(V))) was rapidly and reversibly inhibited by 1 microM of the cannabinoid agonists CP 54490 and (+)-WIN 55212-2, effects blocked completely by the antagonist SR 141716A (1 microM). Inhibition of I(K(V)) in the Mb bipolar cells by cannabinoids should result in a more tonic ON response to increments of light. As such, cannabinoids may play a role in modulating the temporal aspects of signaling in the retina.
Department of Neurobiology and Behavior, University at Stony Brook, NY 11794-5230, USA. yazulla@life.bio.sunysb.edu
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D000818:Animals; D000911:Antibodies, Monoclonal; D048588:Benzoxazines; D002186:Cannabinoids / Q000819:agonists / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003511:Cyclohexanols / Q000494:pharmacology; D004594:Electrophysiology; D019084:Fluorescent Antibody Technique, Indirect; D006054:Goldfish / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D010880:Piperidines / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D011720:Pyrazoles / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000378:metabolism*; D000077285:Rimonabant
D000911:Antibodies, Monoclonal; D048588:Benzoxazines; D002186:Cannabinoids; D003511:Cyclohexanols; D009025:Morpholines; D009281:Naphthalenes; D010880:Piperidines; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D000077285:Rimonabant