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Cannabinoid receptors on goldfish retinal bipolar cells: Electron-microscope immunocytochemistry and whole-cell recordings

Published online by Cambridge University Press:  01 May 2000

STEPHEN YAZULLA ,
KEITH M. STUDHOLME ,
HELEN H. McINTOSH  and
SHIH-FANG FAN
STEPHEN YAZULLA
Affiliation:
Department of Neurobiology and Behavior, University at Stony Brook, Stony Brook, NY
KEITH M. STUDHOLME
Affiliation:
Department of Neurobiology and Behavior, University at Stony Brook, Stony Brook, NY
HELEN H. McINTOSH
Affiliation:
Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, MO
SHIH-FANG FAN
Affiliation:
Department of Neurobiology and Behavior, University at Stony Brook, Stony Brook, NY
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Abstract

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 (IK(V)) was rapidly and reversibly inhibited by 1 μM of the cannabinoid agonists CP 54490 and (+)-WIN 55212-2, effects blocked completely by the antagonist SR 141716A (1 μM). Inhibition of IK(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.

Keywords

CannabinoidRetinaBipolar cellEicosanoidPotassium channels
Type
Research Article
Information
Visual Neuroscience , Volume 17 , Issue 3 , May 2000 , pp. 391 - 401
Copyright
2000 Cambridge University Press

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