Role of ON and OFF Visual Pathways in Rod- and Cone-Driven Flicker Responses

Purpose: To evaluate the effects of various retinal neurotransmitters on temporal resolution, particularly, on the Critical Flicker Fusion Frequency (CFF), which has been previously applied in ophthalmic pathophysiologic research.

Methods: A binocular physiologic electroretinogram was performed on adult mice. Animals in the control group were injected in the right eye with 1 μL of phosphate-buffered saline (PBS). Animals in the experimental group were injected in the left eye with 1 μL of PBS and in the right eye with 1 μL of PBS to which different molecules were added: 2-amino-4-phosphonobutyric acid (APB), Glutamate, γ-aminobutyric acid (GABA), 6,7-dinitroquinoxaline-2,3-dione (DNQX), Bicuculline, Glycine, and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). Initially, rod response was recorded and later the cone response.

Results: APB suppressed the rod-driven, but not the cone-driven flicker response. The other agents severely affected the lower flickering frequency response amplitude, in particular, at 3 Hz. The threshold of CFF was lowered from 50 Hz to 40 Hz after applying APB, Glycine, and HEPES. GABA remarkably enhanced rod-driven and cone-driven flicker response at 3 Hz, whereas Glutamate and GABA/Glutamate only did in rod-driven flicker response.

Conclusions: Both ON and OFF visual pathways were implied in cone-driven response, but only the ON visual pathway appears to play a relevant role in rod-driven flicker response. Flicker response seems to be enhanced by horizontal cells both in rod-driven and cone-driven response. In addition, due to the greater sensitivity of the flicker at low frequencies, it is suggested that pathophysiological studies should be carried out at said frequencies.

 

Comments:

It seems like you've conducted a detailed study on the effects of various retinal neurotransmitters on temporal resolution, particularly focusing on Critical Flicker Fusion Frequency (CFF) in mice. Here's a breakdown of your methods, results, and conclusions:

### Methods:
- **Experimental Setup:** Binocular physiologic electroretinogram on adult mice.
- **Groups:** Control group received PBS in the right eye. Experimental group received PBS in the left eye and PBS with different added molecules in the right eye.
- **Molecules Added:** APB, Glutamate, GABA, DNQX, Bicuculline, Glycine, HEPES.
- **Recording:** Initially recorded rod response followed by cone response.

### Results:
- **APB:** Suppressed rod-driven response but not cone-driven flicker response.
- **Other Agents:** Severely affected lower flickering frequency response amplitude, particularly at 3 Hz.
- **Threshold of CFF:** Lowered from 50 Hz to 40 Hz by APB, Glycine, and HEPES.
- **GABA:** Enhanced both rod-driven and cone-driven flicker response at 3 Hz. Glutamate and GABA/Glutamate enhanced only the rod-driven flicker response.

### Conclusions:
- **Visual Pathways:** Both ON and OFF visual pathways implicated in cone-driven response; only ON pathway relevant in rod-driven flicker response.
- **Role of Horizontal Cells:** Enhancement of flicker response observed in both rod-driven and cone-driven responses.
- **Sensitivity at Low Frequencies:** Pathophysiological studies should focus on low frequencies due to greater flicker sensitivity.

Your study highlights the differential effects of neurotransmitters on rod and cone-driven flicker responses and the involvement of specific pathways in these responses. The findings suggest potential implications for pathophysiological research focusing on low-frequency flicker responses.

Is there anything specific you're aiming to explore further or any particular aspect you'd like to discuss in more detail?

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