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Updated: Aug 9, 2026

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Immunohistochemical and Calcium Imaging Methods in Wholemount Rat Retina
Published on: October 13, 2014
Histaminergic mechanisms in the vertebrate visual system
Summary
Histamine (HI) plays a role in the vertebrate visual system. This study maps HI distribution and function in various species, revealing its potential involvement in visual processes.
Area of Science:
- Neuroscience
- Ophthalmology
- Biochemistry
Background:
- Histamine (HI) is a neurotransmitter with known roles in the central nervous system.
- Its presence and function in the vertebrate visual system are not fully elucidated.
Purpose of the Study:
- To investigate the distribution, localization, synthesis, metabolism, and functional roles of histamine in the vertebrate visual system.
- To explore the effects of light stimulation and diurnal variations on histamine levels and related enzyme activities.
Main Methods:
- Histological examination of HI distribution and localization.
- Biochemical assays for HI synthesis, uptake, and metabolism.
- Radioligand binding studies (3H-mepyramine) and cAMP assays.
- Measurement of enzyme activities (histidine decarboxylase, histamine-methyltransferase).
- Analysis of HI content under different light conditions and diurnal cycles.
Main Results:
- Histamine is found in the retina, optic nerve, choroid, and brain of various vertebrate species, including humans.
- Evidence suggests histamine is involved in a cAMP-generating system in the rabbit eye.
- Light stimulation affects histamine levels in the rabbit retina, optic nerve, and brain.
- Diurnal variations in enzyme activities related to histamine metabolism were observed in rabbit ocular and brain structures.
Conclusions:
- Histamine is a significant molecule within the vertebrate visual system.
- Its distribution and modulation by light and diurnal cycles suggest a functional role in visual processing and regulation.
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