Histamine in retina, optic nerve, choroid and brain of albino and pigmented rabbits

Retina, optic nerve and various brain structures of both albino and pigmented rabbits contained histamine in the range of 40-400 ng/g tissue; choroid of both animal strains was characterized by several times higher amine content, i.e. 1.2-5.5 micrograms/g tissue. Among the studied structures the brain tissue was the only one able to synthesize substantially histamine from 1-histidine. Histological analysis of the ocular structures revealed the presence of mast cells only in the choroid of both albino and pigmented rabbits. Incubation of either the retina or optic nerve or choroid with compound 48/80 produced release of histamine only from the choroid.