Histamine in the retina: recent progress and perspectives.

This article presents some new findings, and shortly surveys recently published data, on histamine (HA) in the retina of several vertebrates (carp, hen, rabbit, rat, guinea pig, cow, man). Analysis of various parameters (HA level, activity of histidine decarboxylase and HA-methyltransferase, release and uptake of HA, 3H-mepyramine binding, effect of HA on cAMP accumulation, diurnal variations) in vertebrate retina and brain shows that histaminergic systems in these sites are comparable, although some species-dependent differences have been observed. Interestingly, exposure of dark-adapted rabbits to light affects several histaminergic parameters selectively, i.e. in the retina and not in the brain. The reviewed data suggest that in retinas of at least some vertebrates HA may be a physiologically important amine.