Monoamine-containing neurons in the optic ganglia of crustaceans and insects

With the fluorescence method of Falck and Hillarp, the presence and localization of monoaminergic neurons in the optic ganglia of several crustaceans and insects have been investigated. It was found that in both classes the monoaminergic terminals, when present, appeared (especially in the medullae externa and interna of the crustaceans and the medulla of the insects) in strata specific for each species. So far, the only monoamine (visualized by this technique) present in the crustacean optic ganglia is dopamine, whereas in the Insecta, the catecholamines dopamine and noradrenaline, and the indolamine, 5-hydroxytryptamine, are found in the optic lobe. But in the Insecta, different species show different content of these amines.