Monoamino-oxidase activity in rat pineal gland. Histochemical studies

Monoamine-oxidase (MAO) activity was detected in rat pineal gland with dopamine, 5-hydroxytryptamine (5-HT), norepinephrine and tryptamine as substrates, and nitroblue tetrazolium salt as electron acceptor. Pinealocytes stained deeply when 5-HT was the substrate. Dopamine and tryptamine substrates gave similar patterns, with moderate activity in the pinealocytes. Norepinephrine reactivity was detected in the nerve-endings.