Catecholamine content of pigmented and nonpigmented tissues of the rabbit

Norepinephrine and dopamine content of various tissues from albine and nonalbino (black fur) rabbits were chemically determined. Although norepinephrine content of the nonpigmented iris (7.93 μg/g) and the pigmented iris (6.8 μg/g) did not differ significantly, the latter type contained very high amounts of dopamine (6.5 μg/g). As compared to that from the albino animal, the retina from nonalbino animals also contained slightly higher levels of dopamine. Thus, in addition to previously proposed neurotransmitter role of dopamine in the retina, it may also serve as precursor for the biosynthesis of melanin in the pigmented tissues.