Dopamine-beta-hydroxylase and tyrosine hydroxylase immunoreactive neurons in the human brainstem

Immunohistochemistry of dopamine-beta-hydroxylase in the human hind brain indicates that neuronal cell bodies containing the antigen form prominent populations in the nucleus tractus solitarius and nearby medial and dorsal edge of the medial vestibular nucleus. They are frequent in and around the periphery of the dorsal motor nucleus of the vagus and in an oblique band extending from that region to the ventrolateral aspect of the reticular formation, where they are most numerous at the mid medullary levels. Dopamine-beta-hydroxylase immunoreactive neurons are also closely packed in the nuclei coeruleus and subcoeruleus. Concomitant immunohistochemistry for tyrosine hydroxylase demonstrates small numbers of neuronal cell bodies that are reactive only for this antigen, and which do not contain detectable dopamine-beta-hydroxylase. Such neurons are present in the nucleus tractus solitarius, the pontine lateral parabrachial nucleus and within the core of the rostral pontine reticular formation. Some medullary and pontine axon bundles similarly stain for tyrosine hydroxylase but not for dopamine-beta-hydroxylase. These differential staining patterns suggest, among other possibilities, that in humans some neurons of the caudal brainstem are dopamine (if they contain the second step catecholamine synthesizing enzyme, aromatic L-aminoacid decarboxylase) rather than noradrenaline or adrenaline containing catecholamine neurotransmitters.