Immunohistochemical analysis of monoaminergic neurons in the brain of the common marmoset, Callithrix jacchus

The distribution pattern of monoaminergic neurons in the common marmoset (Callithrix jacchus) was determined on the basis of comparative morphology using immunohistochemical methods with specific laboratory-made antibodies to tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), dopamine-beta-hydroxylase, phenylethanolamine-N-methyltransferase and serotonin (5-HT). Dopaminergic (DA) neurons (A(16)-A(8) groups), noradrenergic neurons (A(7)-A(1) groups), and adrenergic neurons (C-1 and C-2 groups) were found. Serotonergic neurons were first found in the rostral part of the nucleus interpedunculalis where they were mainly distributed in the raphe nuclei (B-9-B-1 groups). However, no neurons of the B-4 group were found, contrasting with previous reports on rats. Characteristic findings on the distribution of monoaminergic neurons in the brain of the common marmoset were as follows: DA neurons other than those included in A groups were observed in the basal magnocellular nucleus; TH-only-immunoreactive (Ir) neurons and AADC-only-Ir neurons were occasionally found intermingled with DA neurons in the substantia nigra; and TH-Ir neurons coexisting with 5-HT-Ir neurons were found in the rostralmost area of the dorsal raphe nucleus. These results clearly show that patterns of monoaminergic neuron distribution in the brain of the common marmoset are unique and differ from those observed in rodents.