Monoaminergic innervation of the macaque extended amygdala

The extended amygdala is a group of structures including the central and me dial amygdaloid nuclei, bed nucleus of the stria terminalis, and sublenticu lar substantia innominata. This group of structures is thought to be import ant in a variety of psychiatric disorders. many of which are linked in one way or another to monoamines and their transporters. However, not much is k nown about the distribution of these molecules in the primate extended amyg dala. Thus, we mapped the distribution of fibers immunoreactive for tyrosin e hydroxylase, dopamine beta -hydroxylase, serotonin, dopamine transporter, and serotonin transporter in the brains of macaque monkeys. Tyrosine hydroxylase, serotonin, and serotonin transporter-immumoreactive f ibers were found in highest concentrations in the lateral division of the c entral nucleus and lateral dorsal part of the bed nucleus of the stria term inalis. Dopamine beta -hydroxylase-immunoreactive fibers were found in the highest concentration in the lateral ventral bed nucleus of the stria termi nalis. Dopamine transporter-immunoreactive fibers were found in the highest concentrations in the lateral juxtacapsular and lateral dorsal capsular su bnuclei of the bed nucleus and lateral capsular subnucleus of the central a mygdaloid nucleus, though in much lower amounts than was present in the str iatum. These results suggest prominent roles for these transmitters, particularly in the lateral dorsal bed nucleus and lateral part of the central nucleus. The relative absence of dopamine transporter in the extended amygdala sugge sts that this transmitter acts more through volume transmission while serot onin, which is generally accompanied by proportionate amounts of transporte r. may act more like a classical neurotransmitter. In addition. the finding of heavy concentrations of dopamine- and serotonin-immunoreactive fibers i n the lateral central nucleus and lateral dorsal bed nucleus lends further support to the idea of these areas as parallels in some respects to the str iatum. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserve d.