Lm. Coolen et Ri. Wood, BIDIRECTIONAL CONNECTIONS OF THE MEDIAL AMYGDALOID NUCLEUS IN THE SYRIAN-HAMSTER BRAIN - SIMULTANEOUS ANTEROGRADE AND RETROGRADE TRACT TRACING, Journal of comparative neurology, 399(2), 1998, pp. 189-209
In the male Syrian hamster, mating is dependent on chemosensory and ho
rmonal stimuli, and interruption of either input prevents copulation.
The medial amygdaloid nucleus (Me) is a key nodal point in the neural
circuitry controlling male sexual behavior because it relays both odor
and steroid cues. Me is comprised of two major subdivisions, anterior
(MeA) and posterior (MeP), which have distinct, although overlapping
efferent projections. The present study investigated the afferents and
efferents of MeA and MeP by using combined anterograde and retrograde
tract tracing. Phaseolus vulgaris-leucoagglutinin and cholera toxin B
were injected by iontophoresis through a single glass micropipette an
d detected by immunohistochemistry. MeA has widespread connections wit
h olfactory structures, whereas MeP is heavily interconnected with ste
roid-responsive brain regions. The efferent projections of MeA and MeP
were similar to those reported previously for the rat and hamster. In
particular, MeP projects to the posteromedial subdivision of the bed
nucleus of the stria terminalis (BNST) and to the medial preoptic nucl
eus, whereas MeA projects to adjacent subnuclei in BNST and the preopt
ic area. MeA and MeP also have distinct patterns of afferent input. Fu
rthermore, the combination of anterograde and retrograde tract tracers
shows that MeA and MeP are each bidirectionally connected with each o
ther and with limbic nuclei. These results demonstrate that subnuclei
of Me are interconnected with limbic structures in hamster brain. Thes
e connections may contribute to chemosensory and hormonal integration
to control male sexual behavior. J. Comp. Neurol. 399:189-209, 1998. (
C) 1998 Wiley-Liss, Inc.