Striatal and central extended amygdala parts of the interstitial nucleus of the posterior limb of the anterior commissure: Evidence from tract-tracing techniques in the rat

The interstitial nucleus of the posterior limb of the anterior commissure (IPAC) lies at the junction of the striatopallidal system and the lateral bed nucleus of the stria terminalis‐central amygdaloid nucleus continuum (i.e., the central extended amygdala; EAc). Its efferent connections were inves...

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Bibliographic Details
Published in:Journal of comparative neurology (1911) 2001-10, Vol.439 (1), p.104-126
Main Authors: Shammah-Lagnado, Sara J., Alheid, George F., Heimer, Lennart
Format: Article
Language:English
Subjects:
Amygdala - physiology
Animals
basal forebrain
Brain Mapping
central amygdaloid nucleus
Cholera Toxin
Corpus Striatum - physiology
Efferent Pathways - physiology
extended amygdala
Female
Fluorescent Dyes
fundus striati
interstitial nucleus
midline thalamus
Phytohemagglutinins
Rats - physiology
Rats, Wistar
Stilbamidines
ventral striatum
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Summary:The interstitial nucleus of the posterior limb of the anterior commissure (IPAC) lies at the junction of the striatopallidal system and the lateral bed nucleus of the stria terminalis‐central amygdaloid nucleus continuum (i.e., the central extended amygdala; EAc). Its efferent connections were investigated in the rat with anterograde (Phaseolus vulgaris leucoagglutinin) and retrograde (Fluoro‐Gold and cholera toxin B subunit) tracers and compared with those of the central amygdaloid nucleus. Our anterograde tracing experiments reveal that the projections of the medial IPAC largely reciprocate its afferent connections (Shammah‐Lagnado et al. [1999] Neuroscience 94:1097–1123) and are very similar to those of the medial part of the central amygdaloid nucleus. The lateral IPAC, on the other hand, innervates the pallidal complex, substantia nigra and retrorubral field. Local connections are found within medial IPAC and within lateral IPAC, but the two divisions are not interconnected. Our retrograde tracing experiments confirm that IPAC projections to EAc components, parabrachial area, and nucleus of the solitary tract originate chiefly from the medial division, whereas both medial and lateral divisions innervate the retrorubral field. Moreover, in sections processed for choline acetyltransferase, the strong projections from caudal IPACm to the posterior basolateral amygdaloid nucleus and the amygdalopiriform transition area were found to arise chiefly from cholinergic cells. Overall, our results suggest that the medial IPAC is intimately related to the EAc, whereas the lateral IPAC represents a striatal territory. J. Comp. Neurol. 439:104–126, 2001. © 2001 Wiley‐Liss, Inc.
ISSN:0021-9967
1096-9861
DOI:10.1002/cne.1999