Abstract
The medial amygdaloid nucleus (Me) is a key structure in the control of sociosexual behavior in mice. It receives direct projections from the main and accessory olfactory bulbs (AOB), as well as an important hormonal input. To better understand its behavioral role, in this work we investigate the structures receiving information from the Me, by analysing the efferent projections from its anterior (MeA), posterodorsal (MePD) and posteroventral (MePV) subdivisions, using anterograde neuronal tracing with biotinylated and tetrametylrhodamine-conjugated dextranamines. The Me is strongly interconnected with the rest of the chemosensory amygdala, but shows only moderate projections to the central nucleus and light projections to the associative nuclei of the basolateral amygdaloid complex. In addition, the MeA originates a strong feedback projection to the deep mitral cell layer of the AOB, whereas the MePV projects to its granule cell layer. The Me (especially the MeA) has also moderate projections to different olfactory structures, including the piriform cortex (Pir). The densest outputs of the Me target the bed nucleus of the stria terminalis (BST) and the hypothalamus. The MeA and MePV project to key structures of the circuit involved in the defensive response against predators (medial posterointermediate BST, anterior hypothalamic area, dorsomedial aspect of the ventromedial hypothalamic nucleus), although less dense projections also innervate reproductive-related nuclei. In contrast, the MePD projects mainly to structures that control reproductive behaviors [medial posteromedial BST, medial preoptic nucleus, and ventrolateral aspect of the ventromedial hypothalamic nucleus], although less dense projections to defensive-related nuclei also exist. These results confirm and extend previous results in other rodents and suggest that the medial amygdala is anatomically and functionally compartmentalized.
Highlights
The main and accessory olfactory systems provide key sensory inputs to the network of neural structures controlling sociosexual behaviors in rodents (Swann et al, 2009)
For the description of the distribution of anterograde labeling resulting from the different injections in the medial amygdaloid nucleus (Me), we follow the nomenclature of the atlas of the mouse brain by Paxinos and Franklin (2004)
REMARKS The efferent projections of the three subdivisions of the Me revealed by our results show the following main characteristics (Figure 9): 1. The pattern of efferent projections of the medial amygdaloid subnuclei found in female mice is very similar to that reported in male rats and male hamsters
Summary
The main and accessory olfactory systems provide key sensory inputs to the network of neural structures controlling sociosexual behaviors in rodents (Swann et al, 2009) This network is composed of a number of interconnected nuclei rich in neurons expressing receptors for sexual steroids, including the medial amygdaloid nucleus (Me), the posterior bed nucleus of the stria terminalis (BST), the lateral ventral septum, and the medial preoptic area (MPA) (Newman, 1999). Among these structures, only the Me receives convergent projections from the main and accessory olfactory bulbs (AOB) (Scalia and Winans, 1975; Pro-Sistiaga et al, 2007; Kang et al, 2009, 2011). The MeA contains a population of Lhx5-expressing neurons originated in the hypothalamic supraoptoparaventricular domain (Abellán et al, 2010) and
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
