Vomeronasal amygdala

Kevetter G.A. and Winans S. (1981). Connections of the cortico-medial amygdala in the golden hamster Mesocricetus auratus, 1. Efferents of the vomeronasal amygdala . J Comp Neurol 197, 81-98. 

Mohedano-Moriano A, Pro-Sistiaga P, Ubeda-Banon I, Crespo C, Insausti R, Martinez-Marcos A (2007) Segregated pathways to the vomeronasal amygdala differential projections from the anterior and posterior divisions of the accessory olfactory bulb. Eur 1 Neurosci 25 2065-2080... 

Salazar I, Brennan PA (2001) Retrograde labelling of mitral/tufted cells in the mouse accessory olfactory bulb following local injections of the lipophilic tracer Dil into the vomeronasal amygdala. Brain Res 896 198-203... 

Fig. 2.19 Central pathways and nuclei, (a) Frog AOS Pl/Pm = lateral and medial pallium EP = post, olfactory eminence and nSm = medial Septal nucleus (from Kratskin, 1995). Reptiles and mammals-—afferent pathways from AOB to amygdala nuclei (Cortical C3 and Medial M), with tertiary connections to other central nuclei in hypothalamus (MPOA, VMH and PMN) (from Johnston, 2000). (b) Snake AOS Second-order projection of accessory fibres nAOT - nucleus of AOT AM = anterior amygdala and nSph = nucleus Sphericus. (c) Mammal AOS Projection sites of vomeronasal fibres in cortex and hypothalamus (from Johnston, 1998).

Herrick C. (1921). Connections of the vomeronasal organ, accessory olfactory bulb and amygdala in amphibia. J Comp Neurol 33, 213-280. 

Lanuza E. and Halpem M. (1997). Afferent and efferent connections of the nucleus sphericus in the snake Thamnophis sirtalis convergence of olfactory and vomeronasal information in the lateral cortex and the amygdala. J Comp Neurol 385, 627-640. 

Lehman M.N. and Winans S.S. (1982). Vomeronasal and olfactory pathways to the amygdala controlling male hamster sexual behavior — autoradiographic and behavioral analyses. Brain Res 240, 27-41. 

By contrast, the accessory olfactory system is thought to be involved in the detection of odors that influence a variety of reproductive and aggressive behaviors (Keverne 1999). Sensory neurons are located in the vomeronasal organ (VNO) and detect pheromones which gain access to the VNO by a pumping mechanism (Meredith and O Connell, 1979). VNO neurons send projections to the accessory olfactory bulb (AOB). Mitral cells of the AOB project in turn to the medial nucleus of the amygdala olfactory information is then dispatched to several hypothalamic regions such as the bed nucleus of the stria terminalis, the medial preoptic area and the ventromedial hypothalamus (Scalia and Winans 1975). 

Fig. 35.1 Simplified diagram of chemosensory circuit in amygdala. Vomeronasal input via accessory olfactory bulb (VNO/ AOB) is analyzed in anterior and posterior medial amygdala (MeA, MeP). MeP appears to be inhibited by intercalated nucleus (ICNc) for heterospecific and artificial stimuli. MOE/ MOB Main olfactory epithelium/Main olfactory bulb. ACN Anterior Cortical Nucleus. PC Piriform Cortex. BLA Basolateral amygdala. ICNr rostral part of medial intercalated nucleus. ICNc caudal part of ICN. MPOA Medial Preoptic Area. VMH Ventro-medial hypothalamus...

Nolte, C, and Meredith, M. (2005). mGluR2 activation of medial amygdala input impairs vomeronasally-mediated behavior. Physiol. Behav. 86, 314-323. 

Fig. 3 Vomeronasal system. Schematic representation of a rodent nasal cavity and brain (lateral view). Accessory olfactory bulb (AOB) mitral cells project to vomeronasal and extended amygdala. Inset The VNO is a bilateral tubular structure located at the base of the nasal septum. VSNs that express the same V1R or V2R converge on a small number of glomeruli in the AOB. Sensory neurons located in the apical layer of the epithelium project to the anterior part of the AOB, whereas those present in the basal layer project to the posterior part. MOE main olfactory epithelium, MOB main olfactory bulb, BSTMPM posteromedial bed nucleus of the stria terminalis, MEA medial amygdaloid nucleus, BACfF bed nucleus of the accessory olfactory tract, PMCO posteromedial cortical amygdaloid area...

Newman SW (1999) The medial extended amygdala in male reproductive behavior. A node in the mammalian social behavior network. Ann N Y Acad Sci 877 242-257 Norlin EM, Gussing F, Berghard A (2003) Vomeronasal phenotype and behavioral alterations in G mutant mice. Curr Biol 13 1214-1219... 

In macrosomatic animals, the AOB is believed to be involved in processing pheromones that are initially transduced by vomeronasal neurons, which project to the AOB. The AOB projects to the anteromedial (MeAa) and posterior cortical (CoAp) nuclei of the amygdala, the bed nucleus of the stria terminalis and the bed nucleus of the accessory olfactory tract (De Olmos et al. 1978 Scalia and Winans, 1975 Shipley and Adamek,... 

Figure 2. Schematic diagram of the nasal cavities and forebrain of a salamander, illustrating the central projections of the olfactory and vomeronasal systems in dorsal view. Anterior is toward the top of the figure, and only ipsilateral projections are shown. The medial (A) and lateral (B) olfactory tracts arise from the olfactory bulb. (C) The extra-bulbar ol ctory pathway bypasses the olfactory bulb and projects directly to the anterior preoptic area. (D) The accessory olfactory bulb, which receives input from the vomeronasal organ, projects to the lateral amygdala (la). Other abbreviations apoa = anterior preoptic area dp = dorsal pallium Ip = lateral pallium mp = medial pallium ma = medial amygdala s = septum sir = striatum. Based on descriptions in Hetrick, 1927,1933,1948 Kokoros and Northcutt, 1977 and Schmidt and Roth, 1990.

Studies of c-fos expression in the accessory olfactory system have been performed almost exclusively in the context of sexual behavior of animals (Fiber, Adames Swann, 1993 Schellinck, Smyth, Brown Wilkinson, 1993 Baum, Brown, Kica, Rubin, Johnson Papaioannou, 1994 Femandez-Fewell and Meredith, 1994 Rajendren and Moss, 1994 Bressler and Baum, 1996). Many studies show that c-fos is expressed in the vomeronasal projection circuit (i.e. the anterior olfactory bulb, the medial amygdala, the posterior medial bed nucleus of the stria terminalis, or the medial preoptic area) after mating behavior. Importantly, there have been no reports of specific c-fos expression in the VNO. 

---