Nucleus of the accessory olfactory tract

Collado P. and Segovia S. (1992). Female s DHT controls sex differences in the rat bed nucleus of the accessory olfactory tract. Neuroreport 3, 327-329. 

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...

BAC bed nucleus of the anterior commissure 21, 81,102-103 BAOT bed nucleus of the accessory olfactory tract 26-29, 84,90-91 Bar Barrington s nucleus 56-60,99-100 bas basilar artery 45-66, 79... 

Abbreviations ACo = anterior cortical amygdaloid nucleus AOB = accessory olfactory bulb Me = medial amygdaloid nucleus AON = anterior olfactory nucleus (m = medial division) PCo = posterior cortical amygdaloid nucleus BST = bed nucleus of the stria terminalis DHR = dorsal hippocampal rudiment DPC = dorsal peduncular cortex DR = dorsal raphe nucleus Ent = entorhinal cortex LC = locus coeruleus LPO = lateral preoptic area MOB = main olfactory bulb MnR = median raphe BAOT = nucleus of the accessory olfactory tract NLOT = nucleus of the lateral olfactory tract DB = nucleus of the diagonal band PeCo = periamygdaloid cortex Pir = piriform cortex Tu = olfactory tubercle TT = taenia tecta... 

The AOB has direct projections to the amygdala, specifically to the medial and posterior cortical nuclei, the bed nucleus of the stria terminalis and the nucleus of the accessory olfactory tract. These pathways may be involved in the processing of pheromonal information. Neurons in the AOB targets express gonadal steroid receptors and thus may be modulated directly by circulating hormones. The efferent connections of the accessory olfactory system are summarized in Fig. 22. 

There are major differences between centrifugal inputs to MOB and AOB. First, centrifugal inputs to AOB arise from far fewer brain regions than inputs to MOB. The major afferents to AOB are from the bed nucleus of the stria terminalis, the nucleus of the accessory olfactory tract, the medial amygdala nucleus and the posteromedial cortical amygdala nucleus (De Olmos et al. 1978 Shipley and Adamek, 1984). A restricted part of the medial division of AON sends a dense projection to the granule cell layer of AOB (Rizvi et al. 1992), but all other divisions of AON lack connections with AOB. 

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,... 

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