The efferent connections of the nucleus of the lateral olfactory tract (LOT) were examined in the rat with the Phaseolus vulgaris leucoagglutinin (PHA-L) technique. Our observations reveal that layers II and III of LOT have largely segregated outputs. Layer II projects chiefly ipsilaterally to the olfactory bulb and anterior olfactory nucleus, bilaterally to the anterior piriform cortex, dwarf cell cap regions of the olfactory tubercle and lateral shell of the accumbens, and contralaterally to the lateral part of the interstitial nucleus of the posterior limb of the anterior commissure. Layer III sends strong bilateral projections to the rostral basolateral amygdaloid complex, which are topographically organized, and provides bilateral inputs to the core of the accumbens, caudate-putamen, and agranular insular cortex (dorsal and posterior divisions). Layer II projects also to itself and to layers I and II of the contralateral LOT, whereas layer III projects to itself, to ipsilateral layer II, and to contralateral layer III of LOT. In double retrograde labeling experiments using Fluorogold and cholera toxin subunit b tracers, LOT neurons from layers II and III were found to provide collateral projections to homonymous structures on both sides of the brain. Unlike other parts of the olfactory amygdala, LOT neither projects directly to the extended amygdala nor to the hypothalamus. Thus, LOT seemingly influences nonpheromonal olfactory-guided behaviors, especially feeding, by acting on the olfactory bulb and on ventral striatal and basolateral amygdaloid districts that are tightly linked to lateral prefrontal cortical operations.

No abstract

The amygdalopiriform transition area (APir) is often considered part of the lateral entorhinal cortex (Entl). However, in contrast to Entl, APir densely innervates the central extended amygdala (EAc) and does not project to the dentate gyrus. In order to gain a more comprehensive understanding of these territories, the afferent connections of APir were examined in the rat with retrograde (cholera toxin B subunit or FluoroGold) and anterograde tracers (Phaseolus vulgaris leucoagglutinin) and compared to those of the neighboring Entl. The results suggest that APir and Entl are interconnected and receive topographically organized hippocampal projections. Both are targeted by the olfactory bulb, the piriform, posterior agranular insular and perirhinal cortices, the ventral tegmental area, dorsal raphe nucleus, and locus coeruleus. Most importantly, the data reveal that APir and Entl also have specific inputs and should be viewed as separate anatomical entities. The APir receives robust projections from structures affiliated with the EAc, including the anterior basomedial and posterior basolateral amygdaloid nuclei, the gustatory thalamic region, parasubthalamic nucleus, and parabrachial area. The Entl is a major recipient for amygdaloid projections from the medial part of the lateral nucleus and the caudomedial part of the basolateral nucleus. Moreover, the medial septum, subicular complex, nucleus reuniens, supramammillary region, and nucleus incertus, which are associated with the hippocampal system, preferentially innervate the Entl. These data underscore that APir processes olfactory and gustatory information and is tightly linked to EAc operations, suggesting that it may play a role in reward mechanisms, particularly in hedonic aspects of feeding.

E aos que estiveram presentes no agradável convívio da universidade e, mesmo distantes, participaram deste processo. 1.0. INTRODUÇÃO A área de transição amígdalo-piriforme (APir) está situada na encruzilhada dos córtices piriforme, periamigdalóide e entorrinal, ocupando o distrito localizado no fundo e no lábio lateral da fissura amigdalóide (Haug, 1976; Paxinos e Watson, 1986; Alheid e cols., 1995). Sua porção rostral é estreita e limitada lateralmente pelo córtex piriforme, medialmente pelo núcleo amigdalóide cortical póstero-lateral e dorsalmente pelo núcleo amigdalóide basolateral posterior. Acompanhando o eixo ântero-posterior da APir, identificamos uma porção intermédia que ocupa um território interposto entre o córtex entorrinal (subdivisão dorsolateral), o núcleo amigdalóide cortical póstero-medial e a área amígdalo-hipocampal. O pólo mais caudal desta área de transição é limitado, e posteriormente substituído, pelas subdivisões ventromedial e ventrolateral do córtex entorrinal lateral (Krettek e Price, 1977). Do ponto de vista citoarquitetônico, a APir diferencia-se das estruturas vizinhas pela grande espessura de sua camada molecular e pela ausência de um padrão laminar bem definido (Fig. 1). As células do estrato profundo (lâmina III) são maiores do que aquelas observadas no estrato superficial (lâmina II). Em sua porção caudo-lateral as células do estrato superficial formam tipicamente pequenos agregados celulares. A APir não apresenta portanto nenhuma semelhança citoarquitetônica com os córtices piriforme e entorrrinal. Existem diferentes nomenclaturas para designar esta área de transição no rato. Assim, a APir corresponde às áreas e2 e e3 de Popoff e Popoff (1929); à área de transição de Haug (1976); ao pólo mais rostral da FIGURA 1 FIGURA 1. Fotomicrografias em campo claro de cortes transversos apresentados em sequência rostro-caudal, ilustrando a citoarquitetura da APir (A e B) e do córtex entorrinal lateral (C).