Olfactory bulb connections with basal rhinencephalon in the ferret: An evoked potential and neuroanatomical study

Abstract

The lateral olfactory tract (LOT) of the ferret has been shown to project to most of the pyriform lobe, as in the cat. Only a small medio-posterior region of the pyriform cortex (the angular cortex), which has a distinctly different appearance in Nissl stained sections, proves to be devoid of olfactory connections. Despite the fact that sub-areas can be recognized within olfactory cortex, there is an underlying constancy in design throughout. Latency measurements indicate that fine collateral branches of theLOT reach the posterior olfactory cortex, whereas mainly larger diameter (faster conducting) fibres comprise the contribution to anterior olfactory cortex. Thus in the present context it is sufficient to recognise just an anterior and posterior subdivisionof olfactory cortex, contingent on the above criterion and correlated with cytoarchitectural features, chiefly variations in cortical layers II and III of the regions concerned. Pyriform cortex directly in receipt of LOT fibres, and associated deeper cortical zones, generated potentials in the olfactory bulbs which can only be attributed to centrifugal input, thus further substantiating an olfactory role for this cortex. In addition, non-cortical regions in receipt of LOT fibres, namely the anterior olfactory nucleus, olfactory tubercle, cortical amygdaloid nucleus and nucleus of the lateral olfactory tract, also contribute centrifugal input to the bulbs. All these regions are thereby capable of providing a rather direct feedback on olfactory bulb activity. The exact pathways concerned have yet to be determined.

The Ferret's vomeronasal organ and accessory olfactory bulb: Effect of hormone manipulation in adult males and females

“…These workers found no difference in VNO sensory epithelium volume in gonadally intact male ferrets killed during the reproductive (spring) and non-reproductive (fall) seasons. Furthermore, in preliminary studies (Chang et al, 2001;Wersinger and Baum, 1997b;Kelliher et al, 1998) we reported the presence of an AOB in a different location from that previously described for ferrets (Dennis and Kerr, 1969;Lockard, 1985). In our experiments we showed that either mating (Wersinger and Baum, 1997b), exposure to soiled bedding from male or female ferrets (Kelliher et al, 1998), or exposure to maternal odors (Chang et al, 2001) induced Fos-immunoreactivity (Fos-IR; an index of neuronal activation) in granule cells of the main olfactory bulb (MOB) but not in the AOB.…”

“…Both of these shortcomings are evident in previous studies that specified the location of an AOB in the carnivore subfamily, Mustelidae. Thus, an AOB was reportedly either absent (weasel, polecat, and marten: Jawlowski, 1956) or poorly delineated while occupying the entire dorsal-caudal portion of the olfactory bulb (weasel: Crosby and Humphrey 1939;mink: Jeserich, 1945; ferret: Dennis and Kerr, 1969;Lockard, 1985). The suggestion that the AOB of these Mustelid species encompasses the entire dorsal-caudal portion of the olfactory bulb was likely based on expectations derived from rodent studies and on the exclusive use of hematoxylin-stained coronal sections to assess AOB structure.…”

“…We studied the possible activational effects of TP treatment on the VNO-AOB morphology because our previous study (Kelliher et al, 1998) showed that this steroid dramatically enhanced neuronal Fos responses to estrous odors in several forebrain regions of both male and female ferrets. Since our recent characterization (e.g., Wersinger and Baum, 1997a,b;Kelliher et al, 1998) of the location of the ferret's AOB does not correspond with that of earlier studies (Dennis and Kerr, 1969;Lockard, 1985), we used several histochemical markers to confirm the location and size of this structure in the adult ferret. These included staining for soybean agglutinin (SBA), which binds specifically to glycoconjugates located on the vomeronasal nerve (Key and Giorgi, 1986).…”

Basal telencephalic regions connected with the olfactory bulb in a Madagascan hedgehog tenrec

“…This observation even applies to the nucleus of the lateral olfactory tract, which may be the most unequivocal amygdalar region among macrosmatic mammals (Stephan, 1975). Reportedly, the nucleus of the lateral olfactory tract not only gives rise to the most prominent amygdalar projection to the OfB (Dennis and Kerr, 1975;De Olmos et al, 1978;Luskin and Price, 1983;Carson, 1984;Shipley and Adamek, 1984;De Carlos et al, 1989;Jansen et al, 1998) but also receives a substantial bulbar input (Price, 1973;Broadwell, 1975;Davis et al, 1978;Turner et al, 1978;De Olmos and Spada, 1980;Shammah-Lagnado and Negrao, 1981;Shipley et al, 1996;Jansen et al, 1998). In the tenrec, there may also be a bulbar projection to the lateral OfT; however, its intensity is much lower than that to the remaining portions of the olfactory amygdala.…”

Mucosal transmission and pathogenesis of chronic wasting disease in ferrets

“…exposure) in the current study had relatively large amounts of PrP CWD in the olfactory epithelium and olfactory bulb, respectively. Although we investigated the lateral olfactory tract projection(s) described in ferrets (Dennis & Kerr, 1975) in order to show distribution patterns reflective of n.ph. versus i.g.…”