Mammalian olfactory signals

Mackintosh, J.H., 1985, The bioassay of mammalian olfactory signals. Mammal Rev. 15 57-70. 

Berghard A., Buck L. and Liman E. (1996). Evidence for distinct signaling mechanisms in two mammalian olfactory sense organs. Proc Natl Acad Sci 93, 2365-2369. 

At first glance, labeled-line coding of olfactory signals may seem in contrast to the ensemble or across-fiber code (Shepherd, 1985) where complex mixtures of odorants or even individual odorant components are perceived as patterns of activity across an ensemble of neurons and AL glomeruli. However, recent experiments examining odor coding of individual ORNs in Drosophila and mammalian olfactory systems demonstrate that individual ORNs are capable of a wide spectrum of responses. In the fly, a particular odor can excite one neuron while inhibiting another, and a particular neuron can be excited by one odor and... 

Mammalian pheromones released into their environment can readily reach their target tissue, either the main olfactory epithelium (MOE) or the VNO. Both target tissues are lined with an olfactory neuroepithelium that contains membrane-bound receptor proteins, which comprise the largest known family of G-protein-coupled [262] receptors in mammals. The number of mammalian olfactory receptors [263-265] found has been astonishing, but not unreasonable. The MOE and VNO have some common features, but also significant difierences in neuron types, primary structures of receptor proteins and signal transduction [266]. 

Generally we find much similarity in the structure of the olfactory systems of marsupials and placentals. Therefore, marsupials should be considered excellent models for certain types of behavioural research and must be included in any general model of mammalian behavior. In this context it would be very valuable to further investigate the use of olfactory communication in marsupials which could give us additional insights into the function of olfactory signals in all mammals. 

Olfactory Marker Protein ORNs express high levels of olfactory marker protein (OMP), which is unique in the olfactory system to ORNs (Margolis, 1972 Keller and Margolis, 1975). OMP is found in a number of mammalian species and it appears to be expressed in all mature ORNs. Studies in mice containing a null mutation for OMP suggest that this protein may play a role in ORN adaptation to odors (Ivic et al., 2000), signal amplification, and transduction (Youngentob et al., 2004). 

CNG channels (cyclic nucleotide-gated ion channels) are activated by the binding of cyclic GMP. They mediate sensory signal transduction in photoreceptors and olfactory cells. Six mammalian CNG channel genes are known and some human visual disorders are caused by mutations in retinal rod or cone CNG genes. ... 

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