Olfactory communication secretions

Many of the proteins in scent marks are members of the lipocalin superfamily, characterised by their distinctive barrel shaped structure and central ligand binding pocket. Given the well established role of volatile compounds in olfactory communication (Buck and Axel, 1991), the function of semiochemical proteins may be to modulate scent signals by interaction with volatile components. Thus, a further step in characterising a novel scent secretion protein may be to identify and characterise any associated ligands. 

The major urinary proteins (MUPs) are secreted abundantly into mouse urine as a normal condition. MUPs are thought to be involved in olfactory communication as their distinctive barrel shape allows them to bind two semiochemical molecules. Production of MUPs results from simultaneous expression of a number of closely related MUP genes the mature proteins therefore have heterogeneous amino acid sequences. Whilst this heterogeneity has been characterised in inbred mice, little is known about the heterogeneity of MUPs in wild mice. No function has ever been ascribed to MUP heterogeneity. 

The isolated boar ketones, 5a-androst-16-en-3a-ol (androstenol) and androst-16-en-3-one (androstenone) secreted by the sub-maxillary gland, have a direct effect on the sexual receptivity of the sow and are used commercially to assist in artificial insemination (14). The fact that estrus can be determined in the sow by her response to these compounds suggests that there is a heightened acuity for these compounds at the time of ovulation. This is similar to the increase in olfactory acuity for certain compounds noted in human females prior to ovulation (15). A somewhat unique but analogous situation is the elephant temporal gland which is an apocrine gland that is active under stress and possesses an elephanty odor (16). Table III summarizes some of the mammalian communication systems that have been studied and the chemicals which have been found to have behavioral effects. 

Karlson and Liischer (1959) proposed the term pheromone to describe substances which are excreted to the outside by an individual and received by a second individual of the same species in which they release a specific reaction, for example a definite behavior or a developmental process. Lacking identified pheromonal compounds, they provide a description that is understandably vague but strongly implies that pheromones are potent, instinctually recognized, and specific in their actions. However, Karlson and Liischer (1959) also state that strict species-specific activity is not required, that pheromones may be either oral or olfactory, that unlike hormones, the substance is not secreted into the blood but outside the body, and that pheromones function in communication between conspecifics. Although they do not define communication , it seems clear that they are using the term simply to describe the conveyance of information from one organism to... 

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