Pheromone, boar

Krzymowski T., Grzegorzewski W., Stefanczyk-Krzymowska S., Skipor J., et al. (1999). Humoral pathway for transfer of the boar pheromone androstenol, from the nasal mucosa to the brain and hypophysis of gilts. Theriogenol 52, 1225-1240. 

Pearce G.P. and Patterson A.M. (1992). Physical contact with the boar is required for maximum stimulation of puberty in the gilt because it allows transfer of boar pheromones and not because it induces cortisol release. Anim Reprod Sci 27, 209-224. 

In some mammals, the sexes differ in their odor thresholds. The sow detects the boar pheromone androstenone (5o -androsten-16-en-3-one) easily at 3.67 x 10 mol/l, while this concentration is near or below the threshold for boars. Boars initially could not detect the odor at all but became more sensitive after repeated exposure (Dorries etal, 1991). 

The well-known boar pheromone was not only one of the first mammalian pheromones identified, but also the first one applied commercially. The saliva from the submaxillaiy gland contains two steroids. These are 5a-androst-16-en-3-one and So -androst-lS-en-So -ol (Fig. 7.8). They are emitted during head-to-head contact in courtship. Both individually stimulate the sow to assume the mating stance, but a mixture of the two is not more active than either compound (Melrose etal., 1971). This may be a case of adaptive redundancy. 

Boar pheromones a model for the integration of endocrinology and exocrinol-o. Journal of Endocrinology 123 (Suppl.), 16. 

Claus, R. and Hoppen, H. O. (1979). The boar pheromone identified in vegetables. Experi-entia 35,1674-1675. 

At the level of chemical compounds, one compound may substitute for another, and the activity still remains the same. Different numbers and types of compounds in a single secretion may have the same effect. The puberty delay pheromone in female mice and the castoreum of beaver are examples. In the mouse, of six adrenal-dependent compounds, two acetates are active together, one pyrazine by itself, and all three together with no increase in activity (Novotny et al.). In beaver castoreum, a mixture of 12 neutrals (monoterpenes) released the same activity as 14 phenolics (Schulte et al. 1994). A third example is the combination of androstenol and androstenone that form the boar pheromone in the male pig s saliva. Both induce the sow s mating stance alone and in combination (Melrose et al., 1971). 

As a final example, consider the stereotypic standing reaction of estrous sows. This stance, which includes immobility, kyphosis, and ear pointing, is necessary for swine to copulate, and it is usually triggered by tactile cues on the back, normally from the mounting boar. As described by Signoret (1970), the response is promoted by a volatile boar pheromone (androstenone), though this odor is not normally necessary or sufficient to induce sows to adopt the stance. Rather, olfactory and auditory cues increase the probability of response. 

Men also have chemical stimulants. [14] Prelog and Ruzicka resolved the structure of 5a-androst- 16-en-3-one, the sex pheromone ofthe boar Sus scrofa domestica), [15] and, as it became clear later, also of men. [16] It is a metabolite of testosterone and its odour was described as a scent of receptacles , which had been used over a longer period to store urine. In waiting rooms, women preferred to sit rather on androstenone-impregnated chairs than on those which were untreated. Also, photographs of men, animals and houses primed with traces of 5a-androst- 16-en-3-one were considered more warm and friendlythan those which lacked the boar pheromone. 

Parrott, R.F., W.D. Booth, and B.A. Baldwin Aggression During Sexual Encounters Between Hormone-Treated Gonadectomized Pigs in the Presence or Absence of Boar Pheromones. Aggressive Behav. 11, 245-252 (1985). 

---