Priming pheromones

Bronson F. and Coquelin A. (1980). The modulation of reproduction by priming pheromones in house mice speculations on adaptive function. In Chemical Signals in Vertebrates 2 (Miiller-Schwarze D. and Silverstein R.M., eds.). Plenum, New York, pp. 243-266. 

Hurst J.L. and Nevison C. (1994). Do female house mice, Mus domesticus, regulate their exposure to reproductive priming pheromones Anim Behav 48, 945-959. 

Izard M.K. and Vandenbergh J.G. (1982a). Priming pheromones from oestrous cows increase synchronisation of estrous in dairy heifers after PGF-2a injection. J Reprod Fertil 66, 189-196. 

Pheromones have been classified as a function of their effect. Those triggering immediate behavioral effects were termed releasing pheromones, while those altering slower processes of physiological or developmental nature were termed priming pheromones (Wilson and Bossert 1963). The rabbit MP has a clear releasing function but recent data also show that it has another function that cannot be termed priming in the classical sense. 

In some cases, commercial use has been made of reproductive pheromonal effects. For example, spraying sows with synthetic 5a-androstenone, a steroid sold under the trade name Boar Mate, helps to ready the animal for mating with a boar. 5a-Androstenone is one of two steroids in the saliva of the boar that primes the sow for mating. 

Mice are able actively to seek or avoid priming pheromones that modulate their ovarian cycle and onset of puberty. Peripubertal female mice avoid the urine odor of adult males, known to accelerate puberty in females, and are more attracted to the odor of grouped adult females. This behavior is particularly effective because the active space of the (almost) non-volatile male pheromone is small, and prolonged exposure is required for the effect to occur (Coppola and O Connell, 1988). Likewise, prepubertal female mice do not urinate near urine marks of adult males, while grouped, estrous, and diestrous adult females do. Such behavior may help young females to avoid exposure to male odors until they reach puberty. This way they would be protected from mating too early, and their eventual reproductive success would be enhanced (Drickamer, 1989a). 

The main olfactory system mediates munerous behaviors that will be discussed in the section on signaling and priming pheromones, and also... 

Signaling pheromones are animal-produced, interindividual chemicals that modulate behavior in conspecifics. Like visual and auditory signals, they have comparatively rapid effects exchange of signals takes seconds or minutes. (Priming pheromones [Ch. 8], hy comparison, trigger slower endocrine or developmental processes.) The pheromone concept, originally based on insects (Karlson and Luscher, 1959), has been debated for vertebrates, notably mammals (e.g. Beauchamp etal., 1976 Johnston, 2001). Often it is better to use the term body odors to avoid particular assumptions. Now the term pheromones is widely used for vertebrates, without any particularly narrow definition implied. 

Chemical cues are important to advertise one s sex and to attract the opposite sex as the first step in sexual behavior. Other functions of sexual signals are to signal current sexual status and to alter the behavior of the potential partner(s) via courtship or scent marking to facilitate mating. Typically, the odor of the opposite sex is attractive, at least in the breeding season. (Priming pheromones are covered separately in Chapter 8.)... 

Milt production in male carp Cyprinus carpio) can be similarly stimulated by females and possibly a pheromone (Billard etal., 1989). Table 8.1. summarizes some priming pheromones in fish. 

Rats ovulate when exposed to soiled bedding from males. The stimulus is nonvolatile, as a wire screen can eliminate this response. Vomeronasal organ occlusion reduces the response, implicating this pathway for priming pheromone reception in this species (Johns etal., 1978). Table 8.2 summarizes the role of the vomeronasal in priming effects in rodents. 

FIGURE 8.4 The Bronson model of priming pheromone actions in rodents. Chemical signaling between males and females constitutes a feedback mechanism that results in accelerated maturation and reproduction. This, in turn, permits the mice to adjust their reproduction and population size quickly to respond to environmental conditions such as sudden food abundance at harvest time. FSH, follicle-stimulating hormone LH, luteinizing hormone PRL, prolactin. Stimulation and inhibition are marked by - - and —, respectively. (From Bronson and Coquelin, 1980.)... 

Priming pheromones hold great promise as means to accelerate puberty or to synchronize and regularize estrus cycles in livestock. 

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