Rodent chemical signals

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.)... 

Novotny M., Jemiolo B. and Harvey S. (1990). Chemistry of rodent pheromones, molecular insights into chemical signalling in mammals. In Chemical Signals in Vertebrates 5 (MacDonald D. and Natynczuk S., eds.). Oxford University Press,... 

Nyby J. (1983). Volatile and non-volatile chemosignals of female rodents differences in hormonal regulation. In Chemical Signals in Vertebrates 3 (Miiller-Schwarze D. and Silverstein R.M., eds.). Plenum, New York, pp. 179-194. 

Drickamer LC (2001a) Intrauterine position effects on rodent urinary chemosignals. In Marchlewska-Koj A, Lepri JJ, Miiller-Schwarze D (eds) Chemical signals in vertebrates, vol 9. Kluwer, New York, NY, pp 211-216... 

Multiple approaches have been taken to understand the nature of pheromones in rodents. Bottom-up approaches start with assessing the effect of candidate molecules on physiological function. Top-down approaches start with a behavior and search for the chemical signals that trigger it. 

Jannett, F. J. Jr. 1986. Morphometric patterns among microtine rodents. I. Sexual selection suggested by relative scent gland development in representative voles Microtus). In Chemical signals in vertebrates (Ed. by D. Duvall, D. Muller-Schwarze, R. M. Silverstein, eds.), pp. 541—550. New York Plenum Press. 

Voznessenskaya, V.V., Parfyonova, V.M. Zinkevich, E.P. 1992. Individual odortypes. In Chemical Signals in Vertebrates 6 (Ed. by R.L. Doty D. Muller-Schwarze), pp 503—508. New York Plenum Press. Voznessenskaya, V.V, Parfyonova, V.M. Wysocki, C.J. 1995. Induced olfactory sensitivity in rodents a general phenomenon. Adv. Biosci., 93, 399-406. 

Nyby, J., 1983, Volatile and nonvolatile chemosignals of female rodents Difference in hormonal regulation, "Chemical Signals in Verte-... 

Stoddart, D. M, 1980, Some responses of a free living community of rodents to the odors of predators, i Chemical Signals Vertebrates and Aquatic Invertebrates," D. Muller-Schwarze, and R. M. Silverstein, eds.. Plenum, New York. 

In several species of rodents, the rate of sexual maturation and density of natural populations are negatively correlated (Krebs and Myers, 1974), Chemical signals discharged by females could be one of the important factors limiting reproductive activity. 

Ropartz, Ph. Chemical Signals in Agonistic and Social Behavior of Rodents. In D. Muller-Schwartze and M.M. Mozell eds. Chemical Signals in Vertebrates, p. 169-184. New York Plenum Press. 1977. 

This capacity to amplify these minute chemical signals comes with a cost, for the steroids associated with reproduction come with consequences. Even as far back as the 1930s, it was known that rodents exposed to elevated levels of estrogen, the primary feminizing sex steroid, develop mammary cancer. However, until recently, the mechanism by which steroids were linked to cancer was unclear. Elucidation of estrogen as a cancer promoter would have to wait for the development of the immortal cell lines, as explained previously. 

The best possible outcome of a bioassay is the elicitation of a specific behavior pattern by a defined chemical stimulus (Miiller-Schwarze 1977). This chapter presents methods to assess the role of chemical stimuli in the behavior of birds and mammals. An overview of the chemosensory capacities of birds and mammals to perceive stimuli is provided first, followed by a description of test paradigms that can be incorporated into bioassays. The preponderance of the chapter describes examples of these paradigms incorporated into bioassays to assess the role of chemical signals in inter- and intra-specific behaviors. The examples, like past studies in mammalian and avian chemical ecology, are disproportionately represented by rodents. Most of the described procedures, however, could be modified for other species, provided the apparatuses and the response variables can be altered to accommodate the different subject and stimuli. 

Ultra-sound emissions typically occur when male rodents are exposed to female odours or altricial neonates to maternal sources (Whitney, 1974 Conely and Bell, 1978). Without the VNO, sexually inexperienced male mice do not utter emissions at ultra-high frequencies (UHF), whereas those with prior experience vocalise after VN-x, as discussed above (Chap. 5). Female mouse urine contains a unique UHF-eliciting component which is non-volatile but ephemeral (Sipos et al., 1995). The signal is degraded by oxidation and disappears within 15 to 18 hours of deposition. Direct contact with freshly voided urine must occur before males will vocalise (sexually experienced or inexperienced). At least one of the olfactory systems is needed for UHF to be elicited by fresh urine complete deafferentation abolishes the response (Sipos et al., 1993). Exposure to females permits UHF to be elicited by other than chemical cues (Labov and Wysocki, 1989). Nocturnal or cryptic species conceivably use ultrasound to advertise male presence whether this is to deter other males or assist with female location is unclear. 

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