Estrus suppression

The influence of polymer composition and molecular weight on the estrus-suppressing activity of the microspheres in female rats was determined. A triphasic release pattern was observed. An initial rapid release over the first few days was attributed to diffusion from superficial areas of the microspheres. A second phase of lower release levels then occurs and continues until the onset of the third, major phase of release. This phase is facilitated by the onset of erosion of the polymer matrix. 

Pandey, S. D., and Pandey, S. C. (1986). Estrus suppression in wild mice source of pheromonal cue. ActaFhysiologicaHmgarica 67,387-392. 

Altrenogest 0.044 mg/kg, once daily for 15 days for estrus suppression p.o. 

Ma, W., Miao, Z. Novotny, M. 1998b. Role of the mouse adrenal gland and its mediated chemosignals in estrus suppression, the Lee-Boot effect revisited. Biol. Reprod. in press. 

Pandey, S.C., and S.D. Pandey Role of Clitorial Glands in Production of the Estrus-Suppressing Pheromone in Wild Mice. J. Reprod. Biol. Comp. Endocrinol. 4, 19-23 (1984). 

Pandey, S.D., and S.C. Pandey Regulation of Estrus-Suppressing Pheromone in Wild Mice by Ovarian Hormones. Indian J. Exp. Biol. 23,188-190 (1985). 

Figure 2a shows the daily in vitro release rate of nafarelin from a cross-linked POE polymer (Heller et al, 1987). The kinetics of release indicate a burst of drug released in the first days of testing, with the minimum level of 0.4 y g/day necessary for estrus suppression in rats maintained for approximately 130 days. These results are in good agreement with results in Fig. 2b, which shows data obtained in in vivo studies of estrus suppression, indicating release of active LHRH analog. 

Ma W., Miao Z. and Novotny M. (1998). Role of the adrenal gland and adrenal-mediated chemosignals in suppression of estrus in the house mouse the Lee-Boot effect revisited. Biol Reprod 59, 1317-1320. 

The list of pheromone controls on reproductive behavior can be extended female pheromones inhibit estrus in adult females and delay puberty in juvenile females, Lee-Boot effect male pheromones can block pregnancy, Bruce effect pheromones from dominant females can suppress reproduction in subordinate females and so on. Have a look at Wyatt s book for an abundance of examples. 

In grouped female mice ovulation and estrus are suppressed (Champlin, 1971) and pseudopregnancies occur (van der Lee and Boot, 1955). The odor of crowded female mice (eight per cage) inhibited ovulation in other females. The hormonal control of this effect has been difficult to explain. Early studies indicated that ovariectomized mice were not able to inhibit other females but in other studies, ovariectomized females still inhibited estrus in other females (Marchlewska-Koj, 1990). 

Compounds within this class of substances can inhibit hypothalamic-pituitary-ovarian axis function by inhibiting gonadotropin secretion. Subsequently ovulation and estrus is suppress leading to infertility or reduced fertility. 

One therapy includes the s.c. administration of pellets containing progesterone (200 mg) and estradiol benzoate (20mg). Although the use of 8 to 80 of these pellets has not been found to suppress normal cyclicity or behavioral estrus (McCue et al 1996), approximately 70% of the owners and trainers perceived that this produced an 80% improvement in behavior and approximately 50% perceived that there was an 80%... 

McCue P M, Lemons S S, Squires E L et al 1996 Efficacy of progesterone/estradiol implants for suppression of estrus in the mare. In Proceedings of the 42nd American Association of Equine Practitioners Annual Convention, Denver, CO, pp. 195-196... 

Some cucurbitacins have been reported to be antifertility agents. The enriched cucurbitacin extract obtained from Wilbrandia sp. was tested for its potential antifertility effects with different experimental protocols including those involving estrus cycle, implantation, abortifacient, and estrogenic/antiestrogenic activities. The extract suppressed the number of... 

MPA was used to suppress estrus in bitches.96 in addition to possible utility of oral progestagens in the "pet population," injected-MPA was used to limit the canine reservoir and vector for rabies. MA, which is being used orally to prevent estrus in bitches, is excreted rapidly from the animals.97 Rapid elimination of MA may decrease the incidence of pyometria, a side-effect which caused the removal of MPA from the market. 

Wilson (3) and Wilson and Bossert (4) divided pheromones into release pheromones (if the stimulus triggers an immediate behavioral response in the receiving organism) and primer pheromones (if the response is a long lasting one). Substances involved in alarm, territorial marking, trail, social status, sexual attraction and reproductive isolation are release pheromones while the odors involved in puberty acceleration, pregnancy block, estrus synchronization or suppression are primer pheromones. 

The male mouse produces a scent in his urine which induces and accelerates the estrus cycles of the female. This effect will be greater in females in which estrus was suppressed by aggregation. According to Nichols and Chevin (373), male urine is less effective than male presence in inducing the estrus cycle, while Gangrade and Dominic s (341) studies suggested that in contrast to the Bruce effect, the pheromone involved in the Whitten effect is a volatile substance. 

A female s estrus cycle is suppressed concomitant with simultaneous pseudopregnancy development when four or more females are put together in a absence of a male. Pandey and Pandey (343,347) concluded that the clitoral gland does not play any role in the production of the pheromone which suppresses the estrus cycles in other females and that the pheromone is thus associated directly or indirectly with ovarian hormones. 

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