Interruption of the canine estrous cycle with the low and high dose of the GnRH antagonist, acyline

VALIENTE C., GARCÍA ROMERO G., CORRADA Y., DE LA SOTA P.E., HERMO G., GOBELLO C.

THERIOGENOLOGY

ELSEVIER SCIENCE INC

Año: 2009 vol. 71 p. 408 - 411

0093-691X

To test the efficacy and clinical safety of a low and high dose of the GnRH antagonist, acyline, on estrous cycle interruption and anovulation in female dogs, twenty proestrous (< 3 days) bitches were randomly assigned to one of the following pharmacological sc protocols: acyline (NICHHD, NIH, USA) 110mg/kg (ACY-L; n = 6), acyline at 330mg/kg (ACY-H, n = 8) or placebo (PLACE, n = 6). The animals were followed up daily by clinical and vaginal cytology examination during 60 days. Blood samples for progesterone (P4) serum determinations were collected on day 14 after treatment to test ovulation. Appearance of side effects and days to the onset of the first  spontaneous estrous cycle after treatment were also recorded. Both ACY groups but not the PLA interrupted their estrous cycles after treatment (P < 0.05). Time to achieve estrus interruption in ACY-L and ACY-H groups were 3 ± 0.6 and 3.2 ± 02, respectively (P > 0.05). In the PLACE bitches physical, behavioral and cytological proestrus slowly progressed to estrus and diestrus. Ovulation was absent in all ACY but not in PLACE bitches (P< 0.05). None of the females presented side effects related to the treatments (P > 0.05). Spontaneous return to normal estrous cycle after treatment occurred in all ACY (ACY-L 19.5 ± 2.7 vs. ACY-H 24.8±2.0; > 0.05) but in none of the PLACE animals (< 0.05). It is concluded that acyline efficiently, safely and reversibly interrupted early estrous cycle blocking ovulation in these animals.