Effect of the GnRH antagonist, acyline, on early estrous cycle and pregnacy in the domestic cat.

A RISSO; P.E. DE LA SOTA; J.D. DIAZ; A JIMÉNEZ ; E JUAREZ; C GOBELLO

Congreso; Morris Animal Foundation's Annual Meeting 2010; 2010

Morris Animal Foundation's

Gonadotrophin  releasing  hormone  (GnRH)  antagonists  competitively  block  GnRH  receptor  Objetive: To  investigate  the effects and clinical  safety of  the GnRH antagonist acyline  in cats, when administered during  the proestrus (Experiment I) and pregnancy (Experiment II)sites  in the  adenohypophysis,  exerting  an immediate inhibitory action on the gonadal axis. I. Seven postpubertal queens, in a total of 24 proestrus (< 3 d) periods, randomly assigned to acyline (330 mg/kg sc,   NIH, USA; ACY, n = 17) or placebo sc; PLC; n = 7). Follow up: Behavioral patterns in the presence of a tom cat,  vaginal cytology, P4 (14 d after estrus termination) ng/ml) and ultrasound pregnancy  diagnosis. II. Fourteen pregnant queens randomly assigned to the following groups: early pregnancy group acyline from pregnancy diagnosis to 25 d post mating (ACY-E; n = 3), mid pregnancy group acyline 26–45 d post mating (ACY-M; n = 4), late pregnancy group acyline  >45 d post mating (ACY-L; n = 3); and PLC (placebo, n = 4). Follow up: Ultrasonography every 2 d for 14 d, to detect resorption or abortion. P4 on days -1, 7, and 14. I. Matings were confirmed in all the cases. Intervals treatment to cessation of estrus : 7.0 + 1.3 and PLC: 7.0 + 1.7 d (P   > 0.1) for ACY and PLC, respectively. Ovulation occurred ACY: 2/17  and PLC: 7/7 (P < 0.05). In the ACY 1/16 that were mated and PLC 7/7 became pregnant  (P < 0.05. The  interval between  treatment and onset of next proestrus was 18.4 + 1.7 d  for  the 14 nonovulating queens  treated with ACY. II. All 14 pregnant queens maintained pregnancy. Progesterone serum concentrations did  not  differ  among  treatment  subgroups  (early, mid,  and  late)  throughout  the trial (P > 0.1). In cats, the GnRH antagonist acyline prevented ovulation, although ongoing ovarian follicular development and gestational corpora lutea were not affected by the gonadotrophin with drawal induced by this treatment.