Canine uterine artery hemodynamic during Bromocriptine-induced estrus

Bromocriptine ((BRM); as a dopaminergic agent) reduces the serum prolactin, and is one of the most routine drugs to induce a successful estrus cycle in bitches. Some clinical side effects are accompanying this drug. This study aimed to investigate the hemodynamics of the uterine artery (UA) following administration of the increasing doses of BRM. In a case-control study, five non-pregnant bitches of mixed breeds in the anestrus stage received daily oral doses of BRM on days 1 and 2 (100, µg/kg), days 3 and 4 (200 µg/kg), and days 5 onward (400 µg/kg) until turning into proestrus. Three bitches, with expressed estrus without any intervention, were considered as control. The vaginal cytology, the ultrasound examination, and the serum progesterone (P4) assay were performed at 2-3 day intervals. Proestrus was induced within 6.6±1.17 days following BRM treatment. BRM significantly lowered the serum P4 to 15.1±0.78 compared to the control group (21.5±1.13 ng/mL) during induced estrus. BRM significantly changed UA hemodynamics over the days before proestrus. Mean UA pulse index, resistance index, and peak systolic velocity in BRM-induced estrus were significantly lower than the control group. The results of this study showed lower serum P4 levels and some alterations in the canine uterine hemodynamic during BRM-induced estrus compared to naturally expressed estrus. Induced cycle in dogs with lower serum P4 levels and altered UA hemodynamics must be considered for subsequent pregnancy outcomes in the BRM induced-estrus.