In vivo imaging in the rabbit as a model for the study of ovulation-inducing factors

Abstract

The study of factors responsible for eliciting ovulation in rabbits has been hampered by the lack of a suitable method of monitoring the ovaries in vivo. Ovarian imaging by ultrasound biomicroscopy was used in two experiments designed to determine the effects of seminal plasma on the ovulatory response in rabbits. In Experiment 1, female rabbits were group-housed and treated intramuscularly with saline, gonadotropin releasing hormone (GnRH), or seminal plasma of llamas or rabbits (n = 4 to 6 per group). Rabbits were euthanized eight days later to evaluate the ovarian response by ultrasound biomicroscopy ex situ. No differences among groups were detected in the proportion of rabbits that ovulated or in the number and size of corpora lutea. The high incidence of ovulation in the negative control group was unexpected, and confounded determination of an ovulation-inducing effect of seminal plasma. In Experiment 2, female rabbits were caged individually, and treated as in Experiment 1 (n = 5 to 7 per group). The ovarian response was evaluated in vivo by transcutaneous ultrasound biomicroscopy. Ovulation and formation of corpora lutea were detected only in rabbits given GnRH. A preovulatory surge in plasma luteinizing hormone concentration and a post-ovulatory rise in plasma progesterone concentration were detected only in rabbits treated with GnRH. Surgical translocation of the ovaries to a subcutaneous position enabled longitudinal assessment of the ovulatory response by ultrasound biomicroscopy. Results clearly documented the effect of physical/social interaction on ovulation in rabbits, and did not support the hypothesis that seminal plasma elicits ovulation in rabbits.

Ovulation‐inducing factor (OIF/NGF) in seminal plasma: a review and update

“…Seminal plasma treatment was, however, associated with an increase in the number of antral follicles and the presence of large haemorrhagic anovulatory follicles (Silva, Niño et al., ), similar to that observed after ovarian superstimulation of does with eCG (Garcia‐Ximenez & Vicente, ; Mehaisen, Vicente, Lavara, & Viuedes‐de‐Castro, ). Seminal plasma treatment, however, did not elicit a detectable increase in plasma LH concentration in rabbits (Cervantes et al., ). The role of other behavioural/physical stimuli was readily apparent in the latter study wherein the incidence of ovulation was equally high (i.e.…”

“…Despite that rabbits are the most widely studied induced ovulator and the first species to be identified as such more than 100 year ago, the principal stimulus responsible for triggering ovulation in rabbits is still unclear. Recently, OIF/NGF has been found in high concentration in rabbit seminal plasma (Casares‐Crespo, Talaván, & Viudes‐de‐Castro, ; Maranesi et al., ; Silva, Niño et al., ), but intramuscular administration of neither rabbit nor llama seminal plasma‐induced ovulation in receptive does (Cervantes, Palomino, & Adams, ; Silva, Niño et al., ). Seminal plasma treatment was, however, associated with an increase in the number of antral follicles and the presence of large haemorrhagic anovulatory follicles (Silva, Niño et al., ), similar to that observed after ovarian superstimulation of does with eCG (Garcia‐Ximenez & Vicente, ; Mehaisen, Vicente, Lavara, & Viuedes‐de‐Castro, ).…”

Gene Expression and Localization of NGF and Its Cognate Receptors NTRK1 and NGFR in the Sex Organs of Male Rabbits

“…), while others do not seem to confirm the efficacy of seminal plasma as an ovulation‐inducing factor in rabbits (Cervantes et al. ). Nevertheless, it is highly expected that NGF can modulate sperm functions also in the rabbit (Jin et al.…”

“…However, in principle, we cannot be ruled out that an ovulatory response may be elicited by the ovulation-inducing factor existing in the seminal plasma of this species, as already found in llama and alpacas (Silva et al 2011). Studies about this subject are still inconclusive, given that some support such evidence (Silva et al 2011;Rebollar et al 2012), while others do not seem to confirm the efficacy of seminal plasma as an ovulationinducing factor in rabbits (Cervantes et al 2014). Nevertheless, it is highly expected that NGF can modulate sperm functions also in the rabbit (Jin et al 2010).…”

A comparative study on the embryo-fetal development in rabbits after artificial insemination

“…This phenomenon is correlated to the appearance of antibodies in the plasma of certain treated female animals. Cervantes [46] reported that the maintenance of the corpus luteum function is dependent on the presence of the conceptus and estradiol further, stating that the primary trigger for ovulation induction in rabbits has not been well understood, but a major role is played by the pituitary gland in ovulation occurrence.…”