Dose–Response Studies for Pituitary and Testicular Function in Male Dogs Treated with the GnRH Superagonist, Deslorelin

Abstract

We tested the effect of dose of GnRH superagonist on pituitary and testicular function in a study with four groups of four male dogs. The Controls received blank implants and the other three groups received implants containing 3, 6 or 12 mg deslorelin (D-Trp6-Pro9-des-Gly10-GnRH ethylamide). In all deslorelin-treated groups, there was initially an acute increase in plasma concentrations of LH and testosterone, followed by declines such that both hormones became undetectable after approximately 12 days. There was a dose-response in some of these early aspects of the hormone profiles. With respect to long-term effects of treatment, the 12-mg dose had significantly greater effects than the smaller doses for the duration of minimum testicular volume [366 +/- 77, mean +/- SEM (3 mg), 472 +/- 74 (6 mg), and 634 +/- 59 (12 mg) days], absence of ejaculate [416 +/- 88 (3 mg), 476 +/- 83 (6 mg), and 644 +/- 67 (12 mg) days], undetectable plasma concentrations of LH and testosterone [367 +/- 64 (3 mg), 419 +/- 72 (6 mg), and 607 +/- 69 (12 mg) days], the delay until complete recovery of LH and testosterone secretion [394 +/- 65 (3 mg), 484 +/- 72 (6 mg) and 668 +/- 47 (12 mg) days], and the delay until testes had regrown to normal volume [408 +/- 77 (3 mg), 514 +/- 74 (6 mg), 676 +/- 59 (12 mg) days]. The time taken to restore full ejaculates was also longest for the 12-mg dose: 716 +/- 67 (12 mg) days vs 440 +/- 66 (3 mg) and 538 +/- 83 (6 mg) days after implantation. There was no correlation between delay to recovery of normal ejaculate quality and body mass. We conclude that the dose-response relationship with deslorelin implants is not expressed with respect to the degree of suppression of reproduction, but on the maximum duration of suppression and thus to delay until recovery.

Effects of GnRH agonist immunization on vaginal electrical resistance, FSH, LH, and ovaries in prepubertal female sheep

“…The results demonstrated that GnRH agonist immunization can promote the synthesis and secretion of FSH. Our results were consistent with the reports of Guo and Gao (2005), Junaidi et al, (2009), andGong et al (2011), but unfamiliar with other reports (Zamaratskalia et al, 2007;Li et al, 2009). Whether the efficacies of GnRHa are associated with the oestrous and/or ovulation of ewes and injection dosage of alarelin antigen needs to be further explored.…”

Development of Semen Quality Following Reversible Downregulation of Testicular Function in Male Dogs with a GnRH Agonist Implant

“…As experienced so far, reversibility accounts for all the effects resulting from hormonal castration, including semen quality (Junaidi et al. 2003, 2009; Ludwig et al.…”

Suppression of Fertility in Adult Dogs

“…Azoospermia and/or an ejaculation were observed at 60 weeks (3 mg implant) and 90 weeks (12 mg) post‐implantation (Junaidi et al. ) and after 3 months when using a 4.7 mg deslorelin implant (Romagnoli et al. ).…”

“…Complete return of semen quality to pre‐treatment values was observed by 62 (3 mg) to 102 (12 mg) weeks post‐implantation (Junaidi et al. ).…”