A rapidly reversible effect of a single dose of phenoxybenzamine on the fertility of male rats

Detection of Effects on Male Reproduction—A Literature Survey

The 1CH (International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use) Guideline for Detection of Toxicity to Reproduction for Medicinal Products, adopted at the Second ICH Conference in Orlando, FL, U.S.A., emphasized the need for research into the suitability of various methods for the detection of effects on fertility in males. The current project was undertaken to compare the efficiency of methods by evaluating reports in the open literature. The results of the examination of 117 substances or substance classes support the view that histopathology and organ weight analysis provide the best general-purpose means of detecting substances with the potential to affect male fertility. Examinations at up to 4 weeks of treatment appear to be as effective as examinations conducted at later times. Mating with females for detection of effects unrelated to interference with sperm production appears to provide an optimal combination because adding other methodologies does not materially improve the detection rate. As to the timing of the mating trial, a 2-week premating period is as efficient as mating at 4 weeks and apparently more efficient than mating after prolonged premating treatment.

Effect of prazosin on sperm transport in male rats

Our objective was to investigate ejaculation and transport of sperm in the reproductive tract of male rats treated with an alpha-adrenergic receptor antagonist. Males were dosed (s.c.) with vehicle or 1.4 mg/kg prazosin. Sperm recovered in utero and ex vivo from the vas deferens and cauda epididymis were evaluated. Mating behavior and sperm motility were unaffected by prazosin. Prazosin treated males ejaculated fewer sperm (12.58 +/- 8.12 vs. 110.5 +/- 29.15 million), and the distal vas deferens contained fewer sperm (2.72 +/- 0.84 vs. 24.42 +/- 3.25 million) relative to controls. Prazosin-treated males had more sperm in the cauda epididymis relative to controls indicating inhibition of sperm transport to the vas deferens. These data demonstrate that inhibition of sperm transport from the cauda epididymis to the distal vas deferens is related to low ejaculate sperm counts in prazosin treated rats.