| Study Type | Purpose | Protocol | Endpoints | Limitations | Reference |
|---|---|---|---|---|---|
| Single-generation reproduction | Provides basic information on potential of agent to produce adverse effects on male and female reproduction | Before mating, males exposed for complete cycle of spermatogenesis and epididymal transit time; females exposed for at least 2 estrous cycles | Toxic effects, mortality, neurobehavioral changes, altered sexual behavior, problems in parturition and lactation, time to positive sperm smear, duration of pregnancy, number and sex of pups, stillbirths, live births, presence of gross abnormalities, weight changes, and structural abnormalities | Does not provide information on breeding capacity of the F1 generation, effects expressed after weaning, individual male and female effects, reproductive senescence, reversibility, other specific functional developmental effects, time of effect initiation, structural anomalies of offspring (generally), internal dose | OECD 1983 |
| Multi-generation reproduction | Determines potential of agent to produce adverse effects on male and female reproductive systems and on the embryo, fetus, and neonate | Before mating, males and females exposed 10 wk; offspring exposed through lactation and after weaning, by individual treatment; dosing of all generations is continuous throughout study | Libido; estrous cyclicity, ovarian histopathology including quantification of primordial follicles in P and F1 females; sperm parameters (count, motility, morphology) in P and F1 males; fertilization; implantation; embryonic, fetal, neonatal growth and development; parturition; lactation; post-weaning growth and sexual maturity; development of reproductive organs; brain, spleen, and thymus weights | Does not provide information on reproductive senescence, reversibility, detailed functional developmental effects other than on the reproductive system, time of effect initiation, structural anomalies of offspring (generally) | OECD 2000b; FDA 2000; EPA 1998b |
| Prenatal developmental toxicity | Determines potential of agent to produce adverse effects on animals exposed during gestation | Animals (rodent and nonrodent) exposed at least from implantation until just prior to parturition | External visceral and skeletal malformations and variations, weight, pre implantation and post-implantation loss | Does not provide information on reversibility and repair of specific effects, malformed offspring may die before observation, low power for detecting malformations, treatment does not usually cover period before implantation, function of fetal organs not evaluated, restricted macroscopic examination, specific susceptible period of development can not be identified, limited evaluation of maternal and adult toxicity | OECD 2000a; EPA 1998a; FDA 2000 |
| Developmental neurotoxicity | Assesses potential neurotoxicity from exposure during critical stages of development | Pregnant animals exposed during gestation and lactation to postnatal day 10 | Offspring tested for gross neurological and behavioral disorders, motor activity, response to auditory startle, learning and memory, neuropathological effects, brain weight | Exposure over whole period of postnatal development is not included, limited assessment of learning and memory | EPA 1998c |
| Serial mating (Dominant lethal) | Assesses stages of spermato genesis and cell types in male reproduction for sensitivity to an agent | Adult males exposed for 1-5 d before mating then mated to 1-3 females weekly for 8-10 wk | Number of implantation sites in uteri, early fetal mortality | Does not provide information on reversibility, several general reproduction parameters as stated under the limitations section of the single- and two-generation reproduction studies, and endpoints of male reproductive toxicity | OECD 1984; EPA 1998d |
| Continuous breeding (RACB) | Similar to multigeneration except that reproductive capacity over a 14-wk is also assessed | Males and females (rats and mice) treated for 1 wk before mating and for 14-wk mating period. Litters removed at birth, examined, and discarded, except for last litter which is weaned, raised to breeding age, and mated to evaluate effects in second generation | Same as those in the multigeneration studies, as well as time between litters and progressive effects on fertility and reproduction | Does not provide information on individual male and female parental effects; reversibility; specific functional developmental effects in offspring, time of effect initiation, internal and skeletal anomalies in offspring, sexual behavior | Reviewed in Lamb 1985 |
| Total reproductive capacity | Assesses ovarian toxicity | Females (usually mice) exposed to an agent for a short period in utero or post-natally and allowed to mate with a single male while female remains fertile | Number of litters and offspring | Does not provide information on reversibility types of toxicity other than ovarian, effects in males | Mc Lachlan et al. 1981; Generoso et al. 1971 |
From: Appendix D, Experimental Animal and In Vitro Study Designs
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