Table 6.

Principal elements of EPA and OECD guideline developmental neurotoxicity study ^a .

P-generation females (number per dose level)
No. females assigned b	GD 0 = the day of insemination	25–30
Detailed clinical observations	≥2 × each gestation and lactation	10
F1 males and females (no. males and females; ≥20 litters/dietary level) c
Detailed clinical observations	PND 4, 11, 21, 35, 45, and 60	10–20
Body weight	PND 4, 11, 17, and 21 and at least once every 2 wks thereafter	All pups/litter
Sexual maturation (preputial separation and vaginal patency)	Daily from before initiation until landmark is achieved	All pups/litter
Motor activity	PND 13, 17, 21, and ∼PND 60–70	10–20 d
Acoustic startle	Around the time of weaning and ∼PND 60–70	10–20
Cognition	Post-weaning and PND 60–70	10–20
Brain measurements	PND 11 or 21–22 Term (∼PND 70)	10 10
Neuropathologye	PND 11 or 21–22 Term (∼PND 70)	10 10

^a Test materials administered via the diet or by gavage (acetamiprid) to P-females from GD 0 or 6 to LD 21 (see text for details).

^b 25–30 untreated female rats per dietary level were co-housed with untreated males to obtain ≥20 litters per dose group.

^c F1 males and females from each litter were randomly assigned to a test set, with each litter represented by at least one male or one female (≥20 litters per dose level).

^d EPA (1998) requires one male OR one female per litter (minimum 20 litters) and OECD (TG 426) requires one male AND one female per litter (minimum 20 litters) for neurobehavioral endpoints.

^e An example of neuropathology procedures used in these studies is provided in Supplementary material (Appendix I).