Previously, we have shown that rats administered MDMA from postnatal (P) days 11-20
had reductions in body weight during the period of treatment and as adults they had
deficits in sequential and spatial learning and memory. In the present study, to control
for weight reductions, we used litters with double the number of offspring to induce
growth restriction comparable to that of standard size litters treated with MDMA.
Litters were treated twice daily from P11 to 20 with vehicle or MDMA (20 mg/kg) or
only weighed. Males, but not females, exposed to MDMA had longer latencies and more
errors in the Cincinnati water maze compared to males of the other treatments. In
the Morris water maze (210 cm pool, 10x10 cm platform), the MDMA animals were impaired
relative to all other treatments during acquisition. Only the MDMA females showed
deficits when the platform was shifted to a new location, however, both MDMA males
and females were impaired when the location of the platform was again shifted and
a reduced platform (5x5 cm) used. No differences were observed in the ability to swim
a straight channel, locate a platform with a cue, or the endocrine response to forced
swim among the treatment groups. No differences were seen between animals injected
with saline and those only weighed. The data suggest that factors, such as growth
retardation, multiple injections, or the composition of the litter, do not affect
the development of learning and memory impairments resulting from P11 to 20 MDMA exposure.
The large litter approach offers a novel method to control for undernutrition during
the preweaning period in rodents.