Behavioural teratology: post-natal consequences of drug exposure in utero

The effects of pre-natal exposure to drugs that subsequently affect the post-natal behaviour without apparently causing noticeable brain damage forms the subject of behavioural teratology. This review summarizes the experimental studies of several investigators who showed that pre-natal administration of such psychotropic drugs as meprobamate, isocarboxazid and reserpine reduced the maze-learning ability of the mature offspring. A more detailed survey of the effects of D-amphetamine and diazepam is then given. Both drugs were not foetotoxic and only caused appreciable changes in locomotor activity of the offspring at least 14 days after birth. With the amphetamine treated rats, these changes were biphasic (elevated at 15 days and reduced at 21 days) whereas the diazepam treated animals showed a reduction in locomotor activity for at least 21 days after birth. The results of our own studies, and those of others, do not enable a correlation to be made between the effects of the various drugs on the development of specific central neurotransmitters and the behavioural deficits noticed. The review concludes with an outline proposal for screening drugs for their potential as behavioural teratogens. The possible mechanisms whereby behavioural teratogens may cause subtle changes in the maturation of the brain are also outlined.