Susan M. Barlow

Plasma corticosterone responses to stress following chronic oral administration of diazepam in the rat

The effect of daily, oral administration of diazepam on plasma corticosterone responses to stressors of varying intensity was investigated. In rats exposed to the mild stress of noise, diazepam, 10 mg kg−1 but not 1.0 or 0.1 mg kg−1, reduced plasma corticosterone concentrations by 30% in comparison with controls. However, in rats exposed to the more severe stressors, foot‐shock or immobilization, none of these doses of diazepam reduced plasma corticosterone responses. In unstressed rats, diazepam 10 mg kg−1 raised plasma corticosterone concentrations. It is suggested that plasma corticosterone concentrations are not a reliable indicator of the tranquillizing effect of diazepam during stress.

Effects of stress and adrenocorticotrophin administration on plasma corticosterone levels at different stages of pregnancy in the mouse.

Stress or administration of ACTH to pregnant mice gave rise to much higher plasma corticosterone levels in the second half of pregnancy than in the first half, suggesting that there may be increased adrenal sensitivity to ACTH or decreased metabolism of corticosterone during the second half of pregnancy.

Teratogenic effects of Silastic intrauterine devices in the rat with or without added medroxyprogesterone acetate.

The teratogenicity of intrauterine devices (IUDs) made of silicone rubber (Silastic, Dow Corning Corporation, Midland, MI) with or without added medroxyprogesterone acetate (MPA) has been investigated in the rat. Small rod-shaped IUDs were inserted into the uterus, one between each embryo, on day 9 of pregnancy and left in place until the rats were killed just before term for examination of the fetuses. MPA exposure caused masculinization of the external genitalia of female fetuses and feminization of the external genitalia of male fetuses. There was no increase in other, nongenital malformations in MPA-exposed fetuses, compared with fetuses exposed to Silastic alone, but both Silastic-exposed groups had significantly more malformations than untreated control rats. In a second experiment, a significant increase in malformations in fetuses exposed to Silastic alone, compared with untreated control fetuses, was confirmed. The malformation rate in control rats that underwent sham operations was not significantly increased, compared with untreated control rats.

Occupational, industrial and environmental agents

Abstract Many chemicals and agents found in occupational and industrial settings as well as detected in the environment are discussed in relationship to their effects on mother and embryo/fetus during pregnancy. Recommendations are offered in terms of monitoring of such exposures and what actions should be taken to modify exposures to such agents during the pregnancy. Of special note are discussions of exposures to solvents, pesticides, phenoxyacetic acid derivatives, polychlorinated dibenzo-dioxins, polychlorinated biphenyls, chlorinated drinking water by-products, metals, substances in toxic waste landfill sites, in photography, in nuclear sites, in electromagnetic radiation, in cell phones, and following electric shocks/lightning strikes.