Differential effect of restraint procedure on incidence of restraint-stress-induced rib fusion in CD-1 mice

Abstract

In an investigation of the effects of specific maternal Stressors on development of the conceptus, pregnant mice were exposed to restraint stress on gestation day 9 (plug = day 1). Mated females were either unrestrained (C), unrestrained and food/water deprived (FWD), or restrained with surgical tape in a supine position for 12 h by one of two methods: I. 1-inch wide tape reaching from each shoulder across the body to the opposite thigh, or II. 1-inch wide tape placed over one shoulder, across the thorax, and over the opposite shoulder and similar tape placed over each thigh and across the intervening pelvic area. For both methods, an additional tape was placed across the tail and a 2-inch wide tape secured the upper abdominal area. There were 32 to 62 litters in each treatment group, and all fetuses were examined on day 18 for gross and skeletal defects. With regard to rib fusion, the percentage of affected fetuses and litters was increased ( P ≤ 0.05) by Method I (3.5% and 27%, respectively) vs. Method II. (0.5% and 4%), C (0.1% and 1%), or FWD (0%). Incidences of supernumerary ribs, however, did not differ between the restrained groups but were higher in both such groups than in the FWD and C groups. These results suggest that different methods of restraint may result in differences in incidence of rib fusion. Such data suggest that development of the offspring of stressed dams may be significantly influenced by what might appear to be minor differences in the stress techniques used.