Stereotypic behavioral response of rat fetuses to acute hypoxia is altered by maternal alcohol consumption

Discovery and development of a new class of potent, selective, orally active oxytocin receptor antagonists

We report a novel chemical class of potent oxytocin receptor antagonists showing a high degree of selectivity against the closely related vasopressin receptors (V1a, V1b, V2). An initial compound, 7, was shown to be active in an animal model of preterm labor when administered by the intravenous but not by the oral route. Stepwise SAR investigations around the different structural elements revealed one position, the arenesulfonyl moiety, to be amenable to structural changes. Consequently, this position was used to introduce a variety of substituents to improve the physicochemical properties. Some of the resulting analogues were found to be superior to 7 both in terms of potency in vitro and aqueous solubility, which translated into significantly improved efficacy in the animal model after intravenous and oral administration. The best compound, 73, potently inhibited oxytocin-induced uterine contractions in nonpregnant rats and reduced spontaneous uterine contractions in late-term pregnant rats.

Fundamental motor patterns of the mammalian fetus

Techniques that permit direct observation of fetuses in vivo recently have expanded our understanding of prenatal behavioral development in mammals. Although fetal motor activity seems to lack the dynamic, goal-directed character of postnatal behavior, the dimensions that define behavioral organization after birth are applicable to the movements expressed by fetuses. Fetal activity exhibits temporal, sequential, and spatial organization that emerges between the inception of movement and term. Fetal rodents, for example, exhibit coordinated motor patterns antecedent to postnatal righting, locomotion, suckling, maternal-infant communication and grooming behavior, while other action patterns appear to be functional adaptations to the intrauterine niche. Fetuses also are behaviorally responsive to sensory stimulation and changes in environmental conditions in utero. Expression of these behavioral properties emphasizes continuity between prenatal and postnatal life while implying an adaptive role for behavior before birth.

Behavioral response of altricial and precocial rodent fetuses to acute umbilical cord compression

Norway rat fetuses (Rattus norvegicus) exhibit a stereotypic behavioral response when the umbilical cord is experimentally compressed with a vascular clamp. In this study, the development of the fetal behavioral response to cord compression was compared in altricial and precocial rodents, which differ markedly in neural and motor maturity at the time of birth. Both altricial and precocial species showed some form of behavioral response to umbilical cord compression. Fetuses of two altricial species, Norway rats and Mongolian gerbils (Meriones unguiculatus), expressed hyperactivity in response to cord compression throughout the last third of gestation. In contrast, precocial cotton rats (Sigmodon hispidus) and spiny mice (Acomys cahirinus) did not respond to cord compression until relatively late in gestation. Thus, altricial and precocial species do not express the cord compression response during comparable periods of neural development: precocial species are much more mature at the earliest expression of this behavior than altricial species. These findings are consistent with the interpretation that the cord compression response is a behavioral adaptation that can promote survival of the fetus in utero.

The effect of prenatal cocaine exposure on umbilical cord length in fetal rats

Umbilical cord length has been considered a reliable indicator of fetal movement. In this study, the effect of prenatal cocaine exposure on umbilical cord length was examined in rats. Pregnant rats were intubated with either 0 or 60 mg/kg cocaine hydrochloride daily from gestation day (GD) 14-21. Fetuses were removed via Caesarean section on GD 21 and umbilical cord length, placental weight and fetal body weight were measured. Fetuses exposed to cocaine in utero had significantly shorter umbilical cords than intubated controls, although there were no differences in placental or fetal body weights. These data suggest that prenatal cocaine exposure suppresses fetal movement, which could contribute to some of the long-term effects observed in cocaine-exposed offspring.

Response of the rat fetus to acute umbilical cord occlusion: an ontogenetic adaptation?

Occlusion of the umbilical cord on days 19, 20 or 21 of gestation results in a stereotypic behavioral response by the rat fetus. The intensity of this response is diminished in older fetuses. Abrupt changes in fetal heart rate accompany the behavioral response to hypoxia. Changes in fetal activity and heart rate appear to be dissociated, however, because bradycardia immediately after umbilical cord occlusion is more pronounced in older fetuses. The possibility that these behavioral and cardiac responses to hypoxia are ontogenetic adaptations restricted to the prenatal period is discussed.