Effects of gestational stress: 2. Evaluation of male and female adult offspring.

Physical restraint applied during gestation is a commonly employed animal model of human pregnancy stress. The consequences of such a paradigm have been extensively investigated in adult male rats using a variety of physiological and behavioral measures. The behavioral repertoire of female offspring, however, has been largely ignored. The current study examines adult offspring-male and female Long Evans rats (55-90 days of age) and is a follow-up report to the consequences of maternal restraint (gestation days 10 through 19) in mother rats and their juvenile offspring. Physiological measures included weight and estrous cycle regularity. Elevated plus maze and emergence tests were used to measure anxiety, and the T-maze test, cognition. Data were analyzed via hierarchical linear modeling to account for the nesting of offspring within litters. Compared to same-sex controls, males from stressed mothers displayed a progressive attenuated weight gain over experimental weeks while females from stressed mothers maintained a stable, lower weight throughout. Twenty-five percent of females in the stressed group and none in the control group displayed irregular cycles in the first week of testing; on subsequent weeks, this group discrepancy ranged from 1% to 11%. Subtle effects were observed in anxiety measures: an interaction between sex and stress group in the analysis of head dip behavior in the elevated plus maze and decreased emergence latencies in stress groups. Results demonstrate the importance of examining the effects of maternal stress in offspring of both sexes at various developmental stages.

Motor sequence learning in primate: role of the D2 receptor in movement chunking during consolidation.

Motor learning disturbances have been shown in diseases involving dopamine insufficiency such as Parkinson's disease and schizophrenic patients under antipsychotic drug treatment. In non-human primates, motor learning deficits have also been observed following systemic administration of raclopride, a selective D2-receptor antagonist. These deficits were characterized by persistent fluctuations of performance from trial to trial, and were described as difficulties in consolidating movements following a learning period. Moreover, it has been suggested that these raclopride-induced fluctuations can result from impediments in grouping separate movements into one fluent sequence. In the present study, we explore the hypothesis that such fluctuations during movement consolidation can be prevented through the use of sumanirole - a highly selective D2 agonist - if administered before raclopride. Two monkeys were trained to execute a well known sequence of movements, which was later recalled under three pharmacological conditions: (1) no drug, (2) raclopride, and (3) sumanirole+raclopride. The same three pharmacological conditions were repeated with the two monkeys, trained this time to learn new sequences of movements. Results show that raclopride has no deleterious effect on the well known sequence, nor the sumanirole+raclopride co-administration. However, results on the new sequence to be learned revealed continuous fluctuations of performances in the raclopride condition, but not in the sumanirole+raclopride condition. These fluctuations occurred concurrently with a difficulty in merging separate movement components, known as a "chunking deficit". D2 receptors seem therefore to be involved in the consolidation of new motor skills, and this might involve the chunking of separate movements into integrated motor sequences.

Effects of gestational stress: 1. Evaluation of maternal and juvenile offspring behavior.

In both humans and animals, stress experienced during gestation is associated with physiological changes and disruptions in emotional function and cognitive ability in offspring; however, much less is known about the effects of such stress in mothers. In animal models, physical restraint is commonly employed to induce stress during gestation and results in elevated postpartum maternal anxiety and changes in maternal care. The purpose of the current study was to evaluate the consequences of restraint stress applied on gestation days 10 through 19 in mother rats and their juvenile offspring. Progeny were reared by birth mothers. Preterm anxiety was assessed in the elevated plus maze and maternal behavior in the retrieval test. Cognitive (T-maze) and anxiety measures (elevated plus maze and emergence) were applied to a subset of male and female offspring at 30-31 days of age. Weight and litter characteristics were also recorded. Mother rats exposed to stress during gestation had attenuated weight gain, elevated anxiety-like behavior, and reduced maternal care. Stressed mothers also had fewer pups and an elevated offspring mortality rate. The consequences of gestational stress in offspring were subtle and gender-dependent. Only juvenile females displayed marginal effects of gestational stress in the form of elevated anxiety-like behavior and attenuated weight gain. In the current study, although gestational stress had robust effects in the mother rat, these did not translate to similar changes in offspring behavior. The importance of focusing research on maternal responses to gestational stress is highlighted by these findings.