Comparison of anxiety-like behavior in adolescent and adult sprague-dawley rats.

The conditions under which age differences in anxiety are observed in rodents are unclear. These studies explored the influence of test condition on anxiety-like behavior in adolescent and adult rats using the light-dark box. Behavior was assessed under different illumination levels (30 or 60 lux) and after brief stress (restraint or bright light). Anxiety-like behavior did not differ in the 30-lux test but was increased in adolescents in the 60-lux test. Restraint increased anxiety-like behavior in adolescents, resulting in elevated anxiety-like behavior relative to adults. Bright light decreased anxiety-like behavior, possibly because of negative contrast or novelty-induced anxiolysis. These studies demonstrate that adolescents display increased anxiety-like behavior when test conditions are more aversive and following exposure to stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cocaine treatment and prenatal environment interact to disrupt intergenerational maternal behavior in rats.

The link between impaired maternal behavior (MB) and cocaine treatment could result from drug-induced decreases in maternal reactivity to offspring, prenatal drug exposure (PDE) in offspring that could alter their ability to elicit MB, or the interaction of both, which could subsequently impair MB of the 1st-generation dams. Following chronic or intermittent cocaine or saline treatment during gestation, rat dams rearing natural or cross-fostered litters were compared along with untreated dams for MB. Untreated 1st-generation females with differentially treated rearing dams and PDE were tested for MB with their natural litters. The authors report disruptions in MB in dams and their 1st-generation offspring, attributable to main and interaction effects of maternal treatment, litter PDE, and rearing experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early-life maternal separation and social isolation produce an increase in impulsive action but not impulsive choice.

Early life environment, events, and context, such as mother–offspring relationship, can have profound effects on future behavior and physiology. We investigated the effects of long-term maternal and social separation, through artificial rearing, on adult impulsivity. Rats were maternally reared (MR) or artificially reared (AR) and half of the AR rats were provided with replacement somatosensory stimulation intended to simulate maternal licking. There are at least 2 forms of impulsivity and we compared rats on 1 test of impulsive action (differential reinforcement of low rates of responding—DRL-20s) and 2 tests of impulsive choice (delay discounting and fixed consecutive number schedule—FCN). We found that AR rats are more action impulsive; however, this effect can be reduced by maternal licking-like stimulation. In contrast, AR rats did not display an increase in impulsive choice. Overall, these experiments show that early life maternal and social separation have different effects on the 2 forms of impulsivity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Artificial rearing causes changes in maternal behavior and c-fos expression in juvenile female rats.

This study investigated the effects of early-rearing experiences on responsiveness to pups and on the pattern of c-fos activation in the brain of juvenile female rats. From Days 4 to 20, littermate females were reared with their mothers (MR) or artificially (AR). AR rats received minimal licking-like tactile stimulation (AR-min) or maximal stimulation (AR-max). On Day 20, rats were exposed to pups for 4 or 8 days, exposed to a playmate for 4 or 8 days, or left in isolation for 4 or 8 days. Compared with MR rats, pup-exposed AR rats engaged in less pup licking, and all AR rats showed significant reductions in c-fos immunoreactivity in the medial preoptic area and the parietal and piriform cortices. The AR-min group showed the greatest difference in Fos-lir compared with the MR groups. Possible mechanisms that mediate the effects of rearing on the development of neural circuits underlying maternal behavior are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal handling on play behavior and fear towards a predator odor in juvenile rats (rattus norvegicus).

The effects of brief daily separation, also known as "handling," during the first 2 weeks of life on play behavior and fearfulness toward a predatory odor were assessed in juvenile rats. Handled rats were more playful than nonhandled control rats, and while handling had no effect on the direct response of these rats toward a predatory odor, handled rats did not exhibit a conditioned suppression of play when tested later in the same context where they had been exposed to the predatory odor. Handled rats were still wary of the environment in that they continued to show a heightened level of risk assessment behavior. These data suggest that early postnatal experiences may play a significant role in determining how an animal deals with predatory threats later in life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of D1 or D2 dopamine receptor antagonism in the medial preoptic area, ventral pallidum, or nucleus accumbens on the maternal retrieval response and other aspects of maternal behavior in rats.

The medial preoptic area (MPOA), ventral pallidum (VP), and nucleus accumbens (NA) receive dopaminergic afferents and are involved in maternal behavior. Experiments investigated whether dopamine (DA) receptor antagonism in NA disrupts maternal behavior, determined the type of DA receptor involved, and investigated the involvement of drug spread to VP or MPOA. Injection of SCH 23390 (D1 DA receptor antagonist) into NA of postpartum rats disrupted retrieving at dosage levels that were ineffective when injected into MPOA or VP. Motor impairment was not the cause of the deficit. Injection of eticlopride (D2 DA receptor antagonist) into NA or VP was without effect. Results emphasize the importance of DA action on D1 receptors in NA for retrieval behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)