Long-term retention of spatial navigation by preweanling rats

The present study was designed to examine retention of spatial information in the immature, Fischer-344N rat using a savings paradigm. Following training to locate a hidden platform using extramaze cues, preweanling animals (17 days of age) were immediately probed by testing in the tank with the platform removed. One week later, pups (26 days of age) were given an additional four training trials immediately followed by a second probe test to examine the animals' memory for the location of the platform. Animals that received initial training at 17 days of age demonstrated significant savings of information when tested after the retention interval. These data replicate our recent report of spatial navigation capabilities in the preweanling rat, and extend those findings by demonstrating that preweanling spatial navigation performance permits more rapid and accurate navigation following a 7-day retention interval after a "reinstatement" insufficient to produce accurate navigation in maturation controls.     

Prenatal exposure to temporal and spatial stimulus properties affects postnatal responsiveness to spatial contiguity in bobwhite quail chicks

Little is known about how experiential factors guide and organize the development of intersensory perception. This study manipulated the amount of late prenatal and early postnatal experience with the temporal synchrony and spatial contiguity of audio-visual stimulation available to bobwhite quail embryos and hatchlings to explore this question. Results revealed that only embryos exposed to temporally synchronous and spatially contiguous audio-visual stimulation prior to hatching subsequently preferred spatially contiguous audio-visual maternal information following hatching, despite being denied postnatal visual experience. In contrast, embryos that did not receive exposure to both temporal synchrony and spatial contiguity (and were also denied postnatal visual experience) failed to show a preference for the spatial contiguity of maternal auditory and visual information following hatching. These results suggest that prenatal exposure to the amodal properties of temporal synchrony and spatial contiguity facilitate chicks' emerging sensitivity to the spatial contiguity of audio-visual information in the period following hatching.     

丰富环境干预对孕期手机辐射暴露后仔鼠认知功能的影响

目的:探讨丰富环境干预对孕期长时间手机辐射暴露后仔鼠认知功能的影响。方法:18只SPF级SD孕鼠随机分为两组,分别给予对照处理(不辐射)、长时间手机辐射处理(辐射24 h/d,21d),待仔鼠出生后饲养至18月龄,进行丰富环境干预,共分为3组,分别为对照组(CON)、手机辐射组(PR)及丰富环境组(PR+EE)。于丰富环境干预28 d后应用Morris水迷宫评定仔鼠认知功能;免疫组化及Western Blot检测海马区突触素(SYN)和脑源性神经营养因子(BDNF)表达;透射电镜观察海马区突触的超微结构。结果:与CON组相比,PR组及PR+EE组仔鼠的逃避潜伏期延长,跨越平台的次数减少,SYN和BDNF表达均减少,海马CA1区超微结构改变;而与PR组相比,PR+EE组逃避潜伏期缩短,穿越平台次数增加,SYN和BDNF表达均上调,且SYN阳性细胞增多,海马CA1区突触超微结构改变。结论:丰富环境干预可能通过上调海马SYN和BDNF表达,改变突触超微结构,提高突触可塑性,进而改善孕期手机辐射暴露后仔鼠的认知功能。     

Comparison of the effects of early handling and early deprivation on maternal care in the rat

It has been reported in the rat that postnatal manipulations can induce robust and persistent effects on offspring neurobiology and behavior, mediated in part via effects on maternal care. There have, however, been few studies of the effects of postnatal manipulations on maternal care. Here, we describe and compare the effects on maternal behavior on postnatal days 1-12 of two manipulations, early handling (EH, 15-min isolation per day) and early deprivation (ED, 4-hr isolation per day), relative to our normal postnatal husbandry procedure. Maternal behavior was measured at five time points across the dark phase of the reversed L:D cycle. EH yielded an increase in arched-back nursing across several time points but did not affect any other behavior. ED stimulated a bout of maternal behavior such that licking and arched-back nursing were increased at the time of dam-litter reunion, although not at any other time point. Neither EH nor ED affected weaning weight significantly. Importantly, within-treatment variation was high relative to these between-treatment effects.     

Prenatal cocaine and other substance exposure: effects on infant autonomic regulation at 7 months of age

This study examined the association between prenatal exposure to cocaine and autonomic regulation at 7 months of age. Heart rate (HR) and respiratory sinus arrhythmia (RSA) were obtained from 154 (79 exposed, and 75 nonexposed) infants during baseline and tasks designed to elicit positive and negative affect. Cocaine-exposed infants had higher HR during the positive affect task. There was a significant suppression of RSA during the negative affect task for nonexposed infants but not for exposed infants. Fetal growth and maternal caregiving behavior did not mediate or moderate this association. These results provide additional support for an association between prenatal cocaine exposure and dysregulation during infancy.     

The development of spatial capacity in piloting and dead reckoning by infant rats: use of the huddle as a home base for spatial navigation

Two forms of spatial navigation, piloting using external cues and dead reckoning using self-movement cues, are manifest in the outward and homeward trips of adult rats exploring from a home base. Here, the development of these two forms of spatial behavior are described for rats aged 14-65 days using a new paradigm in which a huddle of pups or an artificial huddle, a small heat pad, served as a home base on an open circular table that the rats could explore. When moving away from both home bases, the travel distance, path complexity, and number of stops of outward trips from the home base increased progressively with age from postnatal day 16 through 22. When returning to the home bases, the return trips to the home base were always more direct and had high travel velocities even though travel distance increased with age for the longest trips. The results are discussed in relation to the ideas that: (1) the pups pilot on the outward portion of their excursion and dead reckon on the homeward portion of their excursion, and (2) the two forms of navigation and associated spatial capacity are interdependent and develop in parallel and in close association with locomotor skill.     

Prenatal exposure to tobacco and marijuana and child autonomic regulation and reactivity: An analysis of indirect pathways via maternal psychopathology and parenting

We examined a conceptual model for the associations of prenatal exposure to tobacco (PTE) and marijuana with child reactivity/regulation at 16 months of age. We hypothesized that PTE would be associated with autonomic reactivity and regulation that these associations would be indirect via maternal anger/hostility, depression/stress, or harsh parenting assessed at 2 months and that these effects would be most pronounced among children exposed to both tobacco and marijuana (PTME). Participants were 247 dyads (81 PTE, 97 PTME, and 69 nonexposed) who were followed up at 2 (N = 247) and 16 months (N = 238) of child age. Results from model testing indicated an indirect association between PTME and autonomic functioning during the second year of life, which was mediated by harsh parenting during caregiver–infant interactions. This study fills an important gap in the literature on PTE, PTME, and autonomic regulation during the toddler years, highlighting the role of maternal parenting as important intervening variables.     

Prenatal ethanol exposure attenuates GABAergic inhibition in basolateral amygdala leading to neuronal hyperexcitability and anxiety-like behavior of adult rat offspring

Prenatal exposure to a relatively high-dose ethanol (EtOH) caused anxiety-like behavior of adult male rat offspring. Previous studies have demonstrated that GABA system in the basolateral amygdala complex (BLA) is involved in the pathogensis of anxiety-related disorders. The role of GABAergic system in the BLA was investigated in anxiety-like behavior evoked by prenatal EtOH exposure. The infusion of midazolam (MDZ), a positive modulator of GABA_A receptor, into the BLA prevented anxiety-like behavior in EtOH-offspring without affecting the corresponding behavior of control offspring. The data suggest that anxiety-like behavior could be causally related to increased neuronal excitability attributable to depressed GABAergic inhibition in the BLA. To test this hypothesis, evoked potential was studied using brain slices from EtOH-offspring. Potential evoked in the BLA by single stimuli applied to external capsule showed multispike responses, indicative of GABAergic disinhibition. These multiple responses were no longer evident after the perfusion with MDZ. In the slices from EtOH-offspring, paired-pulse inhibition (GABA_A-dependent) was suppressed. Also, in EtOH-offspring, long-term potentiation (LTP) was induced by a single train of high frequency stimulation, which did not induce LTP in control rats. Moreover, MDZ pretreatment prevented the facilitating effect of EtOH on LTP induction. The data provide the functional evidence that prenatal EtOH exposure attenuates GABAergic inhibition in the BLA resulting in neuronal hyperexcitability and anxiety-like behavior of adult rat offspring.     

Prenatal cocaine exposure and children's language functioning at 6 and 9.5 years: moderating effects of child age, birthweight, and gender

OBJECTIVE: To evaluate whether prenatal cocaine exposure (PCE), or the interaction between PCE and contextual variables, is associated with children's language at age 6 and 9.5 years, adjusting for relevant covariates. METHODS: Analyses were based on 160 low-income, urban children from a prospective study who completed a standardized language assessment at 6 and 9.5 years. PCE was determined using neonatal meconium assays and maternal self-report. RESULTS: Significant interaction effects of PCE on language outcomes were found in multivariate longitudinal analyses using generalized estimating equations (GEE). Children with PCE had lower receptive language than unexposed children at 6 but not at 9.5 years, lower expressive language if they had lower birthweight, and lower expressive and total language if they were female. Other risk (e.g., violence exposure) and protective factors (e.g., preschool experience) were related to language outcomes regardless of PCE status. CONCLUSIONS: Age, birthweight, and gender moderated the relation between PCE and school-aged children's language.     

Comparison of developmental trajectories for place and cued navigation in the Morris water task

Previous studies investigating the development of place and cued learning using the Morris water task are in disagreement regarding the day in development that each type of learning emerges. Here, place and cued navigation in the water task were examined in differently aged groups of young male and female rats (P17, P18, P19, P20, and P24) during a single day of training. When only distal cues were present, P20 and P24 but not younger rats learned the location of the hidden platform. In contrast, when a proximal cue marked the platform location, rats as young as P17 showed evidence of cue-controlled navigation, although only P18 and older rats exhibited cued learning. In line with most previous studies, these results indicate that cued learning emerges earlier in development than place learning and support a dissociation of developmental trajectories for the neural systems underlying the two types of navigation.     

Synergistic effects of the MTHFR C677T polymorphism and hypertension on spatial navigation

Navigation skills deteriorate with age, but the mechanisms of the decline are poorly understood. Part of the decrement may be due to age-related vascular risk factors. The T allele in a C677T variant in methylenetetrahydrofolate reductase (MTHFR) gene is associated with elevated plasma homocysteine, which is detrimental to vascular integrity and has been linked to cognitive decline. We inquired if a combination of physiological (hypertension) and genetic (MTHFR 677T) vascular risks has a synergistic negative impact on cognitive performance in otherwise healthy adults. We tested 160 participants (18–80 years old) on a virtual water maze. Advanced age, female sex, and hypertension were associated with poorer performance. However, hypertensive carriers of the T allele performed significantly worse than the rest of the participants at all ages. These findings indicate that hypertension combined with a genetic vascular risk factor may significantly increase risk for cognitive impairment.     

Differences between two psychogenetically selected lines of rats in a swimming pool matching-to-place task: long-term effects of infantile stimulation

The present study explored the effects of infantile stimulation (i.e., neonatal handling or NH) on the performance of 18-month-old Roman high-avoidance (RHA/Verh) and low-avoidance (RLA/Verh) rats in a swimming pool matching-to-place (SPMP) test. This test (also called repeated acquisition and place learning-set paradigm) consists of administering pairs of consecutive trials in the Morris water maze. The difference between each odd and the consecutive even trial of a trial pair is considered to be a measure of working memory. The same rats were first tested for exploration and novelty-seeking in a hole-board test in the presence of novel objects, which showed that RHA/Verh rats were more explorative than their RLA/Verh counterparts, and that NH treatment augmented exploration in RLA/Verh rats, generally eliminating the genetically-based differences between the lines. RHA/Verh rats performed less efficiently than RLA/Verh rats in the SPMP test, and NH facilitated acquisition in the early stages of training in both rat lines, an effect that was presumably due to an improvement in the acquisition of spatial reference information. Performance during training also indicated that RHA/Verh rats showed less differentiated behavior between odd and even trials, indicating a relative working memory deficit at advanced ages in that rat line.     

Sexually dimorphic effects of postnatal treatment on the development of activity‐based anorexia in adolescent and adult rats

Hyperactivity of the hypothalamic–pituitary–adrenal (HPA) axis is a marked feature of anorexia nervosa. Using a modified version of the activity‐based animal model of anorexia nervosa, we examine whether factors known to affect HPA axis activity influence the development of activity‐based anorexia (ABA). Male and female rats were subjected to maternal separation or handling procedures during the first two postnatal weeks and tested in a mild version of the ABA paradigm, comprised of 2‐hr daily running wheel access followed by 1‐hr food access, either in adolescence or adulthood. Compared to handled females, maternally separated females demonstrated greater increases in wheel running and a more pronounced running‐induced suppression of food intake during adolescence, but not in adulthood. In contrast, it was only in adulthood that wheel running produced more prolonged anorexic effects in maternally separated than in handled males. These findings highlight the interplay between early postnatal treatment, sex of the animal, and developmental age on running, food intake, and rate of body weight loss in a mild version of the ABA paradigm. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 679–695, 2009.     

Proximal versus distal cue utilization in preweanling spatial localization: the influence of cue number and location

The present study was designed to examine the role of cue location and number in spatial navigation of the preweanling Fischer-344N rat in the Morris water maze using a protocol consistent with the pups' response repertoire. The proximal (visible platform) versus distal (hidden platform) cue strategy was used, and spatial cues within the extramaze environment were configured such that the arrangement presented either a double cue or null cull condition relative to the platform location. All pups' performance improved with training; however, probe trial performance, defined by quadrant time and platform crossings, revealed distal-double cue pups demonstrated spatial navigational ability superior to the remaining groups. This experimental dissociation suggests that a pup's ability to spatially navigate a hidden platform is dependent on not only its response repertoire and task parameters but also its visual acuity, as determined by the number of extramaze cues and the location of these cues within the testing environment. The hidden versus visible platform dissociation may not be a satisfactory strategy for the control of potential sensorimotor deficits.