摘要:

AbstractRats reared from weaning in a complex environment with other rats and numerous objects display sex differences in several brain areas, yet there is little systematic information on the types of interactions that rats have within complex environments or whether there are sex differences in these interactions. Therefore, male and female rats were observed in the complex environment over a 15–30‐day period in three separate replications that included same‐sex and mixed sex groups of rats. The rats spent considerably more time interacting with the objects than in social interactions in all replication, and the types of interactions varied little over the length of the study. A few sex differences appeared, such as in play fighting, but these differences were small and not consistent across replications. Male and female rats interacted with the environment in a very similar m

ISSN:0012-1630    

DOI:10.1002/dev.420190602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIn four experiments, different preparations and modes of prenatal administration of ACTH all failed to produce any substantial effects upon male sexual behavior in mice. In Experiment 1, CD‐1 females implanted during the third trimester of pregnancy with osmotic pumps releasing varied dosages of ACTH1−24produced male offspring with essentially normal copulatory behavior. In Experiment 2, prenatal injections of high doses of ACTH1−24had no effect upon male sexual activity. In Experiment 3, osmotic pumps releasing ACTH1−39during the third trimester of pregnancy had no effect upon sexual behavior of offspring. However, aggressive behavior was significantly reduced, relative to untreated controls, in offspring of all females implanted with pumps, including those releasing only saline. In Experiment 4, third‐trimester injections of ACTH1−39in long‐acting gel form had no effect on the sexual behavior or aggression of offspring of C57 strain females. In most of these experiments, ACTH treatment significantly reduced body weight. These results do not confirm previous suggestions that pituitary‐adrenal hormones influence the perinatal differentiation of sexually dim

ISSN:0012-1630    

DOI:10.1002/dev.420190603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe goal of this work was to determine the shortest period of exposure to environmental complexity (EC) that would produce measurable changes in brain weight or RNA content. This period varied with the age of subjects. In young adult rats, 3 months old, 4 days of exposure to EC increased the RNA concentration in the occipital cortex above the level of littermates kept in impoverished condition (IC). Cortical weight was not affected. Seven or one daily hrs of exposure to EC did not produce significant differences between rats in EC and IC. In periadolescent rats, 30‐ to 40‐day‐old, 1 daily hr of enrichment for 4 days increased both the weight of occipital cortex and its RNA content. Exposures of 7 or 24 hrs/day produced similar results. In another experiment with periadolescent rats 1 hr or even 10 min of exposure to EC per day, for 4 days, increased total cortical weight and RNA content. Thus, periadolescent rat brain display remarkably high plasticity. These very short exposure periods are comparable to the duration of learning sessions in simple formal trai

ISSN:0012-1630    

DOI:10.1002/dev.420190604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractDevelopmental effects of a single hydrocortisone (HC) injection (80 μg/g on day 2 postnatal) were compared in two closely related species, meadow voles (Microtus pennsylvanicus) and pine voles (M. pinetorum). Effects of hormone administration were assessed in terms of the development of swimming behavior (head/nose position and front paw movement), alterations in social interactions (spatial location with respect to a stimulus animal), and by changes in somatic and brain growth. Although adult patterns of swimming behavior were found to be quantitatively different in meadow and pine voles, normal maturation in both species involved a progressive elevation of head/nose position along with a gradual inhibition of front paw movement. Compared with saline controls, HC‐treated meadow voles showed an accelerated attainment of their adult pattern, whereas hormone‐treated pine voles displayed a retardation in their swimming development. HC administration similarly led to increased body weights in developing meadow voles but decreased body weights in young pine voles. There was a tendency for hormone‐treated meadow voles to spend more time near a stimulus animal than their control counterparts, whereas the opposite was observed for pine voles. In both species, the HC group displayed decreased cerebral and cerebellar weights in adulthood, whereas other organs were generally unaffected by hormone administration. Neurochemical analyses revealed no treatment effects or treatment by species interactions with respect to cerebral DNA levels. On the other hand, treated meadow voles but not pine voles showed an elevated concentration of sulfatide, a myelin‐related lipid. These results are the first to demonstrate divergent behavioral and neurochemical effects of early glucocorticoid administration in closely related species studied under the same conditions. Furthermore, in accordance with earlier experiments on rats, swimming behavior was shown to be a useful measure for assessing changes in neuromuscular ma

ISSN:0012-1630    

DOI:10.1002/dev.420190605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractNewborn female Long‐Evans rats were divided into groups of normal, hypothyroid [0.1% propylthiouracil (PTU) a reversible antithyroid goitrogen in the litter's drinking water], and hypothyroid rehabilitated (PTU water from birth to day 25, normal water thereafter). The rats were tested for several adaptive behavioral tasks between 40 and 90 days of age. At day 50, serum concentration of TSH and thyroid hormones revealed no detectable amounts of T4 and a 10‐fold increase in TSH in the hypothyroid rats. At the same age in the rehabilitated animals, TSH levels were still below normal, a deficit fully normalized by day 90. Normal 50‐day‐old rats responded to pain stress (electric footshocks) by a significant depression of serum T4 and elevation of T3 levels within 10 min of treatment, whereas the rehabilitated animals exhibited an opposite pattern of response, i.e., an increase in the circulating T4 and a decrease in T3. At 50 days of age, both hypothyroid and rehabilitated rats showed decreased exploratory activity and no habituation in the hole‐board test, whereas the locomotor activity of the rehabilitated females was significantly higher than that of the normals. No differences were found in the scores of passive avoidance learning (one trial step‐through) among the three groups. Similarly, the rate of acquisition of the active one‐way conditioned avoidance response (CAR) of the hypothyroid and rehabilitated rats did not differ significantly from that of the controls. However, the hypothyroid rats required significantly more unconditioned stimuli (footshocks) to acquire CAR and showed longer response latency and less intertrial responses. Although the hypothyroid rats showed no extinction of CAR, the rehabilitated rats were capable of extinction to an extent indistinguishable from normal rats. But compared with the normal animals, the rehabilitated rats showed significantly higher intertrial activity during both the acquisition and extinction

ISSN:0012-1630    

DOI:10.1002/dev.420190606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractUnder natural conditions, if maternal imprinting is to occur it must occur in a social situation which includes the presence of broodmates. In the laboratory it has been shown that social rearing with siblingspriorto maternal imprinting interferes with the establishment of maternal imprinting, whereas social experience with siblingsaftermaternal imprinting enhances the imprinting experience. The present study examined the influence of social experience with broodmatesduringan imprinting trial on the establishment of a visually imprinted maternal preference in domestic mallard ducklings (Anas platyrhynchos). Twenty‐four‐hour‐old ducklings were allowed to follow a stuffed mallard hen for 30 min either individually or in a brood of four same‐aged ducklings. The birds trained alone subsequently showed an imprinted preference for the familiar mallard hen over an unfamiliar pintail hen or four stuffed ducklings in simultaneous choice tests at 48 and 72 hr after hatching. Ducklings trained with broodmates did not show a preference for the familiar mallard hen over the unfamiliar pintail hen and displayed a preference for the stuffed ducklings over the mallard hen at 48 and 72 hr choice tests. These results demonstrate that even brief (30 min) experience with siblings during a maternal imprinting trial results in peer imprinting that interferes with the establishment of maternal imprinting. These and other results of a similar sort render dubious the significance of most laboratory studies of imprinting for an understanding of such events in

ISSN:0012-1630    

DOI:10.1002/dev.420190607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractWe studied behavioral development in 12 mother‐reared social‐group‐living bonnet macaque (M. radiata) monkey infants during the first four months of life. Physiological data was subsequently recorded from a subset of six using implantable biotelemetry. We compared these data to similar data previously collected in the same manner from similar age social group living pigtail macaque (M. nemestrina) infants. Bonnet infants were more active and apart from mother more throughout development. While in physical contact with mother, however, they were more likely to be enclosed if they were bonnets, but only in proximity or passively supported if they were pigtails. Bonnets also had more social contact with other adults.Mean day and night heart rate and body temperature, heart rate and body temperature circadian rhythms, and most nocturnal sleep variables were virtually identical in bonnets and pigtail infants. These findings suggest that developmental differences in social behavior in two closely related species of macaque monkey need not be accompanied by differences in physiological patt

ISSN:0012-1630    

DOI:10.1002/dev.420190608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the effect of presence of siblings and exposure to colony cues during early life on the onset of maternal behavior at 20 and 75 days of life, and on subsequent emotional behavior in juvenile and adult female rats. Different groups of animals were reared either (1) with a large number or a small number of siblings (sibling factor), or (2) in the colony room or in a room apart from other mothers with pups (colony factor). Animals were tested for latency (in days) to show maternal behavior at either 20 or 75 days of age, and for emotional behavior (using the open field apparatus) at either 20–40 or 80–100 days of age. Exposure to colony sensory cues significantly reduced latencies for pup retrieval and nestbuilding in adults, but not in juveniles. Exposure to a large number of siblings reduced the latencies, in both adults and juveniles, to nest build; in juveniles, to lie over 75% of the litter; and in adults, to adopt a nursing posture. Consistent with prior research, juveniles had longer latencies than adults for a number of pup‐directed behaviors including: latency to become maternal, latency to retrieve pups, latency to adopt a lactating posture, latency to lick/genital lick, and latency to nest‐build. In the emotionality tests, the young animals scored as less emotional than the adults, an effect which was further exaggerated by early colony exposure. Overall results indicated that manipulation of early rearing environments does have a significant positive effect on later responses to young pups by both juvenile and adult fema

ISSN:0012-1630    

DOI:10.1002/dev.420190609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractInfant rats from 1 to 15 days of age received oral infusions of various taste solutions, and their intake of and behavioral responses to the infusions were observed. From 1 day of age on, pups responded to strong acid and quinine solutions with certain characteristic aversive responses and suppressed intake (Experiment 1). Although even very young (1‐ and 3‐day‐old) pups suppressed their intake of strong quinine and acid solutions, and rejected them by showing certain aversive responses (gaping and forelimb flailing), other components of the adultlike aversion response sequence (chin scraping and paw treading) did not appear until approximately 12 days of age. This suggests that the failure of pups to engage in chin scraping and paw treading prior to 12 days is not due to an inability to detect aversive solutions, but rather may be due to an immaturity in pups younger than 12 days of the neural substrates subserving these aversive responses. The emergence of chin scraping and paw treading to strong acid or quinine solutions was not influenced to any marked extent by either the deprivational state of the pup (Experiment 2a) or the site of the infusion (Experimen

ISSN:0012-1630    

DOI:10.1002/dev.420190610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractJapanese quail chicks were exposed for 2.5 hrs to either a white or a normal stuffed adult conspecific (= model). During this period the model was either nonmoving or it moved for short periods. This movement could be contingent or noncontingent upon distress calls of the chicks. In each condition, exposure led to a significant preference for the familiar model over the nonfamiliar one during a 10‐min choice test. Chicks exposed to a nonmoving model had the weakest preference for the familiar model, whereas this preference was strongest in chicks exposed to the contingent moving model; the preference of the chicks exposed to the noncontingent moving model was in between. The results indicate that the extend to which stimulus movement enhances filial imprinting depends on the relation between the chicks behavior and the timing of the stimulus movement. However, it is not clear yet whether the effect arose because the chicks perceived the contingency between the stimulus movement and their behavior or by another mechanis

ISSN:0012-1630    

DOI:10.1002/dev.420190611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY