Social-seeking and novelty-seeking behavior as a function of differential rearing histories.

Rats were handled daily from birth until weaning or were nonhandled controls. At weaning Ss were reared with littermates or in isolation. At 90 days some of the socially reared Ss were placed into isolation. Total N = 44 males, 1 from each of 44 different litters. At 100 days S was placed for 10 min. into the stem of a T shaped unit. S could remain where it was, enter a social chamber, or enter a novel chamber. Time in each chamber, activity, and defecation were recorded for 4 successive days. Handled Ss were significantly more active, and spent significantly more time in the social and novel chambers than nonhandled controls. Ss reared in a social environment until testing spent significantly less time in the novel chamber than Ss undergoing long-term or short-term social isolation. The handling variable was found to interact significantly with postweaning rearing and test days. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparisons of behavioral effects of hippocampal and prefrontal cortex lesions in the rat.

5 groups of 5 male Wistar rats each, with aspiration lesions of dorsomedial frontal cortex, ventrolateral frontal cortex, hippocampus, or posterior cortex, or with sham operations, were tested in 5 behavioral situations: emotionality assessment, serial spatial reversals, 70:30 spatial probability, differential reinforcement of low rates (DRL), and barpress extinction. Ss with posterocortical lesions did not differ from operated controls on any task. The effects of lesions in the 2 anatomically defined frontal subfields were clearly dissociated on spatial reversals, spatial probability, and DRL. Lesions in either subfield produced a significant increase in emotionality relative to controls, and neither lesion affected barpress extinction. Results suggest that both frontal subfields may be functionally related to the hippocampus but in different ways. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal frontal lesions in the rat: Sparing of learned but not species-typical behavior in the presence of reduced brain weight and cortical thickness.

Used 70 Long-Evans rats to compare Ss that underwent complete removal of the cortex anterior to bregma in adulthood (frontal cortex) with Ss who had similar removals at 7 or 25 days of age. Excision of the frontal cortex in adult Ss produced transient aphagia, chronic motor abnormalities in feeding, a chronic drop in body weight, increased activity in running wheels, impaired performance on a spatial reversal learning task, and chronic abnormalities in a variety of species-typical behaviors. Lesions in infants failed to produce aphagia, a chronic drop in body weight, increased activity, or impaired learning of a spatial reversal task. However, infant lesions did not allow sparing of complex species-typical behaviors. In comparison with controls and Ss operated on in adulthood, cerebral hemispheres of neonatal operates were smaller both in surface dimensions and weight, the thalamus was smaller, and the cerebral cortex was thinner. Data imply that there may be substantially less sparing of function following frontal cortex lesions in infancy than previously believed and that neonatal frontal lesions in rats have significant effects on brain development in regions far removed from the actual site of surgical excision. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of repeated testing on sexual behavior of the female rat.

Investigated effects of stimulation during repeated testing, using 24 female Sprague-Dawley rats in which intromission was prevented by a vaginal mask. Ss were ovariectomized and administered 1 mg of estradiol benzoate (EB) daily for 10 days (Exp I) or 5 mg of EB for 2 days (Exp II). Behavioral indices included lordosis quotient (a measure of sexual receptivity) and rejection quotient (a measure of social rejection of the male). Intensity and duration of lordosis gave additional measures. In Exp I hourly testing increased lordosis quotient and duration, especially in Ss receiving EB for 5 days; no effects of daily testing were shown. Exp II compared the behavior of Ss that were either handled hourly and tested hourly with the male rat or only handled hourly to the behavior of Ss that were tested and handled only once. Repeated testing and/or handling facilitated sexual responsiveness, while Ss that received neither treatment were sluggish in their social response to the male rat when they were tested, and were not sexually receptive. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of species-typical behavior in the Syrian golden hamster.

The behavior of a total of 84 Syrian golden hamsters with lesions to the medial frontal cortex (MF), orbital frontal cortex (OF), cingulate cortex (CING), posterior cortex (POST), hippocampus (HPC), septum (SEPT), or amygdala (AMYG) was compared with that of 12 control hamsters in a variety of situations, including weight regulation, food hoarding, nest building, neophobia, bait shyness, sex preference, territorial aggression, and shock-induced aggression. The behavior of Ss with OF or AMYG lesions was doubly dissociable from the behavior of Ss with MF, HPC, or SEPT lesions. The OF and AMYG lesions produced severe weight losses, and all OF Ss were aphagic and adipsic and subsequently died. The HPC, MF, and SEPT lesions severely disrupted hoarding and nest building, whereas the other lesions affected neither. None of the lesions impaired the development of bait shyness when a sucrose solution was paired with sickness, but both AMYG and SEPT lesions may have produced a mild impairment when an NaCl solution was paired with sickness. Only amygdala lesions produced consistent behavioral changes on the social tests. Neither cingulate nor posterior cortical lesions significantly altered behavior on any of the tests. Results support the idea that different forebrain regions can be functionally dissociated by using behavioral tests that are biologically significant. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social stimulation of reproductive development in male deer mice housed on a short-day photoperiod.

Male deer mice (Peromyscus maniculatus), born of mothers housed on a long-day (LD) photoperiod (15:9 hrs light/dark), were either switched to a short-day (SD) photoperiod (6:18 hrs) at birth or continued on their prenatal LD photoperiod. From weaning until 6 wks of age, Ss were housed with an adult female or in social isolation. Ss reared on an SD photoperiod had smaller testes, seminal vesicles, and ventral sebaceous glands that did those reared on LD. Postweaning exposure of SD Ss to females stimulated reproductive organ growth as measured at 6 wks of age. Results indicate that both photic and social stimuli regulate reproductive development in male deer mice and that positive social cues can stimulate maturation even in the presence of negative photic cues. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal handling alters brain organization but does not influence recovery from perinatal cortical injury.

Handling rat pups by removing them from the nest during the preweaning period has been shown to influence brain and behavioral development. The authors hypothesized that handling rats with perinatal (Day 4) medial frontal cortex removals might attenuate behavioral deficits and reverse dendritic atrophy associated with such an injury. On the day after surgery, pups were removed from the nest for 15 min, 3 times per day until weaning. Animals were tested as adults in the Morris water task and on skilled reaching. Handled animals showed no improvement in behavioral performance. The handling procedure led to a decrease in dendritic length in parietal cortex, but spine density was unchanged. No therapeutic advantage was observed following the preweaning handling of brain-injured rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical cholinergic impairment and behavioral deficits produced by kainic acid lesions of rat magnocellular basal forebrain.

The rat magnocellular basal forebrain (MNBF) is homologous to the human nucleus basalis of Meynert, a structure implicated in the cholinergic hypothesis of cognitive impairment in Alzheimer's disease (AD). In the present study, 18 male Sprague-Dawley rats with kainic acid lesions in the MNBF were compared with 6 unoperated controls, 10 sham-operated controls, and 6 controls injected with kainic acid in the cortical area directly above the MNBF. MNBF lesions depleted choline acetyltransferase in cortex but not in striatum or hippocampus. Cortical dopamine levels were unchanged; serotonin levels were unchanged in hippocampus and parietal cortex but decreased in frontal cortex. Compared with controls, MNBF-lesioned Ss were impaired in 24-hr retention, but not acquisition, of a passive avoidance task with escapable footshock. The groups did not differ in mean number of daily avoidances on a barpress active avoidance task, although learning was slower in MNBF-lesioned Ss. In a serial spatial discrimination reversal test, MNBF-lesioned Ss performed significantly worse than controls. This model may be useful for studying the role of the cholinergic system in memory and possibly for developing treatment strategies to alleviate the cognitive dysfunction of AD. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sparing of function after infant lesions of selected limbic structures in the rat.

The effects, in adult Ss, of limbic lesions produced in infancy were studied in 273 male Wistar rats using weight gain and conditioned emotional response (CER) and condtitioned avodiance response (CAR) acquisition as the critical measures. Ss received bilateral lesions of the amygdala, septum, postventral hippocampus (PH) anterodorsal hippocampus (AH), or frontal cortex either as infants (at 10 days of age) or as adults (at 60 days). Normal and anesthetized control groups were also used. Frontal cortical lesions, AH lesions, and anesthetization had no effect on weights or on CER and CAR acquisition. Both infant and adult amygdala and septal lesions significantly disrupted normal weight gain. Adult-accrued amygdala and PH lesions significantly retarded CER acquisition, and adult septal and PH lesions significantly facilitated CAR acquisition. Infant-accrued amygdala lesions significantly facilitated CAR acquisition, and infant PH lesions had no effect on either task. Results are interpreted to mean that the observed task-specific recovery in early-operated Ss may have been due to some form of functional reorganization. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organizational changes in cholinergic activity and enhanced visuospatial memory as a function of choline administered prenatally or postnatally or both.

This experiment was an examination of the effects of supplemental dietary choline chloride given prenatally (to the diet of pregnant rats) and postnatally (intubed directly into the stomachs of rat pups) on memory function and neurochemical measures of brain cholinergic activity of male albino rats when they became adults. The data demonstrate that perinatal choline supplementation causes (a) long-term facilitative effects on working and reference memory components of a 12-arm radial maze task, and (b) alternations of muscarinic receptor density as indexed by [–3H]quinuclidinyl benzilate (QNB) binding and choline acetyltransferase (ChAT) levels in the hippocampus and frontal cortex of adult rats. An analysis of the relationship between these organizational changes in brain and memory function indicated that the ChAT-to-QNB ratio in the hippocampus is highly correlated with working memory errors, and this ratio in the frontal cortex is highly correlated with reference memory errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preoperative differential housing and dorsal hippocampal lesions in rats.

The resemblance between the effects of social isolation and of hippocampal lesions (HCLs) in rats led to a study that investigated whether rats socially isolated at weaning rather than grouped counterparts show less behavioral change after sustaining dorsal HCLs when adults. Ss were 8 grouped male Lister rats with HCLs, 8 grouped male controls, 8 isolated male with HCLs, and 8 isolated controls. In socially reared Ss, HCLs produced increased ambulation and object contact in an open field, reduced passive avoidance in a runway task, and produced faster acquisition of active avoidance in a shuttlebox, but there were no such differences in isolation-reared Ss. Ambulation and object contact in isolates were intermediate to those of HCL Ss and intact group-housed Ss, and the behavior of isolates during passive and active avoidance training was generally similar to that of grouped Ss with HCLs. The introduction of a distractor during approach training in an alley reduced running speeds more in Ss with HCLs than in controls. The significant interactions between housing and lesion state suggest that neural pathways associated with the hippocampal formation may mediate some behavioral effects of differential housing. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychological disturbance in fibromyalgia: relation to pain severity

On day 2 after delivery, dams of the DBA/1 mouse inbred strain (n = 20/group) with their litter were allocated to one of the following groups: NH21, nonhandling, housed 1 litter/cage, weaned on postnatal day (PND) 21;H21, handling, housed 1 litter/cage, weaned on PND 21; NH30, nonhandling, group-housed (5 litters/cage), weaned on PND 30; H30, handling, group-housed (5 litters/cage), weaned on PND 30. Two male pups of each litter were color marked on PND 2. From PND 8-21 they were removed from their cage, gently held in the experimenter's hand for 5 min/day. The two marked males of each litter were housed together after weaning, and tested in the open-field on PNDs 51-53, and one of each of these siblings was tested for hot-plate latencies on PND 54. Being raised in group-housing and weaned on PND 30 resulted in offspring exhibiting shorter latencies to initiate behavior and higher percentages of centerfield entries in the open field, hot-plate latencies, however, remained unaffected. Preweaning handling increased hot-plate latencies and the number of grooming episodes in the open field, and it decreased defecation, percent centerfield entries and open-field activity in general. It is concluded that the two forms of early experience have different effects on neurobehavioral endpoints 8 weeks after birth.     

Region-specific serotonin1A receptor turnover following irreversible blockade with EEDQ

The neurotoxicant N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) irreversibly inactivates serotonin1A (5-HT1A) receptors and is a useful tool to investigate the kinetics of receptor recovery following administration of the drug. Recovery characteristics were determined for 5-HT1A receptors located in the frontal cortex and hippocampus of male Sprague-Dawley rats treated with EEDQ (6.0 mgth kg-1, s.c.) or vehicle. Saturation binding assays using [3H]8-OH-DPAT were conducted, using frontal cortex and hippocampal membrane homogenates, at several time points following EEDQ treatment (1, 2, and 8 days post-injection). Scatchard analyses revealed region-specific differences in the recovery of these receptors. 5-HT1A receptors in the hippocampus degraded more quickly but recovered faster than those in the frontal cortex; receptor half-life was also shorter in the hippocampus than in frontal cortex. These regional variations are discussed in terms of differential receptor synthesis. The pathophysiological relevance of these findings to aging and disorders involving 5-HT1A receptor dysfunction, including depression and anxiety, is discussed.     

Time-dependent changes in amphetamine self-administration following frontal cortex ablations in rats.

Conducted 2 experiments with a total of 28 operated, 25 sham-operated, and 21 normal female Sprague-Dawley albino rats. Ss were trained to intravenously self-administer dextroamphetamine (.01 mg/kg per reward infusion) during daily 1-hr testing sessions. Following removal of frontal cortex, rates of dextroamphetamine self-administration were higher at early (3-5 days) postoperative intervals but lower at later (2-4 wks) postoperative intervals. These and other results indicate that, as a function of time after surgery, frontal Ss were first hyposensitive and then became increasingly hypersensitive to the rewarding effect of dextroamphetamine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Compared 15 rats with lesions of the medial frontal, orbital frontal, or parietal cortex with 5 rats with complete removal of the neocortex and 5 normal controls on 3 spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all 3 tasks. Ss with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, Ss with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were poor at learning the water task. Ss with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate Ss. Results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital frontal cortex play a dissociable role in the control of spatial orientation. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early experience in domestication.

Conducted 2 experiments to assess the ontogenetic as well as phylogenetic influences of early experience on domestication. A total of 40 Long-Evans hooded and 32 Sprague-Dawley albino domestic rats and 72 1st generation, laboratory-reared wild rats were the Ss. Exp I was a factorial, reciprocal cross-foster study. Exp II was a factorial assessment of the combined effects of preweaning handling and postweaning enriched environments. These experiments on rat domestication show that preweaning handling had a strong influence on the ontogenetic development of the S in terms of reduced emotionality. Handled wild Ss became much more like domestic Ss in their behavior. This finding for handling contrasted with minimal effects for cross-fostering and enriched environments. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of the contributions of the prefrontal, motor, and parietal cortex of the control of movement in the rat: An experimental review.

Studied 48 male Long-Evans rats with or without lesions of the motor, medial frontal, or posterior parietal cortex or all the neocortex (decorticate) on a battery of tests. The tests assessed sensorimotor behavior, postural reflexes, feeding behavior, tongue extension, grooming, beam walking, response to the puzzle latch box, swimming, and food hoarding. Removal of the motor cortex produced abnormalities in postural reflexes and in behaviors requiring fine movements of the distal effectors. In contrast, removal of the medial frontal, orbital frontal, or posterior parietal cortex produced chronic impairments in specific behavioral patterns, depending on the precise region that was removed: Ss with medial frontal lesion were impaired at the use of the forepaws; Ss with orbital frontal lesions were impaired at making fine movements of the tongue and snout; and Ss with posterior parietal lesions were impaired at placement of the limbs in space. Complete removal of the neocortex produced abnormalities in every behavior. The possibility of deriving models of cortical function of primates from the rat is discussed. (French abstract) (66 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of postweaning social experience on response of Siberian hamsters (Phodopus sungorus sungorus) toward young.

Between 18 and 50 days of age, 83 male and 66 female Siberian hamsters were housed either with (a) same-sex littermates; (b) opposite-sex littermates; (c) opposite-sex littermates and parents; or (d) opposite-sex littermates, parents, and a younger litter. When adults, Ss were presented with 2 3–8 day old pups for 8 hrs, and their responses were recorded. Rearing conditions did not affect behavior of females. Males housed with female littermates in the absence of a younger litter showed fewer pup attacks and more nesting with pups than did males housed only with other males. Thus, housing with females in the early postweaning period may influence males' adult responses toward pups. Only among Ss housed with same-sex littermates did males and females differ in their response to pups, a result emphasizing that sex differences in behavior may depend on early social rearing. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention and acquisition of classical trace conditioned responses by rabbits with hippocampal lesions.

Examined the effects of dorsal hippocampal lesions on retention of classical trace conditioned responses (CRs) using the rabbit nictitating membrane preparation. In Exp I, 18 New Zealand albino rabbits were trained to criteria and then lesioned either in the cortex or in the hippocampus and the cortex. Hippocampal damage had no effect on the retention of responses but produced significantly longer onset latencies. A control group of hippocampal Ss acquired CRs at least as quickly as the prelesion Ss and exhibited longer response onset latency. Exp II, with 24 Ss, evaluated the performance of hippocampal-lesioned Ss in classical trace conditioning with either a low-intensity periorbital shock or a corneal air puff as the unconditioned stimulus (UCS). Hippocampal Ss successfully acquired CRs under both conditions but exhibited an alteration of response onset that depended on the form of the UCS. Hippocampal Ss displayed shorter response onset in the air-puff condition and longer response onset in the shock condition. Cortical Ss consistently timed responses regardless of the UCS. Findings suggest that the hippocampus modulates temporal characteristics of learned behavior. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

3H]paroxetine binding is altered in the hippocampus but not the frontal cortex or caudate nucleus from subjects with schizophrenia

[3H]Paroxetine binding to particulate membrane from tissue, obtained at autopsy, from the hippocampus, frontal cortex, and caudate nucleus from subjects who had or had not had schizophrenia was measured. The density of [3H]paroxetine binding to membranes from subjects who had or had not had schizophrenia did not differ. Similarly, the affinity of [3H]paroxetine binding in the frontal cortex and caudate nucleus was not different. By contrast, the affinity of [3H]paroxetine binding to hippocampal membrane from subjects who had schizophrenia was significantly lower than the affinity of binding for the nonschizophrenic subjects (0.40 +/- 0.06 vs. 0.26 +/- 0.02; p < 0.05). As [3H]paroxetine binds to the serotonin transporter, these data suggest that the serotonin transporter is altered in the hippocampus in subjects with schizophrenia.