Performance Of Female Rats Research Articles

Non-specific Effect of Fear Conditioning and Specific Effect of Social Defeat on Social Recognition Memory Performance in Female Rats

The so called “emotion learning” literature describes the ability of distressing and aversive unconditioned stimuli to classically condition a learned avoidance response. In order to investigate the impact of experience with noxious stimuli in one conditioning context on learning and memory performance in a separate, non-aversively motivated task, juvenile recognition ability was examined in adult female rats exposed previously to one of two environmental stressors. In particular, experimental adult rats were either socially defeated by exposure to an aggressive conspecific rat or fear conditioned using single or multiple pairings with footshock prior to performance of the social recognition task. Experiment 1 established that repeated exposure to a single juvenile resulted in social memory formation reflected in decreased social investigation from the first to the second exposure. Experiment 2 documented that both single and multiple pairings of an environment with footshock produced robust freezing behavior (90–95% suppression of activity). In addition, fear conditioning produced a non-specific 5–60% increase in social investigation time in both single and multiple-pairing fear conditioned groups which confounded the ability of the social recognition measure to assess effects of fear conditioning on learning and memory performance per se. In contrast, Experiment 3 documented that when social recognition memory performance was impaired to 85% of control levels by imposition of a 2 h delay, exposure to a social defeat stressor reinstated optimal social recognition memory performance. These findings suggest that the after effects of fear conditioning include non-specific alteration of social investigation whereas exposure to conspecific aggression enhances subsequent social recognition memory.

Nicotine–antipsychotic drug interactions and attentional performance in female rats

Schizophrenia is marked by pronounced cognitive impairments in addition to the hallmark psychotic symptoms like hallucinations. Antipsychotic drugs can effectively reduce these hallucinations; however, the drugs have not resolved the cognitive impairment. Interestingly, nicotine, a drug commonly self-administered by people with schizophrenia, has been shown to significantly improve cognitive function of people with schizophrenia. The current study was conducted to determine the effect of typical (haloperidol) and atypical (clozapine and risperidone) antipsychotic drug treatment on sustained attention in rats performing a visual signal detection task. In addition, the interaction of haloperidol with chronic nicotine administration was assessed. Female Sprague–Dawley rats were injected subcutaneously with clozapine (0, 0.6, 1.25 and 2.5 mg/kg), risperidone (0, 0.025, 0.05 and 0.1 mg/kg) or haloperidol (0, 0.01, 0.02 and 0.04 mg/kg). In the second part of the study, the interaction of acute haloperidol (0, 0.005, 0.01 and 0.02 mg/kg) and chronic nicotine (5 mg/kg/day, for 4 weeks via osmotic minipump) was characterized. Clozapine, risperidone and haloperidol all caused dose-related impairments in percent hit performance. There was a significant linear dose-related impairment in percent hit caused by risperidone. All the doses of clozapine caused a significant impairment in percent hit at the higher luminance intensities in the visual signal detection task. The 0.01 and 0.02 mg/kg haloperidol doses caused significant decreases in percent hit. The 0.04 mg/kg haloperidol dose impaired performance of the task to the point that reliable choice accuracy measurements could not be made. Chronic nicotine infusion significantly diminished the impairing effects of haloperidol on performance during weeks 1–2. In summary, both typical and atypical antipsychotic drugs significantly impaired sustained attention in rats. Haloperidol was more detrimental than clozapine and risperidone. Chronic nicotine diminished the adverse effects of haloperidol on performance. This study establishes a paradigm to reliably determine the attentional impairment caused by antipsychotic drugs.

Multigenerational Exposure to Dietary Nonylphenol has No Severe Effects on Spatial Learning in Female Rats

Nonylphenol is a common intermediate in the production of many consumer compounds and reportedly acts as an estrogen mimic. Because estrogen affects the spatial learning and memory in rats, the effects of nonylphenol exposure on the performance of female rats in the Morris water maze were investigated. Here, Sprague–Dawley rats (F 0) consumed soy-free diets containing 0, 25, 200 or 750 ppm nonylphenol (≈0, 2, 16 or 60 mg/kg per day) beginning on postnatal day (PND) 42 and continuing for two generations (F 1 and F 2) with breeding occurring within treatments. Females to be behaviorally tested ( n=7–8 per treatment per generation) were ovariectomized at adulthood and assessed for spatial learning and memory between PND 125–150 (young adult age). Each rat was tested for four consecutive days (three trials per day) in the Morris water maze with the platform in a fixed location. One week later, each subject was primed with estrogen and progesterone and assessed on a single day (three trials). The F 1 rats continued on the same diets until PND 380–395 (middle aged) when they were re-tested as above (four consecutive days followed 1 week later with hormonal priming and a single test day). Latency to find the platform, path length and swim speed were averaged over the three trials per day and analyzed using repeated measures analyses of variance. There were no consistent effects of dietary nonylphenol exposure and no interactions of nonylphenol exposure on any measure of performance in either generation at the young age nor at the middle age in the F 1 generation. When tested at the young adult age, however, hormone priming resulted in latencies and path lengths that were significantly shorter than in those exhibited during the unprimed test days, and there was no such effect when tested at middle age. Middle aged rats exhibited better performance than the same animals tested at a young age, likely as a result of familiarity and practice with the test paradigm. These data suggest that multigenerational dietary nonylphenol exposure does not cause gross alterations in Morris water maze performance in young adult or middle aged ovariectomized female rats.

Chronic restraint stress enhances radial arm maze performance in female rats

Effects of chronic restraint stress (21 and 28 days) on physiological and behavioral parameters in female rats were examined. Total (bound and free) and free corticosterone (CORT) levels were measured at different time points during the stress period. Higher total CORT levels were observed in stressed rats during the stress period but returned to baseline at 15 days post-stress. Additionally, free CORT levels decreased across the stress period. Estrous cyclicity was monitored daily in all animals. Stress had no apparent effects on estrous cyclicity, in rats with either normal length or elongated estrous cycles, but stressed females gained less weight than controls. Following the stress period, subjects were tested for open field activity and radial arm maze (RAM) performance. Females stressed for 21 days showed enhanced spatial memory performance on the RAM. A longer period of restraint, 28 days, also led to less weight gain by stressed subjects and unaltered estrous cycle lengths, but was not associated with enhanced RAM performance. Further analysis indicated that RAM performance was influenced by specific estrous cycle day, particularly during proestrus. Following 21 days of restraint stress all animals in proestrus, regardless of treatment, showed impaired acquisition. After 28 days, stressed females in proestrus performed better than proestrus controls. These results are discussed in relation to previously reported effects of stress in male rats.

Prenatal morphine exposure differentially alters learning and memory in male and female rats

The present study tested the hypothesis that exposure to morphine on prenatal days 11–18 impairs performance on tasks requiring learning and memory in adult male and female rats. In Experiment 1, a symmetrical maze was used to measure learning. In Experiment 2, an eight-arm radial maze was used to assess working spatial memory. The results of Experiment 1 demonstrated that prenatal morphine exposure reduces the time needed to complete the trials, but does not affect the accuracy of performance in male rats. In contrast, prenatal drug treatment had no effects on either the time or the accuracy of performance in female rats. In Experiment 2, both male and female morphine-exposed rats needed more time to complete regular trials (no delay) than controls; however, morphine exposure in male rats did not affect performance on tasks requiring memory, measured with delay trials, but hindered it in ovariohysterectomized (OVX) female rats. In OVX females, replacement injections of both estrogen and progesterone restored the impairment of performance on delay trials produced by prenatal morphine exposure. Thus, the present study demonstrates that prenatal morphine exposure differentially alters performance of adult male and female rats on tasks requiring learning and spatial memory.

The partner preference paradigm: a method to study sexual motivation and performance of female rats

Sexual behavior of the female rat consists of initiative, as well as receptive components. Previous studies on female sexual behavior have focused on the reflexive response to a male's mount, i.e., the lordosis reflex, whereas the initiative and soliciting gestures that are exhibited by the female during copulation were ignored by most researchers. This bias led to a misconception of the female's role in the sexual act, according to which the female is passive and submissive, whereas the male rat is sexually dominant or even aggressive. In this paper, we describe a procedure, the partner preference paradigm, designed to investigate and quantify sexual motivation, initiation and solicitation in female rats. In this paradigm, the female can control the sexual act because the mobility of her sexual partner is limited. This setting enables to measure a variety of soliciting behaviors that reflect the active seeking of sexual contact by an estrous female. In addition, this paradigm enables the evaluation of the females' motivation to engage in a sexual act, by measuring the preference for a sexually appropriate over an indifferent partner. Moreover, the partner preference paradigm may be easily adopted for studies in male subjects, allowing the comparison of males' and females' responses to various experimental conditions. Themes: Neural basis of behavior Topics: Motivation and emotion; Hormonal control of reproductive behavior

Aflatoxin B 1 and Reproduction: I. Reproductive Performance in Female Rats

An experimental group of female rats was exposed to aflatoxin B1 at a dose of 7.5 mg/kg body weight daily for 14 days through oral intubation. A deleterious effect on the gonads and embryotoxicity in the experimental animals were observed. There were reductions in ovarian and uterine sizes, increases in fetal resorption, implantation loss, and intra-uterine death. The data showed significant disturbances in oestrus cycle, inhibition of lordosis, and reductions in the conception rates and litter sizes, suggesting severe impairment of fertility in the aflatoxin exposed rats. An aflatoxin blood level of 86.2 +/- 1.3 ppb was recovered in the experimental animals.

Ketanserin Effects on Rat Behavioral Responses: Modifications by the Estrous Cycle, Ovariectomy and Estradiol Replacement

DÍAZ-VÉLIZ, G., DUSSAUBAT, N. AND MORA, S. Ketanserin effects on rat behavioral responses: modifications by the estrous cycle, ovariectomy and estradiol replacement. PHARMACOL BIOCHEM BEHAV 57 [4]687–692, 1997.—The present investigation was designed to explore the influence of estrous cycle phase, ovariectomy, and estradiol replacement on the behavioral effects of the 5-HT 2 receptor antagonist, ketanserin.The parameters under investigation were ketanserin-influenced acquisition of conditioning avoidance responses (CARs), and the performance of some spontaneous motor behaviors. Ketanserin (KET 3 mg/kg) injected subcutaneously 30 min before testing improved active conditioned avoidance in intact female rats at estrus, and in ovariectomized (OVX) rats with estradiol replacement. Furthermore, KET impaired performance in female rats at diestrus and after ovariectomy. In male rats, which were included in this study in order to compare their behavioral responses with those exhibited by female rats, KET administration enhanced acquisition of CARs. These results provide behavioral evidence for the hypothesis that central serotonergic activity is a function of the hormonal status of the animal. An additional segment of the present study focussed on motoric behaviors. Spontaneous motor activity, number of rears, and time spent in grooming behavior were significantly increased by KET in all groups studied. In contrast, blockade of 5-HT 2 receptors failed to induce significant changes in the number of head shakes. Relationships between ovarian hormones and the central serotonergic system are discussed.

Effect of testosterone enanthate on follicular growth in rats

The effects of exogenous testosterone enanthate, a long-acting testosterone ester, on estrous activity and reproductive performance in female rats were studied. An injection of 2.5–20.0 mg of testosterone enanthate delayed until 26.9–60.1 days the cycling of the estrous cycle in a dose-dependent way; the treated rats began regular 4-day estrous cycles 41.9–80.7 days after the injection. Subsequent reproductive performance was not different in the treated and control animals (P > .05). Ovarian weight during estrous inhibition decreased steadily after treatment, but the uterine weight increased for a time. The ovaries contained follicles and interstitial cell islands, but no new ovulatory corpora lutea. The injection decreased the number of small follicles (250–549 μm), but increased the number of mature large follicles (≥550 μm; P < .05). The mean testosterone concentration in the peripheral plasma during estrous inhibition was higher than that before the treatment (P < .05). Testosterone concentrations increased for a time after treatment (P < .05), but decreased steadily thereafter. These results suggest that testosterone enanthate might be used for long-term contraception; the effects seem to depend on testosterone. Continuous stimulation by the long-term activity of testosterone inhibited the growth of small follicles but stimulated the growth of large follicles. © 1996 Wiley-Liss, Inc.

Effect of oxotremorine on the acquisition of a conditioned avoidance response is modified by the estrous cycle, ovariectomy, and estradiol replacement in rats

This study was designed to evaluate the influence of the hormonal status of the rat on the effects of a potent reversible muscarinic agonist, oxotremorine, on the acquisition of conditioning avoidance responses (CARs) and the performance of some spontaneous motor behaviors. Oxotremorine (OXO 50 and 100 μg/kg, intraperitoneally) given 5 min before testing improved active conditioned avoidance in intact female rats at estrus and in ovariectomized rats after estradiol replacement, and impaired performance in female rats at diestrus and after ovariectomy without estradiol replacement. No significant differences due to hormonal status of the rat in some spontaneous motor behaviors were observed. In fact, OXO in this dose range failed to induce significant changes in spontaneous motor activity, the number of rears diminished, and the time spent in grooming behavior increased in all groups studied. These results provided behavioral evidence for the hypothesis that central cholinergic activity is function of the hormonal status of the animal. Relationships between ovarian hormones and cholinergic system are discussed.

Influence of low birth weight on subsequent reproductive performance of female rats

Female rats which were born underweight had lower absolute body mass throughout the whole experimental period than female litter mates with normal birth weight (controls). Their reproductive performance observed during three consecutive pregnancies was not different from that of controls except for lower litter size in the 1st pregnancy. Thus at least for rats, low spontaneous birth weight of females does not indicate subsequent poor pregnancy outcome.

The effect of feeding endophyte infected tall fescue seed on reproductive performance in female rats

1. Female Sprague-Dawley rats ( Rattus norvegicus) were randomly assigned to diets containing mixtures of rat chow and tall fescue ( Festuca arundinacea) seed with 0, 5, 10, 20 and 40% infection levels of Acremonium coenophialum to assess the effect of the diets on the reproductive potential of rats. 2. Rats fed 40% infected seed had decreased body weight, decreased mean percent body weight of uteri, failed to maintain normal estrous cycles and were unable to become pregnant. 3. Animals fed a diet of 20% infected fescue seed had extended estrous cycles. 4. There were no significant differences among the 0, 5 and 10% dietary treatments.

Uterine position and conditioned taste aversion.

Three experiments were designed to determine the influence of uterine position on the performance of female rats in a conditioned taste aversion paradigm. The first and second experiments confirmed a differential behavioral response by males and females during acquisition and extinction of the conditioned taste aversion. However, no differences were found between females that had caudal male littermates in utero (MF) and females that had no caudal male littermates (FF). In the third experiment, in which testosterone was administered to females throughout testing, MF females showed an increased sensitivity to testosterone and a more prolonged rate of extinction than FF females. Exposure to testosterone during prenatal development heightened postnatal responsiveness to testosterone in female rats. The results are discussed in terms of the organizational and activational effects of testosterone on behavior in a conditioned taste aversion situation.

Gender differences in visual discrimination by rats in response to malnutrition of varying durations

Visual discrimination of hooded rats was tested at 3 months of age by a Lashley procedure. Three groups of rats were used: those with histories of protein deprivation for up to 20 generations, those with protein deprivation for a single generation, and well-nourished controls. Growth retardation was present to a similar degree in both genders of the 2 malnourished groups. Deficits in visual discrimination were observed in female animals with intergenerational malnutrition, but not in females with single-generation malnutrition. Males with intergenerational and single-generation malnutrition showed equal deficits in visual discrimination. These findings demonstrate that the performance of female rats is impaired only after prolonged exposure to malnutrition, whereas males are vulnerable after shorter periods.

RESPONSE OF MALE AND FEMALE WEANLING RATS TO DIETS OF DIFFERENT DIGESTIBLE ENERGY CONCENTRATIONS AND TO SUPPLEMENTATION WITH VITAMIN E, USING BARLEY OR WHEAT AS CEREAL SOURCES

Sixty-four weanling rats were used in an experiment lasting 6 weeks to test the response of male and female rats to diets having 2.8, 3.0, 3.2, and 3.4 Mcal digestible energy (DE) per kg, where barley and wheat were used as the cereal sources and diets were supplemented with 22 IU vitamin E/kg or unsupplemented. The use of wheat or barley did not influence the performance of female rats but males utilized barley-based diets better than wheat diets and gained more in some weeks, though not overall. Male rats did not respond to vitamin E supplementation but females consumed more of the vitamin E-supplemented diets and grew 6% faster (P &lt; 0.10). Except in the 1st week, females ate more of the lower energy than of the higher energy diets and so DE concentration did not influence rate of gain. Males were not able to adjust food intakes to compensate for dietary energy levels and needed a DE concentration of 3.2 Mcal/kg diet for maximum growth. The data indicate that there is a sex difference in growing rats insofar as DE concentration of the diet required for maximum gain is concerned.

Effect of iodine deficiency on the reproductive performance of female rats and the viability and growth rate of their progeny

The experimental period was apparently too short and the number of rats too small to demonstrate a significant effect of iodine deficiency on some indices of reproduction of the females and the growth rate of their progeny. It was found, however, that iodine deficiency: a) delayed significantly the conception of the second generation females (C2) (Table 3) but was quite ineffective in the first generation females (B1, C1) (Tables 2 &amp; 4), b) did not significantly affect the number of pups dropped or their birth weight, c) increased pup mortality during suckling period, d) tended to decrease the weight of the female sex organs of adult rats (Table 5), e) increased the absolute thyroid weight more rapidly in young growing rats than in old fullgrown rats (Tables 3, 4 &amp; 5), and more rapidly in growing males than females, f) decreased significantly and progressively the PBI level in the serum of adult females which had pregnancies and lactations, g) obviously adversely affected the milk secretion of C1 rats during their second lactation on iodine deficient diet (Experiment II) as judged from the growth rate of their pups during 0—15 days after birth, h) did not adversely affect the growth rate of the suckling offspring of the dams during their first lactation on iodine deficient diet (Tables 3 &amp; 4), i) did not significantly affect the rate of gain of the young rats from weaning up to 60-days of age. The rats transferred from iodine deficient to commercial diet at weaning had larger body weights and smaller thyroids at the age of 60 days than their litter mates remaining on an iodine deficient diet (Table 4). There is of course a possibility that the commercial diet was more palatable than the semisynthetic diet. It is also possible that the iodine deficiency activated the thyroid during the preweaning period and that after the transfer to iodine containing commercial diet at weaning, more thyroxine was secreted from preactivated glands compared to thyroids of the controls or thyroids of the rats kept on an iodine deficident diet throughout the growth period. Thyroid hormones are required for normal growth. A hypothyroid condition favours the accumulation of water and fat into the body tissues and may by this way result in an increase of the body weight. ln this study, however, no attempt was made to estimate the fat content of the body of the experimental rats.

Estrous Cycle in the Rat: Effects on Self-Stimulation Behavior

The performance of female rats, in pressing a bar for electrical stimulation of the hypothalamus, changes during the estrous cycle. Highest barpressing rates accompany the appearance of vaginal cornification. This increase is not an artifact of increased spontaneous activity at estrus, although the factors underlying these changes in activity may also mediate the changes in self-stimulation behavior.