Cage Control Group Research Articles

Exercise suppresses macrophage antigen presentation.

This study determined the effects of exercise on the ability of macrophages (Mphi) to present antigen to T cells. Pathogen-free male Balb/c mice (8 +/- 2 wk of age) were randomly assigned to either home cage control, moderate exercise (Mod; 18 m/min, 5% grade, 0.5 h/day), exhaustive exercise (Exh, 18-30 m/min, 3 h/day), or treadmill control groups. The mice underwent treatments for 4 days during peritoneal thioglycolate inflammation. Peritoneal Mphi were harvested, purified, and incubated with chicken ovalbumin (C-OVA; 0-10 mg/ml) for 18 h. Mphi were then cocultured with C-OVA-specific T cells for 48 h, and the supernatants were analyzed via ELISA for interleukin-2 as an indication of Mphi antigen presentation (AP). Exh exhibited suppressed ( approximately 25-34%) Mphi AP across a wide range of C-OVA doses when measured immediately, 3, and 24 h postexercise. In contrast, Mod had reduced Mphi AP only at 3 h postexercise. Mphi AP was also lower in the treadmill control (4-27%) compared with the home cage control group, but was significantly higher than Exh. The reduction in Mphi AP was not due to exercise-induced differences in Mphi number, percentage, or expression of intercellular adhesion molecule-1, B7-2, or major histocompatability complex II, molecules important in AP. In conclusion, our data lend evidence that may help explain the increased incidence of infection observed after prolonged exhaustive exercise or overtraining.

EXHAUSTIVE EXERCISE DECREASES MACROPHAGE ANTIGENIC PEPTIDE GENERATION

1146 The ability of macrophages to generate antigenic peptides is central to antigen presentation and the development of specific T cell mediated immunity. We and others have documented that exhaustive exercise may decrease several functions of macrophages such as antigen presentation and MHC II expression, while other functions are increased such as phagocytosis and oxidative burst activity. However, the impact of exhaustive exercise on macrophage antigenic peptide generation has never been examined. Therefore, this study determined the effects of exhaustive exercise on the ability of macrophages to generate antigenic peptides. In two experiments pathogen-free young male Balb/c mice (n=16, 8 wk) were randomly assigned to either exhaustive exercise (EXH, n=8) or home cage control (HCC, n=8) groups. The mice were exercised on a treadmill exhaustively (15-40 m/min, 5 percent grade, 2.5-3 hr/d) for a period of 4 days during a peritoneal thioglycolate inflammation. Animals were sacrificed immediately post-exercise on day 4 and the macrophages were aseptically harvested by peritoneal lavage. The macrophages were washed, adjusted to appropriate concentrations, plated and allowed to adhere to the plates for 18 hr. After removal of all non-adherent cells, the macrophages were cultured with 10 mg/mL of FITC-labeled ovalbumin for 2-4 hr. During the 2-4 hr incubation the macrophages phagocytose and cleave the ovalbumin generating fluorescent antigenic peptides. The cells were removed by teflon cell scrapers and only live cells were analyzed by flow cytometry for determination of antigenic peptide generation. There was a significant [F(1,7)=26.84, P=0.0066] suppression in antigenic peptide generation due to exhaustive exercise. These results may explain why macrophage antigen presentation is suppressed following exhaustive exercise.

The restraint stress-induced reduction in lymphocyte cell number in lymphoid organs correlates with the suppression of in vivo antibody production

In this study, we examined the effects of restraint stress on some immune parameters such as the in vivo antibody levels, cytokine production, and lymphocyte cell number in the spleen or mesenteric lymph node (MLN). BALB/c mice were thus injected intraperitoneally 2-times with OVA absorbed into alum on days 0 and 21. Before the first injection, the animals were either restrained for 12 h (stress group) or returned to their home cage (control group). Exposure to stress resulted in a reduction in the serum levels of anti-OVA IgE, IgG1, and IgG2a. In addition, stress also caused a decrease in the IL-4 and IFN- γ levels in the spleen or mesenteric lymph node cell culture supernatants. Furthermore, exposure to stress resulted in a decrease in the splenic and mesenteric lymphocyte cell number when examined immediately after the cessation of stress. This decrease persisted for at least 12 h after the termination of stress and thereafter disappeared 24 h after stress. The stress-induced reductions in antibody and cytokine production occurred only when antigen was given either immediately or 6 h after stress, but not when antigen was given 24 h post stress. These results thus suggest that the restraint stress-induced change in lymphocyte cell number in the spleen or MLN closely correlates with the altered antibody and cytokine levels.

The Effects of Voluntary Exercise and Immobilization on Humoral Immunity and Endocrine Responses in Rats

Baldwin, D. R., Z. C. Wilcox and G. Zheng. The effects of voluntary exercise and immobilization on humoral immunity and endocrine responses in rats. Physiol Behav 61(3) 447–453, 1997.—This research examined the effect of type of stressor (physical vs. psychological) on humoral immunity and neuroendocrine responses in male and female rats. Eighty adult Sprague–Dawley rats were assigned to one of the four stress conditions ( n = 20 animals/group): 1. Voluntary running (high physical/low psychological stress); 2. immobilization (low physical/high psychological stress); 3. mixed stress (running and immobilization); and 4. cage control group. The experimental manipulations were conducted over a 6-week period for 4 h/day. Five weeks after the start of the study, all animals were immunized with 1 ml of a 10% suspension of sheep red blood cells (SRBC) in saline and sacrificed 1 week later. Data analyses revealed no main effect of stress on any of the immune or endocrine parameters. However, strong gender differences emerged within the stress conditions on these physiological parameters. The stressed female rats displayed an enhanced antibody response to SRBC and a higher percentage of peripheral blood lymphocytes than their male counterparts. However, there were no significant differences between the male and female control animals with respect to these variables. Female rats consistently displayed elevated levels of plasma corticosterone and adrenal norepinephrine across all conditions. In addition, female rats displayed heavier relative organ weights (adrenal and spleen). Taken together, the notion of differential immunity with respect to physical or psychological stress is not supported by the present study.

Androgen inhibits neurotransmitter turnover in the medial prefrontal cortex of the rat following exposure to a novel environment

Previous studies have demonstrated that gonadal steroid hormones affect the neuroendocrine response to a novel environment and other stressors. Introduction to a novel environment also increases neurotransmitter turnover in the medial prefrontal cortex (MPFC). In this study, we examined the possibility that gonadal steroid hormones could similarly modulate the neurotransmitter response to a novel environment in the MPFC of the male rat. Male Fischer 344 rats at 3 months of age were gonadectomized (GDX'd) and implanted with Silastic capsules containing dihydrotestosterone propionate (DHTP, a non-aromatizable form of androgen), 17 β-estradiol (E), or placebo. Control animals were left intact. Each of these groups was further divided into a group introduced to a novel environment or a home cage control group. Animals exposed to a novel environment were killed after spending 20 min in a novel open field, whereas control animals were killed immediately upon removal from their home cage. Using high performance liquid chromatography, the MPFC was assayed for tissue levels of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylalanine (DOPAC) and homovanillic acid (HVA); norepinephrine (NE) and its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG); or serotonin (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA). The introduction to a novel environment caused significant increases in turnover of all three neurochemicals examined as estimated by metabolite/precursor ratios. These increases were characterized by increases in DOPAC, HVA, MHPG and 5-HIAA coupled with decreases in DA, NE and 5-HT. There was no effect of GDX on neurotransmitter turnover, however, treatment of GDX animals with DHTP prevented the open field induced increase in DOPAC/DA, MHPG/NE, and 5-HIAA/5-HT ratio. Treatment of GDX animals with estrogen had the opposite effect of DHTP, DOPAC/DA and MHPG/NE ratios increased to a greater level following the introduction to a novel environment than in GDX or intact animals. Examination of behavior in the open field showed significant decreases in activity in the DHTP-treated group but not in any other behavioral parameter (rears, nose pokes). Since the non-aromatizable androgen, DHTP, is presumably acting via androgen receptors, and E is presumably acting via estrogen receptors, these data suggest that, in the MPFC of male rats, androgen and estrogen receptors act in an opposing fashion to modify neurotransmitter turnover. This suggests that local changes in the relative levels of androgen and estrogen can have profound effects on the neurobiological response of the medial prefrontal cortex to stimuli.© 1997 Elsevier Science B.V. All rights reserved.

Changes in monoamines and their metabolite concentrations in REM sleep-deprived rat forebrain nuclei

Rapid eye movement sleep deprivation (REMSD) is a potent Stressor in rats. Behavioral abnormalities such. as passive and active avoidance, locomotor activity, problem solving, sensory information processing, and the development of adaptive copping strategy in response to repeated stress are among the earliest obvious symptoms of REMSD, the mechanism for which remain largely unknown. The aim of this study was to determine whether 96 h of REMSD causes changes in monoamine neurotransmitters concentrations in rat forebrain regions (frontal cortex, FC; parietal cortex, PC, and striatum) that are involved in mediating higher brain functions such as attentional mechanisms, sensory information processing, and locomotor activity, which are severely affected in REMSD conditions. Rats were subjected to 96 h of REMSD using inverted flower pot water tank technique. To account for the stress associated with water tanks, a tank control group (TC) was included where the animals could reside comfortably on a large pedestal in the water tank. Regional brain concentrations of norepinephrine (NE), dopamine (DA), dihydroxyphenyacetic acid (DOPAC), l-3,4-dihydroxyphenylalanine ( l-DOPA), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (HIAA) were determined by electrochemical detection using high-performance liquid chromatography. The concentrations of serotonin and its metabolite, HIAA, was reduced in the frontal and parietal cortexes of REMSD rats compared with TC or cage control (CC) group. NE, DA, DOPAC, and HVA concentrations in FC and PC of REMSD animals were remained unchanged compared with TC or CC rats. A significant increase in the concentrations of DA metabolites was observed in the striatum of REMSD rats when compared with CC and TC rats. There was a 29 and 31% increase in the concentration of striatal DA in REMSD group compared to the TC and CC groups, respectively; however, these percentages were not statistically different. Striatal NE, 5-HT, and HIAA concentrations were not significantly different among the three groups. These results suggest that 96 h of REMSD alters dopaminergic and serotonergic systems in different locations in rat brain. The effect of REMSD on the serotonergic systems are localized in the cerebral cortex, whereas dopaminergic metabolism is increased in the striatum.

EFFECTS OF EXERCISE COUNTERMEASURES ON HINDLIMB PASSIVE TENSION IN 7 DAY SUSPENDED RATS 990

Previously we have shown that hindlimb passive tension significantly increases during 7 days of suspension unloading. The purpose of this study was to determine the effectiveness of 3 exercise protocols in attenuating this increased tension and examine possible mechanisms. Male rats were assigned to a cage control (C) group or a suspended (S) group with or without exercise. Hindlimb passive tension was measured noninvasively with the ankle dorsiflexed on days 0 and 7 by a passive tension apparatus. On days 2, 4, and 6, all animals were removed from their cages or suspension, weighed, anesthetized and exercised or sham-treated, then returned to their cages or suspension apparatus. The 3 exercise protocols employed were: 1) passive static stretching, 2) treadmill walking, and 3) electrically-induced resistive weight training. Hindlimb passive tension significantly increased in all S groups following suspension. All 3 exercise countermeasures significantly attenuated(weight training 70%, walking 50%, and stretching 35%) the increased passive tension that occurred during suspension unloading. Soleus and gastrocnemius muscle hydroxyproline indicated no changes in collagen content of either muscle and muscle lengths were not different between C and S animals after 7 days of suspension. Suspension-induced increased passive tension was not due to absolute muscle shortening or collagen content. Possible mechanisms of altered tension may include changes in extracellular matrix, muscle cytoskeleton, or fiber arrangement. It is concluded that for optimum attenuation of passive tension increases brought about by nonweight bearing disuse conditions, forceful repeated contractions through a full range of motion are required.

REM sleep deprivation alters dopamine D 2 receptor binding in the rat frontal cortex

REM sleep deprivation (RSD) of rats results in facilitation of dopaminergic behavior and an increase in striatal D 2 receptor density. To determine whether RSD results in changes in D 2 receptor in other brain regions, receptor affinity ( K d) and density ( B max) were measured in the anteromediofrontal (AM), cingulate (CN), and sulcal cortex (SL) in four groups of rats: 1), RSD96 group (RSD for 96 h; small pedestal/water tank method), 2) RSD24 group (large pedestals for 72 h then small pedestals for 24 h), 3) tank control group (TC; large pedestals for 96 h), and 4) cage control group. In separate groups, ambulation was recorded for 30 min following treatments. Group RSD96 showed an increase in activity compared to TC, and TC was increased compared to CC ( p < 0.05 for all). In group RSD24, the AM showed an increase in B max and K d ( p < 0.05), but there were no effects by RSD96. In the CN, B max and K d were decreased by RSD96 ( p < 0.05) but not RSD24. In the SL, B max was increased by RSD96, but not RSD24, whereas K d was increased in both RSD groups ( p < 0.05).

Pituitary and peripheral thyroid hormone responses to thyrotropin-releasing hormone during sustained sleep deprivation in freely moving rats.

Sleep deprivation is associated with poor cognitive ability and impaired physical health, but the ways in which the brain and body become compromised are not understood. In sleep-deprived rats, plasma total T4 and T3 concentrations decline progressively to 78% and 47% below baseline values, respectively, brown adipose tissue 5'-deiodinase type II activity increases 100-fold, and serum TSH values are unknown. The progressive decline in plasma thyroid hormones is associated with a deep negative energy balance despite normal or increased food intake and malnutrition-like symptoms that eventuate in hypothermia and lethal systemic infections. The purpose of the present experiment was to evaluate the probable causes of the low plasma total T4 during sleep deprivation by measuring the free hormone concentration to minimize binding irregularities and by challenging the pituitary-thyroid axis with iv TRH to determine both 1) the pituitary release of TSH and 2) the thyroidal response of free T4 (FT4) and free T3 (FT3) release to the TSH increment. Sleep-deprived rats were awake 91% of the total time compared with 63% of the total time in yoked control rats and 50% of the total time during the baseline period. Cage control comparison rats were permitted to sleep normally. Sustained sleep deprivation resulted in a decline from baseline in plasma FT4 of 73 +/- 6% and FT3 of 45 +/- 12%, which were similar to the declines in total hormone concentrations observed previously; nonstimulated TSH was unchanged. In the yoked and cage control groups, FT4 also declined, but much less than that of the sleep-deprived group. The relative changes in free compared with total hormone concentrations over the study were also less parallel than those in the sleep-deprived group. The plasma TSH response to TRH was similar in all groups across experimental days. The plasma FT4 and FT3 concentrations in sleep-deprived rats increased after TRH-stimulated TSH release to an extent comparable to control values. Taken together, low basal FT4 and FT3 hormone concentrations and unchanged TSH and thyroidal responses to TRH suggest a pituitary or hypothalamic contribution to the hypothyroxinemia during sleep deprivation.

The effect of ultrasound exposure in utero on the development of the fetal mouse testis: Adult consequences

The effects of exposure in utero to 1 MHz, continuous-wave ultrasound on adult growth and testicular development in the mouse was investigated. The spatial peak temporal average intensity ( I spta ) employed ranged from 1 to 10 W/cm 2, with exposure durations ( t) of 200 s to 20 s. Exposures were made on days 9, 12 or 15 of gestation. Results showed an increase in postpartum deaths, an increase in the number of stillbirths, and a decrease in litter size when I 2 t ≥ 1125 W 2 s/cm 4, such that there was significant loss of pups. Birthweights of pups from nearly all dosage groups was significantly lower than that of the sham or cage control groups. Results also showed that males exposed to ultrasound in utero had decreased testis size and decreased daily sperm production ranging from 9% to 30%. This study showed that ultrasound exposure in utero is capable of disrupting fetal development and having potential subsequent effects on fertility in the adult male.

Circularly polarized 50-Hz magnetic field exposure reduces pineal gland and blood melatonin concentrations of Long-Evans rats

In order to determine if pigmented rats also exhibit melatonin suppression like that described for albino rats exposed to circularly polarized, 50-Hz, 1-μT magnetic fields for 6 weeks, two experiments were conducted with male Long-Evans rats. The field-exposed experimental group received circularly polarized, 50-Hz, 1-μT magnetic fields for 6 weeks, the concurrent sham-exposed control group was exposed to the stray field of 0.02 μT. In addition, prior to the exposure experiment, two cage-control groups were placed in the facility for 6 weeks without activation of the 50-Hz magnetic field generation apparatus. Rats were sacrificed at 12.00 and at 24.00 h for collection of plasma and pineal gland: melatonin was determined by radioimmunoassay. Significant reductions of plasma and pineal gland melatonin contents were observed at 0.02 μT as compared to the control values, and a further reduction was observed at 1 μT. As do albino rats, pigmented rats also exhibit melatonin suppression when exposed to time-varying magnetic fields.

Raised corticosterone in the rat after exposure to the elevated plus-maze

Rats given one or two 5-min trials in the elevated plus-maze had plasma corticosterone concentrations significantly higher than the home cage control group and there was no sign of habituation in the group given two trials. In rats given two plus-maze trials the corticosterone responses were significantly higher in the group given 10-min rather than 5-min trials. A previous experience of cat odour (1 week earlier) has no effect on the plasma corticosterone response, but did have an anxiogenic effect that could be detected by a decrease in the percentage of time spent on the open arms of the plus-maze. The results are discussed with reference to the nature of anxiety generated by trials 1 and 2 and by the trial duration in the plus-maze, and with respect to dissociation between behavioural and endocrinological measures.

Microinjections of flupenthixol into the caudate putamen of rats produce intrasession declines in food-rewarded operant responding

Results of recent studies suggest that dopamine (DA) transmission in the caudate putamen may be involved in food reward-related learning. The purpose of the present study was to evaluate the contribution of DA terminals in the dorsal caudate putamen to food-rewarded operant responding. Experiment 1, a study measuring circling behavior in 18 rats receiving systemic amphetamine (1.5 mg/kg) and unilateral intracaudate putamen injections of cis-flupenthixol (0.0, 1.0, 10.0, and 25.0 μg in 0.5 μl), a DA receptor antagonist, or its pharmacologically inactive isomer trans-flupenthixol (25.0 μg in 0.5 μl), determined a behaviourally effective dose of cis-flupenthixol. Results showed that cis-flupenthixol dose dependently increased ipsiversive turning and trans-flupenthixol did not. In Experiment 2, an operant study, 36 rats were trained to press a lever for food on a variable interval 30-s schedule. Rats were then randomly assigned to four groups, three of which received one of the following bilateral intracaudate injections prior to three subsequent test sessions: saline ( n = 6; 0.5 μl), cis-fluoenthixol ( n = 10; 25.0 μg/0.5 μl), and trans-fluoenthixol ( n = 10; 25.0 μg/0.5 μl). Rats in the home cage control group ( n = 10) received two bilateral intracaudate putamen injections of cis-flupenthixol (25.0 μg/0.5 μl) in their home cages and a final injection of cis-flupenthixol prior to a test session. The results showed that cis-flupenthixol, but not trans-flupenthixol or saline, produced a time-dependent intrasession decline in operant responding. This pattern resembled that seen in extinction. The intrasession pattern of responding in the home cage control did not differ significantly from that of the first test day but did differ significantly from that of the third test day of the cis-flupenthixol group, suggesting that the extinction-like pattern of responding in the cis-flupenthixol group was not a result of repeated central injections per se. These results provide support for the hypothesis that DA transmission may be involved in incentive learning and, further, that dopaminergic projections to the dorsal caudate putamen may play a role in food reward-related incentive learning.

The effect of cigarette smoking on rabbit aortic elastase activity

Twenty rabbits were divided into three groups: (1) cage controls, (2) machine controls, and (3) cigarette exposed. The cigarette-exposed group was exposed to two 2-R1 reference cigarettes a day for 6 weeks on a Walton-II (Process and Instruments Corp., Brooklyn, N.Y.) smoking machine. Rabbits in the machine control group were placed in the smoking machine for the same period of time without cigarettes. Cage control animals were not placed in the smoking machine. Aortic elastase was significantly higher in the cigarette-exposed group (21.11 ± 6.15) compared to both the cage control group (3.11 ± 1.11) and machine control group (14.66 ± 4.69). Aortic elastase in the machine control group was significantly higher in smoke-exposed rabbits than in both cage contol and machine control rabbits. These data indicate that cigrette smoking increases aortic elastase activity in rabbits. If these data were to be extrapolated to humans, then patients with abdominal aortic aneurysms who smoke may have an accelerated rate of aneurysm growth or earlier rupture or both.

The role of nicotine in the pathogenesis of pulmonary emphysema.

An investigation was undertaken to evaluate the potential role of nicotine in the pathogenesis of pulmonary emphysema. The acute lethality and the pulmonary toxicity of a single endotracheally administered dose of nicotine were studied in Long-Evans rats. The 24-h LD50 of nicotine was established at 19.3 +/- SD 5.4 mg/kg. Subsequently, rats were treated with either nicotine alone (3 or 7.5 mg/kg), porcine pancreatic elastase (PPE) alone (200 IU/kg) or PPE (200 IU/kg) followed 5 days later by nicotine (3 mg/kg). The selected dose of PPE was below the threshold dose for induction of emphysematous lesions. Cage and sham-treated control groups also were included in the investigation. Four weeks after treatment, extensive physiologic tests were conducted to evaluate the ventilatory, mechanical, and gas exchange functions of the lungs. Lung tissue specimens also were taken for estimation of tissue volume density. Although a few isolated incidents of significant intergroup differences were observed, no distinctive pattern of functional or structural change reminiscent of emphysema was noted in any of the experimental groups. It is concluded that endotracheal instillation of a single, relatively high, dose of nicotine neither induces nor augments the development of pulmonary emphysema in the rat.

Serotonergic changes in specific areas of rat brain associated with activity--stress gastric lesions.

To study serotonergic involvement in the development of gastric lesions following activity wheel stress, three groups of rats (gastric lesions, no gastric lesions, and home--cage controls) were killed following exposure to the experimental procedures. The brains were dissected into eight specific areas and subjected to analyses for serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) using high performance liquid chromatography with EC detection. Lower levels of 5-HT were found in the midbrain, cortex, and hippocampus of rats with gastric lesions compared to either the no lesion group, subjected to shorter periods of activity--stress, or the home--cage control group. Levels of 5-HT and 5-HIAA were elevated in the pons/medulla oblongata of both the lesion and the no lesion groups compared to the home--cage controls. Corticosterone levels in blood were also significantly elevated in the lesion group. These data on serotonin changes in the CNS suggest a possible role for this neurotransmitter in stress-induced gastric pathology.