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PubMed2001

Involvement of 5-HT(2C) receptors in the anti-immobility effects of antidepressants in the forced swimming test in mice.

Several recent studies have demonstrated that 5-HT(1A), 5-HT(1B) and 5-HT(3) receptors were implicated in the mechanism of action of antidepressants in the mouse forced swimming test. Despite extensive evidence for a role of 5-HT(2C) receptors in depression, the precise role of these receptors in the effects of clinically established antidepressants was not directly investigated in the mouse forced swimming test. This work was aimed at exploring interactions between several doses of Ro 60-0175, a recently available, full and selective 5-HT(2C) agonist, and antidepressant drugs in the mouse forced swimming test. Spontaneous locomotor activity was measured as an index of intact sensorimotor functions and the dose-effect of Ro 60-0175 alone, as well as interactions with several antidepressants, such as tricyclic antidepressants (imipramine, desipramine and maprotiline) and selective serotonin reuptake inhibitors (paroxetine, citalopram, fluoxetine, fluvoxamine and sertraline), were studied in the mouse forced swimming test. There was no intrinsic antidepressant-like effect of Ro 60-0175, but an impairment in locomotor function was detected when using doses higher than 4 mg/kg in the mouse. There was a synergistic effect of low doses of Ro 60-0175 with sub-active doses of imipramine, paroxetine, citalopram and fluvoxamine; an antagonism between the highest dose of Ro 60-0175 and the active doses of paroxetine and fluoxetine was also detected. There is evidence that 5-HT(2C) receptors may be involved in the action of antidepressants which are able to boost the concentration of serotonin in the synapse, i.e. SSRIs and imipramine

Animals↗
PubMed2002

In the rat forced swimming test, NA-system mediated interactions may prevent the 5-HT properties of some subacute antidepressant treatments being expressed.

In the rat forced swimming test (FST), reuptake inhibitors selective of either serotonin (5-HT) or noradrenaline (NA) decrease immobility duration, and increase, respectively, swimming and climbing behaviour. In this study, an almost total 6-OHDA-induced NA-depletion prevented the behavioural effects of desipramine, but not fluoxetine. Interestingly, the serotonin/noradrenaline-reuptake-inhibitor milnacipran, as well as a (desipramine+fluoxetine) combination, could produce both swimming and climbing behaviour in NA-lesioned rats, but not in non-lesioned. The new antidepressant mirtazapine, which enhances both 5-HT and NA transmissions, supposedly through the antagonizing of alpha(2)-adrenoreceptors, dose-dependently reduced immobility and increased climbing behaviour. Interestingly, a (mirtazapine+fluoxetine) combination treatment resulted in additive anti-immobility effects and in the summation of fluoxetine-induced swimming with mirtazapine-induced climbing. Taken together, these data suggest that the NA system mediates presynaptic inhibiting interactions on the 5-HT system, that may involve alpha(2)-receptors, and that may limit the efficacy of mixed serotonin/noradrenaline reuptake inhibition in subacute antidepressant treatments.

Adrenergic alpha-Antagonists↗
PubMed1999

An investigation of the antidepressant properties of lofepramine and its desmethylated metabolites in the forced swim and olfactory bulbectomized rat models of depression.

The purpose of this study was to examine the metabolites of lofepramine (LOF), namely desipramine (DMI), desmethyl desipramine (DDMI) and desmethyl lofepramine (DML) in the forced swim and olfactory bulbectomized (OB) rat models of depression. In the first study, subacute treatment with DMI (10 mg/kg) and DML (20 mg/kg), but not LOF, reduced the immobility time in the forced swim test. In the "open field", chronic (14 day) treatment with all drugs attenuated the hyperactivity associated with olfactory bulbectomy. In the second experiment, a lower dose of DML (10 mg/kg) demonstrated activity following subacute treatment in the forced swim and following chronic treatment in the OB model. In addition, DDMI (10 mg/kg) was active in both models. From these results, it can be concluded that, at the doses employed, LOF and it's desmethylated metabolites, DMI, DML and DDMI, exhibits activity in the OB model. In contrast, lofepramine but not it's desmethylated derivatives is inactive in the forced swim test, perhaps suggesting the requirement of metabolic conversion of LOF to reveal antidepressant activity in this model.

Animals↗
PubMed1994

Regional and fibre type glycogen utilization patterns in the hamster diaphragm following swimming.

The purpose of this study was to determine the regional and myofibrillar ATPase (M-ATPase) fibre type glycogen utilization patterns in response to increased ventilation induced by pre-exhaustive (Pre-Exh) and exhaustive (Exh) durations of swimming. Twenty-eight hamsters were studied: six controls (Con), 11 Pre-Exh (swam 82 min), 11 Exh (swam to exhaustion). We examined the optical density of PAS-stained fibres from the different regions of the diaphragm as a measure of glycogen remaining after the exercise or control period. The optical densities of PAS-stained fibres in most M-ATPase fibre types and diaphragmatic regions for the Pre-Exh and Exh groups was less than those in the Con hamsters except for the optical densities of all the M-ATPase fibre types in the sternal region. The optical densities of PAS-stained fibres in different regions and M-ATPase fibre types did not differ in the Exh and Pre-Exh groups. This data indicates that significant glycogen utilization occurred in all three M-ATPase fibre types in the costal, and both the thoracic and abdominal surface of the crural diaphragm in hamsters following pre-exhaustive and exhaustive durations of swimming. Glycogen utilization was greater in type 1 fibres of the thoracic surface of the crural region than in the type 1 fibres of the sternal region of the Pre-Exh group. Further, significant utilization of glycogen did not occur in any of the three M-ATPase fibre types of the sternal region of the diaphragm following prolonged durations of swimming. It would appear that glycogen is an important substrate in the hamster diaphragm during swimming.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed2001

Maximal lactate steady state in rats submitted to swimming exercise.

The higher concentration during exercise at which lactate entry in blood equals its removal is known as 'maximal lactate steady state' (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in rats during swimming exercise. Adult male Wistar rats, which were adapted to water for 3 weeks, were used. After this, the animals were separated at random into groups and submitted once a week to swimming sessions of 20 min, supporting loads of 5, 6, 7, 8, 9 or 10% of body wt. for 6 consecutive weeks. Blood lactate was determined every 5 min to find the MLSS. Sedentary animals presented MLSS with overloads of 5 and 6% at 5.5 mmol/l blood lactate. There was a significant (P<0.05) increase in blood lactate with the other loads. In another set of experiments, rats of the same strain, sex and age were submitted daily to 60 min of swimming with an 8% body wt. overload, 5 days/week, for 9 weeks. The rats were then submitted to a swimming session of 20 min with an 8% body wt. overload and blood lactate was determined before the beginning of the session and after 10 and 20 min of exercise. Sedentary rats submitted to the same acute exercise protocol were used as a control. Physical training did not alter the MLSS value (P<0.05) but shifted it to a higher exercise intensity (8% body wt. overload). Taken together these results indicate that MLSS measured in rats in the conditions of the present study was reproducible and seemed to be independent of the physical condition of the animals.

Anaerobic Threshold↗
PubMed2001

Critical swimming speed: its ecological relevance.

Critical swimming speed (U(crit)) is a standard measurement to assess swimming capabilities of fishes. To conduct this measurement a fish is introduced into a water tunnel in which the current velocity can be controlled by the investigator. At the beginning of the measurement water velocity is low, approximately 1 body length (BL) s(-1), and is then incrementally increased at prescribed intervals. Fishes tend to maintain their position in the water tunnel against the current until fatigue sets in. The time and velocity at which the fish fatigue are used to calculate the critical swimming speed. This procedure is widely used to assess the effects of environmental conditions and pollutants on fish performance. Since the procedure is conducted in conditions that are far from representing most natural environment experienced by fishes, doubts have been raised about its ecological and ecophysiological relevance. Few studies examined correlations between critical swimming speed and traits that seem to be more ecologically relevant. Positive correlations were found between U(crit) and routine activity, metabolic rates and body size of open water, planktivorous fishes, metabolic rates and body size. These data indirectly suggest ecological relevancy of U(crit), but direct measurements relating U(crit) to reproductive success or survival are required to assess such relevancy.

Animals↗
PubMed2002

Beyond U(crit): matching swimming performance tests to the physiological ecology of the animal, including a new fish 'drag strip'.

Locomotor performance of animals is of considerable interest from management, physiological, ecological and evolutionary perspectives. Yet, despite the extensive commercial exploitation of fishes and interest in the health of various fish stocks, the relationships between performance capacity, natural selection, ecology and physiology are poorly known for fishes. One reason may be the technical challenges faced when trying to measure various locomotor capacities in aquatic species, but we will argue that the slow pace of developing new species-appropriate swim tests is also hindering progress. A technique developed for anadromous salmonids (the U(crit) procedure) has dominated the fish exercise physiology field and, while accounting for major advances in the field, has often been used arbitrarily. Here we propose criteria swimming tests should adhere to and report on several attempts to match swimming tests to the physiological ecology of the animal. Sprint performance measured with a laser diode/photocell timed 'drag strip' is a new method employing new technology and is reported on in some detail. A second new test involves accelerating water past the fish at a constant rate in a traditional swim tunnel/respirometer. These two performance tests were designed to better understand the biology of a bentho-pelagic marine fish, the Atlantic cod (Gadus morhua). Finally, we report on a modified incremental velocity test that was developed to better understand the biology of the blacknose dace (Rhinichthys atratulus), a Nearctic, lotic cyprinid.

Acceleration↗
PubMed2003

Swimming of pregnant rats at different water temperatures.

We studied the chronic effect of exercise during water immersion, associated with thermal stress (water temperature at 22, 35 and 40 degrees C) at an intensity of 80% of maximal work load supported in pregnant rats (P) and non-pregnant female rats (NP). P and NP were subdivided into three subgroups according to water temperature during exercise (P22 and NP22; P35 and NP35; P40 and NP40). The animals were submitted to daily swimming sessions of 10-15 min, for 19 days of pregnancy (P) or experimental conditions (NP). Plasma concentration of triglycerides, cholesterol, glucose, total protein, albumin and corticosterone were determined 24 h after the last exercise session. Weight gain and rectal temperature pre- and post-swimming session were also determined. The offspring were examined just after caesarian section on the 20th day of pregnancy to check weight, length and litter size. Pregnant rats showed an increase of triglycerides, reduction of glycemia, total protein and albumin and cholesterol (at 35 degrees C) when compared to non-pregnant animals. Such effects probably lead to an adequate delivery of substrate to the fetus and prepare the mother for lactation. Daily thermal stress did not modify metabolic responses to exercise in pregnant rats. Results also show a deleterious effect on offspring when the mother is exposed daily to extreme temperatures during swimming. These results suggest that water temperature (cold and hot) in swimming have to be considered to avoid damage in fetal development.

Animals↗
PubMed1998

Swimming performance, venous oxygen tension and cardiac performance of coronary-ligated rainbow trout, Oncorhynchus mykiss, exposed to progressive hypoxia.

We performed in vivo studies to examine the idea that cardiac work is impaired in rainbow trout (Oncorhynchus mykiss) below a certain venous PO2 threshold. We hypothesized that coronary-ligated fish, swimming continuously at a reasonably high water velocity (1.5 body lengths x s(-1)) and exposed to progressive hypoxia, would fatigue at higher venous PO2 and ambient water PO2 compared with sham-operated fish. However, we found that both the lowest venous PO2 that supported hypoxic swimming (9.9 torr for coronary-ligated fish and 11.1 torr for sham-operated fish) and the venous PO2 at fatigue (7.8 torr and 8.6 torr, respectively) were the same for coronary-ligated and sham-operated fish. Also, both groups quit swimming at the same water PO2 heart rate and hematocrit. Nevertheless, significant differences in cardiac performance did exist between the two groups. Whereas ventral aortic blood pressure (Pva) increased significantly with hypoxic swimming in sham-operated fish, there was no such increase in coronary-ligated fish. In addition, cardiac arrhythmias occurred in coronary-ligated fish at fatigue, and these fish were slower to recover from exhaustion. We believe that the venous PO2 threshold to support cardiac performance in the absence of a coronary supply was between 7.8 and 9.9 torr. Furthermore, we suspect that the low PO2 in coronary-ligated fish effectively lowered their myocardial O2 demand. Uncertainty still exists regarding whether or not the venous PO2 threshold lies between 8.6 and 11.1 torr in sham-operated fish.

Animals↗
PubMed2003

Short- and long-term swimming exercise training increases myocardial insulin-like growth factor-I gene expression.

UNLABELLED: OBJECTIVES. We investigated the effect of short- and long-term swimming exercise, with or without insulin-like growth factor (IGF)-I administration, on the expression of myocardial IGFs and contractile proteins. METHODS: Sprague-Dawley male rats (n=36) were subjected to swimming exercise for 2 or 6 weeks. IGF-I (0.5mg/rat) was administered continuously for 1 week, using alzet osmotic pumps. Control groups remained sedentary. IGF-I, IGF-I receptor (IGF-IR), IGF-II, skeletal alpha-actin (sk-actin), and beta myosin heavy chain (beta MHC) mRNAs were measured using Northern blot analysis and RT-PCR. RESULTS: A significant 2-fold increase in myocardial IGF-I mRNA was found after 2 and 6 weeks of swimming in both IGF-I treated and untreated rats (p<0.001). IGF-IR mRNA was significantly (p<0.05) increased after 6 weeks of training only in the IGF-I treated animals. IGF-II mRNA remained unchanged at all time points. While beta MHC mRNA was significantly decreased (p=0.003) at 2 and 6 weeks, sk-actin mRNA remained unchanged. CONCLUSIONS: Short- and long-term swimming exercise training increase myocardial expression of IGF-I mRNA. Exogenous administration of IGF-I, during the first week of the exercise session, did not produce any effect on myocardial IGF-I but was associated with increased IGF-IR signal after the long-term exercise training. These data suggest a relationship between IGF-I expression and cardiac adaptation to exercise training.

Actins↗
PubMed2000

The effects of wet suits on physiological and biomechanical indices during swimming.

The objectives of this study were to verify the effects of wet suits (WS) on the performance during 1500m swimming (V1500), on the velocity corresponding to the anaerobic threshold (VAT) and on the drag force (AD) as well as its coefficient (Cx). 19 swimmers randomly completed the following protocols on different days (with and without WS): 1) maximal performance of 1500m swimming; 2) VAT in field test, with fixed concentration of blood lactate (4 mM) and 3) determination of hydrodynamic indices (AD and Cx). The results demonstrated significant differences (p < 0.05) in the VAT (1.27 +/- 0.09; 1.21 +/- 0.06 m.s-1), and in the V1500 (1.21 +/- 0.08; 1.17 +/- 0.08 m.s-1), with and without WS, respectively. However the AD, and its Cx did not present significant differences (p>0.05) for the respective maximal speeds of swimming. In summary, we can conclude that WS allows swimmers to reach greater speeds in both, long- and short-course swims. This improvement can be related to the decrease of the AD, since with higher speeds (with WS) the subjects presented the same resistance, as they did when compared to speeds without a WS. Moreover, these data suggest that the methodology used in this study to determine the Cx is unable to detect the improvement caused by WS.

Adult↗
PubMed1997

Benzodiazepine prevention of swim stress-induced sensitization of cortical biogenic amines: an in vivo microdialysis study.

In vivo microdialysis was used to determine the effect of diazepam, flumazenil and FG-7142 upon the biogenic amine response to acute and repeated swim stress in the medial prefrontal cortex of the rat. Acute swim stress increased norepinephrine levels, although dopamine and serotonin levels remained stable. Upon re-exposure to swim stress twenty-four hours later, sustained increases (200-300% of baseline) in all three biogenic amines were detected. This enhanced response to re-stress was not seen in rats pretreated with either a benzodiazepine: agonist (diazepam, 2 mg/kg), an antagonist (flumazenil, 10 mg/kg), or an inverse agonist (FG-7142, 10 mg/kg) given prior to the first swim stress. Therefore, the sensitization of biogenic amine response to re-stress may be prevented by compounds which differ in their activity at the benzodiazepine receptor.

Animals↗
PubMed1991

Effects of corticosterone on response consolidation and retrieval in the forced swim test.

In the forced swimming test, adrenal hormones regulate immobility time during a test swim given 24 hr after the initial training swim (e.g., the deficit in adrenalectomized animals is reduced when animals are given corticosterone [B] immediately after the training session). In this study, adrenalectomy decreased and B restored immobility during the test swims. The effects of adrenalectomy were completely reversed by 1 mg/kg doses of B, which results in plasma B levels that are comparable to values under basal resting conditions. Higher doses of B had no further effect. B given before or immediately after training partially reversed the effects of adrenalectomy. The complete reversal of the effects of adrenalectomy, however, required the presence of B during both training and testing, suggesting that B plays a role in the consolidation-retention and retrieval of the immobility response.

Adrenalectomy↗
PubMed2000

Comparison of critical swimming velocity and velocity at lactate threshold in elite triathletes.

The purpose of this study was to determine whether the critical swimming velocity (Vcrit) corresponds to the velocity at lactate threshold (V-LT) in elite triathletes. Eight elite triathletes (5 male, 3 female; age 26 +/- 4 years; height 1.7 +/- 0.1 m and body mass 75 +/- 4 kg) participated in the study. Vcrit, defined as the speed that could theoretically be maintained indefinitely without exhaustion, was expressed as the slope of a regression line between swimming distance covered and the corresponding times of five time trials over 100, 200, 400, 800 and 1500m and all combinations of these. Lactate threshold (LT) was determined by visual inspection as the point of first inflection of the lactate-work rate curve following 5 x 300 m swims of increasing velocity which were paced using the Aquapacer (Challenge and Response, Inverurie, Scotland). Velocities of the 300 m swims were -10, -5, 0, +5 and +10% of the average 100m pace from a 1500 m time trial. Vcrit was similar regardless of the combination or number of time trials used in the linear regression. For all subjects Vcrit was significantly faster (p <0.05) than V-LT (1.23 +/- 0.11 m x s(-1) and 1.15 +/- 0.10 m x s(-1) respectively). Blood lactate concentrations were also significantly higher (p < 0.05) at Vcrit (3.0 +/- 1.0 mM) than at LT (1.9 +/- 0.4 mM). Results from the present study demonstrate that Vcrit can be calculated from any two time trials in triathletes, however Vcrit did not represent V-LT in triathletes. Since Vcrit is faster than V-LT it is unlikely to be sustained indefinitely and consequently the notion of Vcrit should be re-evaluated in light of these findings.

Adult↗
PubMed2006

[Swimming pool lung -- extrinsic allergic alveolitis or mycobacterial disease?].

There have been several recent reports of pulmonary disease resulting from exposure to Mycobacterium avium complex in indoor hot tubs. The disease is thought to be due either to infection or extrinsic allergic alveolitis (EAA). In this report we describe the case of a patient who developed episodes of fever, dyspnea and cough 4-6 hours after cleaning his indoor swimming pool. A diagnosis of EAA was made on finding a restrictive lung function pattern with gas exchange abnormalities, a predominant lymphocytosis in the bronchoalveolar lavage, diffuse ground-glass opacities in the lower lobes on high-resolution computer tomography, and specific IgG antibody activity to the swimming pool water. There was no precipitin reaction or specific IgG antibody activity to microbes extracted from the water. Interestingly, the water contained Mycobacterium avium complex (MAC) in huge amounts and in this case the histopathological features of the lung biopsy specimens differed from those seen in typical EAA, but were similar to those described in "hot tub lung" caused by mycobacteria. Solely by avoidance of cleaning the swimming pool, without any pharmacological treatment, the patient recovered completely within three months. To the best of our knowledge, this is the first report of EAA possibly associated with MAC exposure in a swimming pool environment.

Adult↗
PubMed1986

Noninvasive determination of the anaerobic threshold in swimming.

The relationship between swimming velocity (V) and heart rate (HR) was determined in 60 swimmers. The athletes were asked to increase their work intensity progressively, from low to submaximal velocities; HRs were determined by a telemetric cardiofrequency meter. In all the athletes examined and for each style employed, the linearity of the V3-HR relationship was maintained up to a submaximal velocity (deflection velocity, Vd), beyond which the increase in work intensity exceeded the increase in HR. The test-retest correlation for Vd determined in nine pent-athletes was 0.99. Vd and anaerobic threshold (AT), determined through lactate measurements, were correlated in six swimmers (r = 0.84). Vd and average swimming velocities in a modern pentathlon swimming race (300 m free-style) were also correlated (n = 9, r = 0.91), thus suggesting that AT is critical in determining the speed in middle-distance swimming events.

Adult↗
PubMed1984

Proteinuria in intact and splenectomized dogs after running and swimming.

The occurrence of post-exercise proteinuria was investigated in intact and splenectomized dogs after treadmill running and swimming and compared to control experiments. Albumin and lysozyme were measured by radial diffusion. Urinary protein was analyzed by SDS-polyacrylamide gel electrophoresis. Swimming in the splenectomized dogs increased the albumin excretion in the first 30 min after exercise from 0.03 to 0.22 mg X min-1 and the lysozyme excretion in the same period from 0.11 to 0.75 micrograms X min-1. Swimming in intact dogs caused smaller increase in the lysozyme and albumin excretions during the exercise period itself as well as in the albumin excretion in the first 30 min after exercise. Running had no effect on urinary albumin or lysozyme but increased the low molecular weight protein fraction in the splenectomized dogs. Plasma lactate concentrations were higher during swimming in the splenectomized dogs than in the intact dogs. Possible mechanisms of post-exercise proteinuria are discussed.

Animals↗
PubMed1998

Estrogen alters behavior and forebrain c-fos expression in ovariectomized rats subjected to the forced swim test.

Estrogen has been implicated in brain functions related to affective state, including hormone-related affective disorders in women. Although some reports suggest that estrogen appears to decrease vulnerability to affective disorders in certain cases, the mechanisms involved are unknown. We used the forced swim test (FST), a paradigm used to test the efficacy of antidepressants, and addressed the hypotheses that estrogen alters behavior of ovariectomized rats in the FST and the FST-induced expression of c-fos, a marker for neuronal activity, in the rat forebrain. The behaviors displayed included struggling, swimming, and immobility. One hour after the beginning of the test on day 2, the animals were perfused, and the brains were processed for c-fos immunocytochemistry. On day 1, the estradiol benzoate-treated animals spent significantly less time struggling and virtually no time in immobility and spent most of the time swimming. Control rats spent significantly more time struggling or being immobile during a comparable period. On day 2, similar behavioral patterns with still more pronounced differences were observed between estradiol benzoate and ovariectomized control groups in struggling, immobility, and swimming. Analysis of the mean number of c-fos immunoreactive cell nuclei showed a significant reduction in the estradiol benzoate versus control groups in areas of the forebrain relating to sensory, contextual, and integrative processing. Our results suggest that estrogen-induced neurochemical changes in forebrain neurons may translate into an altered behavioral output in the affective domain.

Animals↗