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PubMed1991

Swimming navigation and structural variations of the infrapyramidal mossy fibers in the hippocampus of the mouse.

The extent of the infrapyramidal mossy fiber projection in CA3 (IIP-MF) at the midseptotemporal level correlates negatively with two-way avoidance learning and positively with performance in the radial maze, both tasks known to be sensitive to hippocampal lesions. If hippocampal structural variations are causing behavioral variations, one must predict positive correlations between the extent of the IIP-MF and performance in swimming navigation. Thus, the authors studied learning and reversal learning of swimming navigation in mice in which the size of the IIP-MF had been randomized by means of systematic crosses and in 2 mouse strains known for differential infrapyramidal projections (C57BL/6 and DBA/2). In 19 random-bred mice (9 male, 10 female), the extent of the IIP-MF showed negative correlations with swimming time after platform reversal (day 4: r = -0.50, P < .03; day 5 r = -0.73, P < .001), but none during acquisition of the task. In addition, statistical analysis suggested an influence of asymmetrically distributed mossy fiber projections during reversal learning. The strain comparison between 18 DBA/2 and 16 C57BL/6 male mice confirmed these results: no strain difference during days 1-3, and a significantly faster swimming time in the strain C57BL/6 (with large IIP-MF) at day 5 (second day of reversal), associated with significantly more crossings of the former platform location during the early phases of reversal learning. This latter measure was also negatively correlated with asymmetry of the IIP-MF in both strains. Finally, variations of the IIP-MF were correlated partially with adjustment of swimming speed that appeared to depend on size and asymmetry of CA4 as well. Thus, natural variations in the size of the IIP-MF distribution, and, perhaps, of CA4, appear to linearly influence processes directly involved in complex spatial learning.

Animals↗
PubMed2001

Thyroxine induces transitions in red muscle kinetics and steady swimming kinematics in rainbow trout (Oncorhynchus mykiss).

During normal development, rainbow trout undergo a shift in red muscle contraction kinetics and swimming kinematics. Young trout parr have faster muscle kinetics and faster tailbeat frequency during swimming than older, larger juvenile trout. In this study, the thyroid hormone thyroxine (T(4)) was used to induce these changes in trout parr. This allowed a comparison of swimming kinematics, through the use of video analysis and electromyography, and red muscle contractile properties, through the use of in vitro muscle preparations, between natural parr and same-sized induced juveniles. The red muscle of natural parr has faster contractile properties than induced juveniles, including faster twitch time and a faster maximum shortening velocity (V(max)). Further, natural parr swim with faster tailbeat frequencies than induced juveniles. The results suggest that the natural shift in red muscle contraction kinetics observed during parr-smolt transfomation in trout directly affects swimming behavior in these fish. Also, thyroid hormones appear to induce a shift towards slower isoforms of the muscle protein myosin heavy chain (MHC), a result distinct from work on rats where thyroid hormones induce shifts towards faster forms of MHC. J. Exp. Zool. 290:115-124, 2001.

Animals↗
PubMed1997

Repeated cold water swim produces delayed nociceptive responses, but not analgesia, for tonic pain in the rat.

Earlier studies have demonstrated that cold water swim (CWS) produces stress-induced analgesia in tests of brief, phasic pain and produces a delayed nociceptive response (DNR) for more prolonged tonic pain. The present study reports the effect of repeated CWS on tonic pain, as measured by the formalin test. One group of rats was exposed to a 3.5-min swim in 2 degrees C water immediately prior to the formalin injection, to a 1.5-min swim at 50 min, and to another 1.5-min swim at 100 min postformalin injection. Compared to the no-swim control group, subjects which received repeated CWS had dramatically altered formalin pain responses. Formalin responses began just over 3 h postformalin injection, peaked at 4 h, and were still present at 5 h. Inspection of individual responses revealed a substantial degree of variability in the onset of responses, although the magnitude and duration of the formalin pain response remained at the same levels as those of control subjects. The lack of a decrease in the magnitude and duration of the delayed formalin responses indicates that repeated CWS does not produce analgesia for tonic pain. The period of stress, therefore, produces pain suppression but not loss of the mechanisms that subsequently underlie the pain. Earlier controls have ruled out peripheral mechanisms (such as retention of the formalin in the paw tissue). Rather, a memory mechanism appears to have been indicated and it is not lost, but persists until it can be manifested. Further research is needed to study the mechanisms responsible for the DNR.

Analgesia↗
PubMed1996

Composition of the excitatory drive during swimming in two amphibian embryos: Rana and Bufo.

It has recently been shown that spinal neurons in Xenopus embryos receive cholinergic and electrotonic excitation during swimming, in addition to the well documented excitatory amino acid (EAA)-mediated excitation. We have now examined the composition of the excitatory drive during swimming in embryos of two further amphibian species, Rana and Bufo, which have somewhat different motor patterns. Localised applications of antagonists show that presumed motoneurons in Rana and Bufo embryos receive both cholinergic and FAA input during swimming. There is also a further chemical component which is blocked by Cd2+ and a small Cd(2+)-insensitive component, which is usually non-rhythmic. Rhythmic Cd(2+)-insensitive components, presumed to be phasic electrotonic potentials, were only seen in a small proportion of Bufo neurons and in no Rana neurons. While EAA and cholinergic inputs therefore appear to be consistent features of excitatory drive for swimming in amphibian embryo motoneurons, electrotonic input apparently occurs less commonly. Antagonist specificity was tested using applied agonists in Rana. Results of these tests also suggested that the further, unidentified Cd(2+)-sensitive component seen during swimming could represent an incomplete block of AMPA receptor-mediated excitation.

Animals↗
PubMed1994

Effects of strychnine on fictive swimming in the lamprey: evidence for glycinergic inhibition, discrepancies with model predictions, and novel modulatory rhythms.

1. Inhibitory postsynaptic potentials (ipsps) produced by two classes of interneurons, CC (Contralateral and caudal projecting) and lateral interneurons, were tested for strychnine sensitivity using paired intracellular recordings in the lamprey spinal cord. The ipsps were partially blocked by 0.2-0.5 microM strychnine and were completely blocked by 5 microM strychnine. Thus, the ipsps may be glycinergic. 2. These interneurons are key participants in a proposed circuit model for fictive swimming. A connectionist-type computer simulation of the model demonstrated that the cycle period of the network increased with decreasing ipsp strength. 3. Application of strychnine (0.1-0.5 microM) to the spinal cord during fictive swimming induced by an excitatory amino acid increased cycle period, consistent with previous reports, but at odds with stimulation predictions. 4. Strychnine also produced slow rhythmic modulation of fictive swimming (period = 12 s) which maintained left-right alternation and rostral-caudal coordination. Auto- and cross-correlation analyses revealed that the slow modulation was present in a weaker form in most control preparations during fictive swimming. 5. Since the proposed model for the swimming pattern generator in the lamprey spinal cord does not predict the observed speeding with strychnine, nor the slow modulatory rhythm, it appears to be deficient in its present formulation.

Animals↗
PubMed1983

Plasma volume changes during submaximal swimming.

The hemodynamic and diuretic responses of six swimmers were evaluated during 35 min of resting immersion, free swimming, and land bicycle ergometry at approximately 70% exercise specific maximal oxygen uptake. Venous blood, sampled at 0, 5, 10, 15, 25, and 35 min of each trials, was analyzed for hemoglobin. hematocrit, and total plasma protein concentration. Urine output was also measured. Resting immersion resulted in a significant (p less than 0.05) hemodilution (plasma volume = +2.5 +/- 1.5%) during the first 25 min and a return towards resting levels at the termination. During swimming exercise, plasma volume decreased by -15.9 +/- 1.3% (p less than 0.01). A similar -17.0 +/- 1.3% decrease was also evident during cycle ergometry. Urine output averaged 3.1 +/- 0.9 ml x min-1 during resting immersion, significantly greater than either swimming (1.0 +/- 0.1 ml x min-1) or cycling (0.4 +/- 0.2 ml x min-1). Total plasma protein concentration increased less during cycling compared to swimming (p less than 0.05) and was unchanged (p greater than 0.05) during resting immersion. It was concluded that the hemodynamic and renal responses to immersion are suppressed during swimming. It was also apparent that, despite possible differences in hemodynamics, plasma shift during exercise may be similar on land and in the water. It appears that the amount of plasma lost from the intravascular space during exercise may be independent of the muscle mass involved, but related to a combination of the ratio of active to total mass for each individual and body position.

Adult↗
PubMed1987

Respiratory valve for oxygen uptake measurements during swimming.

A detailed description of a respiratory valve to measure oxygen uptake while swimming is given. The effect on body drag of the addition of this equipment was measured in four subjects swimming over a range of speeds (0.9-1.9 m s-1). The respiratory valve has a low airflow resistance (29 Pa at an airflow of 8 l X s-1) and a small deadspace (30 ml). Total body drag when swimming while wearing the respiratory equipment did not differ significantly from that when swimming without the equipment. It is concluded that this respiratory valve is ideal for making valid and reliable measurements of oxygen uptake during swimming.

Evaluation Studies as Topic↗
PubMed1988

Neither the pituitary gland nor the sympathetic nervous system is responsible for eliciting the large drop in elevated rat pineal melatonin levels due to swimming.

Since the pineal gland is an end organ of the sympathetic nervous system, stress might increase the synthesis of its hormone, melatonin. The stress of a 10 min swim, which elicits a marked rise in circulating catecholamines, causes a dramatic depression of high pineal melatonin levels at night within 15 min after swimming onset. N-acetyltransferase (NAT) activity is unaffected by the treatment at 15 or 30 min after swimming onset. Within 90 min after initiation of a 15 min swim, high nighttime pineal melatonin levels are restored while NAT values remain elevated. The swimming-induced reduction in high pineal melatonin levels is not influenced by either hypophysectomy, superior cervical ganglionectomy, prazosin (alpha 1-adrenergic receptor blocker) pretreatment, yohimbine (alpha 2-adrenergic receptor blocker) pretreatment, or reserpine (amine depletor) pretreatment. These results indicate that neither hormones secreted from the pituitary gland nor catecholamines secreted from the sympathetic nerves are involved in eliciting the dramatic reduction in elevated pineal melatonin levels in the rat.

Animals↗
PubMed1991

Role of genotype and dopamine receptors in behaviour of inbred mice in a forced swimming test.

The role of genotype in the effects of selective D1 and D2 dopamine agonists and antagonists on behavioural despair (Porsolt's test) was studied. Mice of nine inbred strains showed significant interstrain differences in duration of immobility. The influence of dopaminergic drugs was assessed in six strains characterized by different levels of swimming activity. SKF 38393 (10 mg/kg), an agonist at D1 dopamine receptors, increased swimming activity, while the D1 antagonist SCH 23390 (0.2 and 0.5 mg/kg) reduced it, the effects being genotype dependent. The involvement of D2 dopamine receptors in the regulation of mouse behaviour in the forced swimming test was not so evident; the D2 agonist bromocriptine (10 mg/kg) produced no significant effect. The D2 agonist quinpirole (2.5 mg/kg) increased immobility in the majority of the mouse strains studied, while in CBA mice it resulted in a marked reduction of immobility. The D2 antagonist sulpiride (20 mg/kg) decreased immobility and increased active swimming only in two strains. The present results suggest a different role for D1 and D2 dopamine receptors in the regulation of swimming in the mouse.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1994

Chronic variable stress or chronic morphine facilitates immobility in a forced swim test: reversal by naloxone.

The behaviors displayed in a forced swim test were investigated in rats previously exposed to a chronic variable stress treatment or chronic administration of morphine. In addition, to further explore the participation of an endogenous opiate mechanism in these behavioral effects, naloxone was either administered during the chronic treatment (prior to each stress or morphine exposure) or immediately prior to the forced swim test. Animals were submitted daily to a different stressor for 1 week or injected with morphine (10 mg/kg, IP) for 6 days, whereas controls were unmanipulated except for the injection process. On the day following the last stressor, control and stressed animals were administered saline or naloxone (2 mg/kg, IP) 15 min prior to the forced swim test. Morphine treated animals were similarly tested on the third day following the last morphine injection. In a separate group of rats, naloxone (2 mg/kg, IP) was administered daily 10 min prior to each stressor of the chronic stress regime or each daily morphine injection. A significant increase in the time spent in immobility was observed in stressed animals as well as in rats chronically treated with morphine. In both groups, this potentiated immobility was attenuated by naloxone pretreatment prior to the forced swim test or when given before each daily stressor or morphine injection. In addition, the concurrent exposure to stress or morphine along with naloxone administration enhanced struggling in the first 5 min of the forced swim test.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Renal hemodynamics and proteinuria in running and swimming beagle dogs.

In beagle dogs swimming, in contrast to treadmill running, was found to cause an increase in urine flow and urinary protein excretion. Renal blood flow measured by electromagnetic flow probes decreased by 13.0 +/- 4.9% when the treadmill gradient was 15% and arterial pressure was elevated by 11.6 +/- 4.9%. Immersion resulted in an immediate decrease in renal blood flow of 8.8 +/- 5.1% and a 24.6 +/- 6.9% increase in arterial pressure. Acid-base status indicated a respiratory alkalosis in all running experiments, no net change in five swimming experiments in which hyperventilation occurred, but a metabolic acidosis in eight swimming experiments without hyperventilation. During running there was a threefold increase in oxygen consumption. We conclude that swimming possibly induces more sympathetic nervous activity than treadmill running in dogs, while an alkalosis is consistently present during running, but acid-base response is variable during swimming.

Acid-Base Equilibrium↗
PubMed2005

Differential behavioral effects of the antidepressants reboxetine, fluoxetine, and moclobemide in a modified forced swim test following chronic treatment.

RATIONALE: The forced swim test (FST) is the most widely used model for assessing potential antidepressant activity in rodents following acute or short-term treatment. However, few studies have compared the effects of short- and long-term antidepressant treatment on behaviors in the test, despite the need to treat patients chronically to produce clinical effects. OBJECTIVES: The current studies examined whether antidepressants from different classes produce different behavioral effects following short-term treatment and whether such effects change following administration for a longer duration. METHODS: The effects of administering short-term (3 days) and long-term (14 days) treatments of antidepressants from three different chemical classes with distinct mechanisms of action via osmotic minipump were examined: the selective norepinephrine reuptake inhibitor reboxetine (10 and 60 mg kg(-1) day(-1)), the selective serotonin reuptake inhibitor fluoxetine (2.5 and 15 mg kg(-1) day(-1)), and the reversible inhibitor of monoamine oxidase moclobemide (2.5 and 15 mg kg(-1) day(-1)). All testing was carried out in a 15-min test with no preswim session in order to negate any confounding aspect of an induction procedure. RESULTS: The majority of antidepressant-sensitive behavioral changes were observed in the first 5 min of the test. The low dose of reboxetine failed to alter behavior in the test after 3 days but significantly decreased immobility and increased climbing behavior following administration for 14 days, whereas the high dose of reboxetine was equally effective following 3 and 14 days of treatment. In a similar fashion, the low dose of fluoxetine failed to alter behavior in the test following 3 days, but showed an augmented response on immobility and increased swimming following administration for 14 days. The high dose of fluoxetine was slightly more effective at reducing immobility following administration for 14 days than 3 days. The low dose of moclobemide decreased immobility and increased climbing behavior following treatment for 3 days, but increases in both swimming and climbing behaviors were measured following treatment for 14 days. Treatment with the high dose of moclobemide for 3 days decreased immobility and increased swimming, whereas treatment for 14 days significantly increased both active behaviors (swimming and climbing). CONCLUSIONS: Antidepressants from three different classes produce different effects on active behaviors in the FST. The effects of antidepressants were augmented following chronic administration for 14 days, especially when given at low doses. This suggests that modifications of the FST can be used to examine the onset of action of antidepressant agents produced by long-term administration.

Animals↗
PubMed2006

An elastic rod model for anguilliform swimming.

We develop a model for anguilliform (eel-like) swimming as an elastic rod actuated via time-dependent intrinsic curvature and subject to hydrodynamic drag forces, the latter as proposed by Taylor (in Proc Roy Proc Lond A 214:158-183, 1952). We employ a eometrically exact theory and discretize the resulting nonlinear partial differential evolution both to perform numerical simulations, and to compare with previous models consisting of chains of rigid links or masses connected by springs, dampers, and prescribed force generators representing muscles. We show that muscle activations driven by motoneuronal spike trains via calcium dynamics produce intrinsic curvatures corresponding to near-sinusoidal body shapes in longitudinally-uniform rods, but that passive elasticity causes Taylor's assumption of prescribed shape to fail, leading to time-periodic motions and lower speeds than those predicted Taylor (in Proc Roy Proc Lond A 214:158-183, 1952). We investigate the effects of bending stiffness, body geometry, and activation patterns on swimming speed, turning behavior, and acceleration to steady swimming. We show that laterally-uniform activation yields stable straight swimming and laterally differential activation levels lead to stable turns, and we argue that tapered bodies with reduced caudal (tail-end) activation (to produce uniform intrinsic curvature) swim faster than ones with uniform activation.

Animals↗
PubMed2002

Motor program initiation and selection in crickets, with special reference to swimming and flying behavior.

An air puff stimulus to the cerci of a cricket (Gryllus bimaculatus) evokes flying when it is suspended in air, while the same stimulus evokes swimming when it is placed on the water surface. After bilateral dissection of the connectives between the suboesophageal and the prothoracic ganglia or between the brain and the suboesophageal ganglion, the air puff stimulus evokes flying even when the operated cricket is placed on the water surface. A touch stimulus on the body surface of crickets placed on the water surface elicits only flying when the connectives between suboesophageal and prothoracic ganglia are dissected, while the same stimulus elicits either swimming or flying when the connectives between the brain and the suboesophageal ganglion are dissected. These results suggest that certain neurons running through the ventral nerve cords between the brain and the suboesophageal ganglion or between the suboesophageal and the prothoracic ganglia play important but different roles in the initiation and/or switching of swimming and flying. In the suboesophageal ganglion, we physiologically and morphologically identified four types of "swimming initiating neurons". Depolarization of any one of these neurons resulted in synchronized activities of paired legs with a similar temporal sequence to that observed during swimming.

Air Movements↗
PubMed2002

Both shared and specialized spinal circuitry for scratching and swimming in turtles.

In principle, nervous systems could generate a behavior either via neurons that are relatively specialized for producing one behavior or via multifunctional neurons that are shared among multiple, diverse behaviors. I recorded extracellularly from individual turtle spinal cord neurons while evoking hindlimb scratching, swimming, and withdrawal motor patterns. The majority of spinal neurons recorded were activated during both scratching and swimming motor patterns, consistent with the existence of shared circuitry for these types of limb movements. These neurons tended to have a similar degree of rhythmic modulation of their firing rate and a similar phase preference within the hip flexor activity cycle during scratching and swimming motor patterns. In addition, a substantial minority of neurons were activated during scratching motor patterns but silenced during swimming motor patterns. This raises the possibility that inhibitory interactions between some scratching and swimming neural circuitry play a role in motor pattern selection. These scratch-specialized neurons were also less likely than the putative shared neurons to be activated during withdrawal motor patterns. Thus, these neurons may represent two separate classes, one of which is used generally for hindlimb motor control and the other of which is relatively specialized for a subset of hindlimb movement types.

Action Potentials↗
PubMed2002

The neuronal targets for GABAergic reticulospinal inhibition that stops swimming in hatchling frog tadpoles.

In most animals locomotion can be started and stopped by specific sensory cues. We are using a simple vertebrate, the hatchling Xenopus tadpole, to study a neuronal pathway that turns off locomotion. In the tadpole, swimming stops when the head contacts solid objects or the water's surface meniscus. The primary sensory neurons are in the trigeminal ganglion and directly excite inhibitory reticulospinal neurons in the hindbrain. These project axons into the spinal cord and release GABA to inhibit spinal neurons and stop swimming. We ask whether there is specificity in the types of spinal neuron inhibited. We used single-neuron recording to determine which classes of spinal neurons receive inhibition when the head skin is pressed. Ventral motoneurons and premotor interneurons involved in generating the swimming rhythm receive reliable GABAergic inhibition. More dorsal inhibitory premotor interneurons are inhibited less reliably and some are excited. Dorsal sensory pathway interneurons that start swimming following a touch to the trunk skin do not appear to receive such inhibition. There is therefore specificity in the formation of descending inhibitory connections so that more ventral neurons producing swimming are most strongly inhibited.

Animals↗
PubMed2005

Development of swimming in the medicinal leech, the gradual acquisition of a behavior.

Observing the development of behavior provides an assay for the developmental state of an embryo's nervous system. We have previously described the development of behaviors that were largely confined to one or a few segments. We now extend the work to a kinematic analysis of the development of swimming, a behavior that requires coordination of the entire body. When leech embryos first begin to swim they make little forward progress, but within several days they swim as effectively as adults. This increase in efficacy depends on changes in body shape and on improved intersegmental coordination of the swim central pattern generator. These kinematic details suggest how the swim central pattern generating circuit is assembled during embryogenesis.

Age Factors↗
PubMed1998

Assessing the roles of glutamatergic and cholinergic synaptic drive in the control of fictive swimming frequency in young Xenopus tadpoles.

This paper investigates the proposal that the frequency of the swimming central pattern generator in young Xenopus tadpoles is partly determined by the population of glutamatergic premotor interneurons active on each cycle. During fictive swimming spinal neurons also receive cholinergic and electrotonic excitation from motoneurons. As frequency changes during swimming we make two predictions: first, since most motoneurons fire very reliably at all frequencies, the electrotonic and nicotinic drive from motoneurons should remain constant, and second, when swimming frequency decreases, the glutamatergic drive should decrease as the number of active premotor excitatory interneurons decreases. We have tested these predictions by measuring the excitatory synaptic drive to motoneurons as frequency changes during fictive swimming. The components of synaptic drive were revealed by the local microperfusion of strychnine together with different excitatory antagonists. After blocking the nicotinic acetylcholine receptor, the mainly glutamatergic excitatory synaptic drive still changed with frequency. However, when glutamate receptors or all chemical transmission was blocked, excitation did not change with frequency. Our predictions are confirmed, suggesting that premotor excitatory interneurons are a major factor in frequency control in the tadpole central pattern generator and that motoneurons provide a stable background excitation.

Animals↗