Maze-escape learning and memory during rat ontogeny

With the method of a simple automatic rectangular maze the development of escape reaction was studied in albino rats aged 3 weeks to 3 months as well as memory retrieval within 24 h and then after one month. Learning of escape improves sharply between the 3rd and 4th postnatal week, and then, with the exception of week 8, remains approximately on the same level. Memory retrieval up to 24 h is not significantly influenced by age or sex, but is best immediately after learning interval of 10 min and the poorest after 24 h, except the age of 5 weeks, where it is best in 3 and 6 h after learning. One-month retention of maze escape improves during development except in animals trained at the age of 6 weeks in which the level is lower than in all other investigated groups. One-month memory retrieval in animals taught at the age of 4 weeks is influenced by the time of the first retention test with the best values in animals tested for the first time after 3 h and poorest in animals tested after 24 h after learning. Animals trained at 5 weeks had a marginally better result after the one-month retention test in females, perhaps due to the influence of sexual maturation on memory traces. This was not observed in the other age groups. Attention is drawn to the different development of learning and memory of various types of conditioned reactions stemming from the difference in their complexity.     

Japanese Quail’s Genetic Background Modulates Effects of Chronic Stress on Emotional Reactivity but Not Spatial Learning

Chronic stress is known to enhance mammals’ emotional reactivity and alters several of their cognitive functions, especially spatial learning. Few studies have investigated such effects in birds. We investigated the impact of a two-week stress on Japanese quail’s emotional reactivity and spatial learning. Quail is an avian model widely used in laboratory studies and for extrapolation of data to other poultry species. As sensitivity to chronic stress can be modulated by intrinsic factors, we tested juvenile female Japanese quail from three lines, two of them divergently selected on tonic immobility duration, an indicator of general fearfulness. The different emotional reactivity levels of quail belonging to these lines can be revealed by a large variety of tests. Half of the birds were submitted to repeated unpredictable aversive events for two weeks, whereas the other half were left undisturbed. After this procedure, two tests (open field and emergence tests) evaluated the emotional reactivity of treated and control quails. They were then trained in a T-maze for seven days and their spatial learning was tested. The chronic stress protocol had an impact on resting, preening and foraging in the home cage. As predicted, the emotional reactivity of treated quails, especially those selected for long tonic immobility duration, was higher. Our spatial learning data showed that the treatment enhanced acquisition but not memorization. However, intrinsic fearfulness did not seem to interact with the treatment in this test. According to an inverted U-shaped relationship between stress and cognition, chronic stress can improve the adaptability of birds to a stressful environment. We discussed the mechanisms possibly implied in the increase of emotional reactivity and spatial abilities.     

Effects of repetitive exercise on neonatal rat skeletal muscle oxidative capacity

Since little is known about the training response to exercise in neonatal animals, this study was undertaken to elucidate the potential of oxidative system adaptations in developing skeletal muscle of rats during 50 days of daily treadmill running. The training regimen involved male and female rats (10 days old) initially running 0.1 mph, 0% grade, for 15 min. The program progressed to 1 mph, 25% grade, for 60 min by 50 days of age. At 25 days of age, pyruvate and palmitate oxidative capacity, and citrate synthase activity in red vastus muscle homogenates were elevated in the trained group (T) compared with age- and sex-matched controls (C). These increases were also observed for each subsequent time point tested and occurred in spite of the fact that the peak oxidative capacity of neonatal red vastus muscle was 46% greater than adult values. Further, trained animals tested at 45 days of age responded with a 12% increase in maximal oxygen consumption (Vo2max) compared with controls (P less than 0.05). Assays of muscle phosphofructokinase and of creatine phosphokinase activity conducted at this time point revealed no difference between T and C groups. Collectively, these data suggest that neonatal rats can be successfully trained and that they respond to an endurance-type program qualitatively similarly to adult rats.     

The 50s Cliff: A Decline in Perceptuo-Motor Learning,Not a Deficit in Visual Motion Perception

Previously, we measured perceptuo-motor learning rates across the lifespan and found a sudden drop in learning rates between ages 50 and 60, called the “50s cliff.” The task was a unimanual visual rhythmic coordination task in which participants used a joystick to oscillate one dot in a display in coordination with another dot oscillated by a computer. Participants learned to produce a coordination with a 90° relative phase relation between the dots. Learning rates for participants over 60 were half those of younger participants. Given existing evidence for visual motion perception deficits in people over 60 and the role of visual motion perception in the coordination task, it remained unclear whether the 50s cliff reflected onset of this deficit or a genuine decline in perceptuo-motor learning. The current work addressed this question. Two groups of 12 participants in each of four age ranges (20s, 50s, 60s, 70s) learned to perform a bimanual coordination of 90° relative phase. One group trained with only haptic information and the other group with both haptic and visual information about relative phase. Both groups were tested in both information conditions at baseline and post-test. If the 50s cliff was caused by an age dependent deficit in visual motion perception, then older participants in the visual group should have exhibited less learning than those in the haptic group, which should not exhibit the 50s cliff, and older participants in both groups should have performed less well when tested with visual information. Neither of these expectations was confirmed by the results, so we concluded that the 50s cliff reflects a genuine decline in perceptuo-motor learning with aging, not the onset of a deficit in visual motion perception.     

Species, population and age diversity in cell resistance to adhesion of Neisseria meningitidis serogroups A, B and C

The variation of cell adherence of meningococci serogroups A, B and C and influenza viruses was investigated in 11 animal species and in humans of different age groups (1st, 2nd, 3rd and 4th weeks; 2nd-3rd months; 4th-12th months, 2nd-3rd years; and 18th-60th years of life) as well as in women during pregnancy (17th-36th weeks) and childbirth. Red blood cells of all animals tested as well as of human newborns were absolutely resistant to attachment of meningococci. In neonatal and the later periods the human cells become far differently sensitive individually to meningococcal adhesion. In contrast, the viral adhesion was characterized by different individual cell sensitivity in all age groups tested. Pregnancy and childbirth did not influence the women's cell sensitivity to adhesion of Neisseria meningitidis. Different receptors are involved in interactions of human cells with influenza viruses and meningococci. The function of meningococcal receptors on human cells develops during postnatal ontogenesis. The variations express both specific (genetic) and ontogenetic (individual) differences in natural resistance to meningococcal infection.     

Strain-independent global effect of hippocampal proteins in mice trained in the Morris water maze

A series of individual proteins have been linked to performance in the Morris water maze (MWM) but no global effects have been reported. It was therefore the aim of the study to show which proteins were strain-independent, global factors for training in the MWM. Strains C57BL/6J, apodemus sylvaticus and PWD/PhJ were used. MWM and gels from trained animals were from a previous own study and corresponding yoked groups were generated. Hippocampal proteins were extracted and run on two-dimensional gel electrophoresis. Spots with different expressional levels between trained and yoked groups were punched and identified by mass spectrometry (nano-LC-ESI-MS/MS, ion trap). Two-way ANOVA with two factors (strain and training) was carried out and a Bonferroni test was used to compare groups. 12 proteins from several pathways and cascades showed different levels in trained mice versus corresponding yoked animals in all strains tested. Four out of these proteins were verified by immunoblotting: beta-synuclein, profilin 2, nucleoside diphosphate kinase A (NME1) and isocitrate dehydrogenase 3. Four proteins verified by immunoblotting could be shown to be involved in training in the MWM as a global effect, independent of the strain tested.     

Die Auswirkung der Übungsverteilung auf das Lernen und Vergessen bei Carassius auratus auratus Linné3

The significance of massed and distributed practice in discrimination learning to criterion by goldfish was studied. All animals were trained to discriminate between 6 horizontal black and white stripes (positive stimulus) and 2 vertical black and white stripes (negative stimulus). 5 groups of animals, 12 Ss each, got different training programs. Groups varied in number of trials per day (30, 10, 5 successive trials) and in distribution of trials over the day (30 trials given in blocks of 5 with ITI of 1 h or 5 trials, each spaced by an ITI of 1 h). In general animals with a small number of massed trials/day were superior in early acquisition period. When trials/day were spaced the method proved to be more efficient. The training method showed no effect concerning retention.     

Estimating the requirement of dietary crude protein for growing blue-breasted quail (Excalfactoria chinensis)

Two experiments were conducted to investigate the requirement for dietary crude protein (CP) in growing blue-breasted quail (BBQ). In Experiment 1, 300 1-day-old quails were randomly assigned to 10 groups according to a 2×5 factorial arrangement of treatments with two metabolisable energy (ME) levels (12.13 and 13.39 MJ/kg) and five CP concentrations (160, 190, 220, 250 and 280 g/kg) for 8 weeks. In Experiment 2, 300 1-day-old quails were subjected to a different factorial arrangement of treatments with two ME levels (11.51 and 12.13 MJ/kg) and five CP concentrations (210, 220, 230, 240 and 250 g/kg) for 28 days. Experiment 1 revealed that an interaction existed in weight gain between ME and CP levels in weeks 1 to 4. In both ME groups, quails receiving CP of 160 g/kg showed the least weight gains (P<0.05). No differences (P>0.05) existed in weight gain between the ME groups in which quails ingested CP of 250 and 280 g/kg, whereas quails consuming CP of 220 g/kg with an ME of 13.39 MJ/kg had smaller weight gain than did those ingesting higher CP concentrations (P<0.05). Of main effects for weeks 1-4, quails treated with an ME of 12.13 MJ/kg consumed more feed than did those receiving another ME level, whereas quails in both ME treatments showed similar feed efficiencies. For weeks 5 to 8, no difference (P>0.05) in weight gain, feed intake and feed efficiency was seen regardless of ME levels, and no interaction existed between ME and CP levels. In Experiment 2, the best weight gain and feed efficiency were achieved when the dietary CP concentration was more than 210 g/kg, and quails treated with 11.51 MJ/kg showed better weight gain and feed efficiency (P<0.05) than did those that received 12.13 MJ/kg. Furthermore, the weight gains and protein intakes on the basis of per MJ from the two experiments were pooled together to estimate the protein intake necessary for the best growth performance by two mathematic models; they were then converted to dietary CP concentrations of 204 (minimum) and 233 g/kg (maximum) when ME was 11.51 MJ/kg. In conclusion, BBQ will achieve good growth performance with dietary CP of more than 204 g/kg on the basis of an ME of 11.51 MJ/kg in weeks 1 to 4.     

Physiological and biochemical adaptations to training inRana pipiens

Summary FifteenRana pipiens were trained on a treadmill thrice weekly for 6.5 weeks to assess the effects of training on an animal that supports activity primarily through anaerobiosis. Endurance for activity increased 35% in these frogs as a result of training (P=0.006, Fig. 1). This increased performance was not due to enhanced anaerobiosis. Total lactate produced during exercise did not differ significantly for the trained or untrained animals in either gastrocnemius muscle (2.77±0.21 and 2.82±0.13 mg/g, respectively) or whole body (1.32±0.10 and 1.47±0.06 mg/g, respectively). Glycogen depletion also did not differ between the two groups (Fig. 2c). The primary response to training appeared to involve augmentation of aerobic metabolism, a response similar to that reported for mammals. Gastrocnemius muscles of trained frogs underwent a 38% increase over those of untrained individuals in the maximum activity of citrate synthase (14.5±1.0 and 10.5±0.9 moles/(g wet wt·min);P=0.008). This enzyme was also positively correlated with the level of maximum performance for all animals tested (r=0.61,P<0.01) and with the degree of improvement in the trained animals (r=0.72,P<0.05). In addition to an increased aerobic capacity, the trained animals demonstrated a greater removal of lactate from the muscle 15 min after fatigue (Fig. 2b).     

Inducible nitric oxide synthase inhibitor aminoguanidine, differently affects Morris water maze tasks of ovariectomized and naïve female rats

The role of ovarian hormones, nitric oxide, and their interaction on learning and memory has been widely investigated. The objective of present study was to investigate different effects of chronic administration of inducible nitric oxide synthase inhibitor, aminoguanidine (AM) on learning and memory of ovariectomized (OVX) and na?ve (Sham) female rats. Thirty-two rats were divided into four groups: 1) Sham, 2) OVX, 3) Sham-AM and 4) OVX-AM. The animals of Sham-AM and OVX-AM chronically received 100 mg/kg/day of aminoguanidine during 8 weeks before 5 test days. The animals in Sham and OVX groups received 1 ml/kg saline instead of aminoguanidine. The animals were tested in Morris water maze and the escape latency and traveled path to reach the platform were compared between groups. On the fifth day, the platform was removed, and the animals were allowed to swim for 60 s ( prob trial). The time spent in the target quadrant (Q1) was compared between groups.Results showed that the escape latency and traveled path in OVX group were significantly higher than in the Sham group (p<0.01). Both escape latency and traveled path in the Sham-AM group was significantly higher than in the Sham group (p<0.01) however, there was no significant difference between OVX-AM and OVX groups.The time spent by the animals of OVX group in the target quadrant (Q1) during the probe trial was significantly lower than that in the Sham group (p<0.01). The animals of the Sham-AM group spent shorter times in the target quadrant in comparison with the Sham group (p<0.01). There was no significant difference between the OVX and OVX-AM groups in the time spent in tarthe get quadrant. It is concluded that the effect of aminoguanidine on learning and memory is different in the presence or absence of ovarian hormones but it needs further investigation.     

The Maintenance of Traditions in Marmosets: Individual Habit,Not Social Conformity? A Field Experiment

Background

Social conformity is a cornerstone of human culture because it accelerates and maintains the spread of behaviour within a group. Few empirical studies have investigated the role of social conformity in the maintenance of traditions despite an increasing body of literature on the formation of behavioural patterns in non-human animals. The current report presents a field experiment with free-ranging marmosets (Callithrix jacchus) which investigated whether social conformity is necessary for the maintenance of behavioural patterns within groups or whether individual effects such as habit formation would suffice.

Methods

Using a two-action apparatus, we established alternative behavioural patterns in six family groups composed of 36 individuals. These groups experienced only one technique during a training phase and were thereafter tested with two techniques available. The monkeys reliably maintained the trained method over a period of three weeks, despite discovering the alternative technique. Three additional groups were given the same number of sessions, but those 21 individuals could freely choose the method to obtain a reward. In these control groups, an overall bias towards one of the two methods was observed, but animals with a different preference did not adjust towards the group norm. Thirteen of the fifteen animals that discovered both techniques remained with the action with which they were initially successful, independent of the group preference and the type of action (Binomial test: exp. proportion: 0.5, p<0.01).

Conclusions

The results indicate that the maintenance of behavioural patterns within groups 1) could be explained by the first rewarded manipulation and subsequent habit formation and 2) do not require social conformity as a mechanism. After an initial spread of a behaviour throughout a group, this mechanism may lead to a superficial appearance of conformity without the involvement of such a socially and cognitively complex mechanism. This is the first time that such an experiment has been conducted with free-ranging primates.     

A comparison of two exercise training programs on cardiac responsiveness to beta-stimulation in obesity

We demonstrated previously that exercise training did not restore normal cardiac beta-adrenergic responsiveness in obese rabbits. This study tested the hypothesis that an increased training volume was required to attenuate obesity-related reductions in isolated heart responsiveness to isoproterenol. Female New Zealand White rabbits were divided into lean control, lean exercise-trained, obese control, and obese exercise-trained groups. For the exercise-trained groups, total treadmill work over 12 weeks was increased 27% when compared with lean and obese animals trained with lower total training volume. After 12 weeks, Langendorff isolated hearts were used to study developed pressure, +dP/dt(max), and -dP/dt(max) responses to isoproterenol (10(-9) - 3 x 10(-7) M). Concentration-response data were fit to a sigmoidal function using a four-parameter logistic equation. Controls were compared with animals trained under the low- and high-training volume programs using one-way analysis of variance and Tukey's post-hoc test; separate analyses were conducted for lean and obese rabbits. In both lean and obese groups trained under the high-training volume program, EC50 values for +dP/day(tmax) and -dP/dt(max) were higher compared with same-weight controls and animals trained under the low-training volume program, indicating that contractility and relaxation responsiveness to isoproterenol was reduced by the higher training volume. Therefore, these data indicate that increased training volume failed to attenuate obesity-related decrements in isolated heart responsiveness to beta-adrenergic stimulation and caused reduced sensitivity to isoproterenol in both lean and obese animals.     

Effect of training on fibre composition and phosphate metabolites in rest measured in vitro in muscles of young pigs.

1. Fibre type composition and phosphate metabolites were studied in m. longissimus thoracis (MLT), m. rectus femoris (MRF) and m. triceps brachii (MTB) in trained (N = 6) and sedentary (N = 6) pigs. 2. Samples were analyzed histochemically and by means of in vitro 31P NMR spectroscopy. 3. Training (duration 11 weeks) consisted of treadmill running at a speed of 1.1 m/sec. The daily exercise time of trained animals gradually increased from 10 min during the very first days to 60 min at the end of the 4th week. 4. During the final 7 weeks exercise time remained unchanged. Sedentary animals were not subjected to training. 5. A higher proportion of type beta R fibres in MRF, MTB and MLT and a lower proportion of type alpha W fibres were found in the trained group of animals compared to the control group. 6. In MLT no significant differences in the proportion of type alpha W were observed between both groups. 7. No significant differences in average fibre diameter of muscle fibres were found between groups. 8. No differences in concentration of phosphate compounds were observed between trained and sedentary groups. 9. Muscles with a higher proportion of type IIb fibres in both groups of pigs contained higher amounts of phosphocreatine (PCr) and were also characterized by a higher ratio of PCr to inorganic phosphate (Pi).     

Effects of live animals vs. preserved specimens on student learning

Fourth-grade students (292 in all) were tested to determine if handling live animals influences cognitive and affective learning to a greater extent than handling preserved specimens. Live and dried exoskeletons of horseshoe crabs (Limulus polyphemus) and sea stars (Asterias forbesi) were used as contact animals. All students were 1) pre- and posttested; 2) participants in a teacher-directed, “touch-and-feel” lecture; and 3) given a “retention” test 6 weeks following contact. Results indicated that short- and long-term cognitive learning took place when students handled either live or dried animals. However, gains in short- and long-term affective learning (measured by changes in attitude) were achieved only when students handled live animals.     

Use of red pepper oil in quail diets and its effect on performance,carcass measurements,intestinal microbiota,antioxidant indices,immunity and blood constituents

Plant-derived additives are used to maintain the health and growth performance of livestock. The use of red pepper oil (RPO) has recently attracted considerable scientific interest mainly due to its potential benefits for animals and humans. The present study was conducted to evaluate the effect of dietary supplementation with RPO on growth performance, carcass measurements, antioxidant status and immunity of growing quails between 1 and 5 weeks of age. A total of 240 growing quails (1-week old) were distributed into 5 equal groups consisting of 48 birds (4 replicates of 12 birds each). The first group was fed a basal diet without RPO (0 g/kg diet), and the second, third, fourth and fifth groups received diets containing RPO (0.4, 0.8, 1.2, 1.6 g/kg diet, respectively). The experiment lasted for 5 weeks. At age of 5 weeks, quails were slaughtered for carcass examinations, microbiological analysis of intestine and to determine blood constituents. Data were statistically analyzed by one-way ANOVA. Quails fed with 0.8 g RPO/kg diet showed 12.14%, 14.4% and 15% improvement in live BW, body weight gain and feed conversion ratio, respectively, compared with the control group. Quails that received diets with 1.2 g RPO consumed more feed than the others during the total period (1 to 5 weeks). Plasma globulin levels were significantly decreased (P = 0.0102), but albumin/globulin ratio was significantly increased (P = 0.0009) in birds fed diets containing RPO (0.4 and 1.2 g/kg) compared with those in the control group. Activity of liver enzymes in the plasma was nonsignificantly decreased in quails supplemented with 0.8 g RPO/kg diet compared with those in the control group. Activities of antioxidant enzymes (glutathione and catalase) in the group fed on diets supplemented with RPO (0.8 g/kg) were significantly higher than those in the control group. The inclusion of RPO (0.8 g/kg diet) in quail diets improved (P < 0.05) plasma lipid profile and also decreased pH of the caecal content (P = 0.0280) compared with those in the control group. The caecal bacterial population, Salmonella spp., coliform and Escherichia coli, were lowered (P < 0.05) in the groups treated with RPO (0.8, 1.2 and 1.6 g/kg) compared with those in the control group. In conclusion, dietary supplementation of RPO (0.8 g/kg) can enhance the performance and antioxidant indices and decrease intestinal pathogens and thus improve the health status of Japanese quail.     

Effect of chronic supplementation with branched-chain amino acids on the performance and hepatic and muscle glycogen content in trained rats

The objective of this study was to evaluate the effects of a diet supplemented with branched-chain amino acids (BCAA; 3.57% and 4.76%) on the performance and glycogen metabolism of trained rats. Thirty-six adult male Wistar rats received the control diet (AIN-93M) (n=12) and two diets supplemented with BCAA (S1: AIN-93M+3.57% BCAA, n=12, and S2: AIN-93M+4.76% BCAA, n=12) for 6 weeks. The training protocol consisted of bouts of swimming exercise (60 min day(-1)) for 6 weeks at intensities close to the lactate threshold. On the last day of the experiment, all groups were trained for 1 h (1H) or were submitted to the exhaustion test (EX). The time to exhaustion did not differ between groups. The groups submitted to the exhaustion test presented a reduction in plasma glucose and an increase in plasma ammonia and blood lactate concentrations compared to the 1H condition. In the 1H condition, hepatic glycogen concentration was significantly higher in group S2 compared to the control diet and S1 groups (132% and 44%, respectively). Group S2 in the 1H condition presented a higher muscle glycogen concentration (45%) compared to the control diet group. In the EX condition, a significantly higher hepatic glycogen concentration was observed for group S2 compared to the control diet and S1 groups (262% and 222%, respectively). Chronic supplementation with BCAA promoted a higher hepatic and muscle glycogen concentration in trained animals, with this effect being dose dependent.     

Influence of training in the dark or light phase on physiologic and metabolic parameters of Wistar rats submitted to aerobic exercise

Light and dark phase training may influences rodents’ physiologic parameters because these animals have nocturnal habits. Thus, we verify the effects of the training in different photoperiods on metabolism and corporal composition of rats. Eighteen rats were divided into three groups – G1: non-trained; G2: trained in the light phase; G3: trained in the dark phase. Rats were allowed to swim for 60 min, five times per week during six weeks. Trained animals presented a smaller weight gain and fat percentage in carcass. Rats of G3 increased gastrocnemius relative weight. The adipocyte diameter of G3 rats was smaller than the other groups. The levels of the total cholesterol, low-density proteins, and triacylglycerols were decreased in animals of G2 while the glycemia was increased. Training in light phase provided more alterations in the blood biochemical profile while the training in the dark increased the gastrocnemius weight and decreased the diameter of the adipocyte.     

Vasopressin accelerates appetitive discrimination learning and impairs its reversal

Rats were trained in a semi-automated Y maze to find food at the end of the lighted arm. Those treated with 10 μ g lysine vasopressin, 90 min before training learned the response to a $\text{9}\text{10}$ correct choice criterion significantly faster than saline treated animals. There was no difference in rate of forgetting between the treatment groups, as evidenced by a retention test, 3 weeks after training. There was no direct effect of vasopressin on retrieval, since animals treated before the retention test performed at the same level as non treated animals. Finally, vasopressin impaired reversal from light to dark. In a second experiment, the acquisition facilitation seen in Exp. I was replicated, but there was no effect of the treatment on animals trained to dark S_D. However, the impairment seen in Exp. I when vasopressin treated animals, trained to light, were reversed to dark, was replicated in this experiment in animals trained to dark and reversed to light.Previous demonstrations of vasopressin facilitation of learning and memory have, with few exceptions, relied on shock avoidance tasks. The present experiments demonstrate a reliable facilitation of appetitive learning by vasopressin. The fact that vasopressin impairs reversal may be due to an increased tendency to perseverate.     

Combining scientific experimentation with conventional housing: A pilot study with rhesus monkeys

In search of a method to increase the validity of experimental data and simultaneously counteract the negative consequences of restricted laboratory environments, a pilot study was run with three rhesus monkeys (Macaca mulatta), which were trained and tested with a laboratory-type task in the animal housing facility. The testing apparatus was made available to individual animals 24 hours a day at their living cage and was connected to a computer that controlled the test and the distribution of regular monkey chow as reward. The animals were thus able to work whenever they wanted, for whatever period of time they chose, in their accustomed home environment. Besides furnishing data on the distribution of activity and performance over extended periods of time, the study provided more data than those obtained previously when animals were tested each day for only a limited time in an isolated test chamber. It was also found that the self-initiated manipulatory activity required by the test considerably reduced the number of motor stereotypies. Thus, testing animals within the housing facility was profitable for the investigators and beneficial for the animals.     

Conditioned exercise method for use with nonhuman primates

The objective of this study was to demonstrate the feasibility of using appetitive methods to train adult male olive baboons (Papio cynocephalus anubis), who were socially housed and fitted with indwelling catheter/ transducer systems, to exercise on an inclined, motorized, moving treadmill. All subjects were first trained to walk on a motorized treadmill for 30 min at a speed of approximately 1.6 km/hr on a 0 grade. Upon completion of initial exercise training, six animals were assigned to a low exercise group (LOW), six were assigned to a moderate exercise group (MOD), and six were assigned to a sedentary control group (SED). The LOW group exercised 30 min per day on an elevated treadmill, the MOD group exercised 60 min per day on an elevated treadmill and the SED group did not perform any treadmill exercise. The 12 animals comprising the LOW and MOD groups were exercised 4 days per week and their performance was increased over a subsequent 30-week experimental period. We gradually increased speed and grade demands over several weeks and produced an animal model capable of traveling at speeds up to 5.5 km/hr on a 22% grade and distances up to 3,353 m horizontally and 549 m vertically in a 1-hr session. © 1992 Wiley-Liss, Inc.