Anabolic-androgenic steroid increases running endurance in rats

The study was designed to determine whether treatment with an anabolic-androgenic steroid enhances running performance in rats by increasing their freely chosen training distance. Forty male Long-Evans rats were randomly divided into either a sedentary control group or an exercising group caged in specially designed running wheels in which the rats were able to run spontaneously. After 4 wk, both groups were further subdivided into two groups receiving either 0.5-mg Durabolin (nandrolone phenylpropionate) (im) or 0.5-mg saline, every second day. After 8 wk, running distance was similar in both exercising groups. Rats receiving the anabolic-androgenic steroid ran 41% longer during the test of submaximal running endurance compared to the trained rats receiving saline (P < 0.05). Submaximal running endurance was not increased in sedentary rats receiving the anabolic-androgenic steroid. After 4 wk of training, the maximal sprinting speed increased by 29% in trained rats. There was no further increase in maximal sprinting speed after an additional 4 wk of training and treatment with either anabolic-androgenic steroid or saline treatment. Therefore, rats that train spontaneously while being treated with an anabolic-androgenic steroid had increased submaximal running endurance compared with trained rats treated with saline, despite the similar voluntary training distance and skeletal muscle oxidative capacity between the two groups. The mechanism by which treatment with an anabolic-androgenic steroid, combined with training, enhances submaximal running performance could not be identified and needs to be addressed in future studies.     

Differential effects of prenatal stress in two inbred strains of rats

Glucagon-like peptide-1 (GLP-1) may be one of the enterogastrone hormones of the ileal brake mechanism. We therefore studied its effects on gastric lipase secretion in healthy volunteers and vagotomized patients during infusion of pentagastrin. The intestinal incretin hormone GLP-1 (glucagon-like peptide-1, 7-36 amide) was investigated because of its inhibitory effects on gastric acid secretion and motility. GLP-1 infused intravenously in amounts corresponding to the postprandial release significantly inhibited pentagastrin-stimulated gastric lipase secretion and lipolytic activity. The inhibitory effect of GLP-1 persisted in vagotomized patients, suggesting that fundic chief cells, from which gastric lipase is released, or neighboring inhibitory cells could be equipped with GLP-1 receptors. Vagotomized patients had significantly higher plasma concentrations of gastrin and secretin. No significant changes of gastrin, secretin, and CCK secretion were seen during GLP-1 infusion in the vagotomized patients, whereas secretin decreased significantly in the healthy volunteers. GLP-1 seems to be a naturally occurring inhibitor of gastric lipase secretion acting via a nonvagal mechanism. Our results indicate that gastric lipase secretion is subject to hormonal stimulatory as well as inhibitory mechanisms.     

Nucleic acid concentration in the brains of inbred rats of different strains

The changes of nucleic acids content in the formation of conditioned skin-defence reflex was studied on inbred rats of various strains. In WGA rats the reflex was formed on the average aight stimulations. An increased RNA content was discovered by cytophotometric determination of the nucleic acids content in the neurons and perineural glia of the cerebral cortex in August rats only. It is assumed that an increased RNA synthesis in the animals of this strain can serve as the basis for their better training.     

Pre-exercise branched-chain amino acid administration increases endurance performance in rats

This study investigated the effects of pre-exercise branched-chain amino acid (BCAA) administration on blood ammonia levels and on time to exhaustion during treadmill exercise in rats. Adult female Wistar rats were trained on a motor driven treadmill. After a 24-h fast, rats were injected intraperitoneally (i.p.) with 1 mL of placebo or BCAA (30 mg), 5 min before performing 30 min of submaximal exercise (N = 18) or running to exhaustion (N = 12). In both cases, rats were sacrificed immediately following exercise, and blood was collected for the measurement of glucose, nonesterified fatty acid (NEFA), lactic acid, BCAA, ammonia, and free-tryptophan (free-TRP) levels. Control values were obtained from sedentary rats that were subjected to identical treatments and procedures (N = 30). Plasma BCAA levels increased threefold within 5 min after BCAA administration. Mean run time to exhaustion was significantly longer (P < 0.01) after BCAA administration (99 +/- 9 min) compared with placebo (76 +/- 4 min). During exercise, blood ammonia levels were significantly higher (P < 0.01) in the BCAA treated compared with those in the placebo treated rats both in the 30-min exercise bout (113 +/- 25 mumol.L-1 (BCAA) vs 89 +/- 16 mumol.L-1) and following exercise to exhaustion (186 +/- 44 mumol.L-1 (BCAA) vs 123 +/- 19 mumol.L-1). These data demonstrate that BCAA administration in rats results in enhanced endurance performance and an increase in blood ammonia during exercise.     

Influence of carbohydrate supplementation early in exercise on endurance running capacity

The aim of this study is to examine the effect of carbohydrate (CHO) ingestion during the first hour of treadmill running on endurance capacity. Eleven male subjects ran at 70% VO2max to exhaustion on three occasions one week apart. On two occasions two CHO-electrolyte solutions (a 5.5% (E) and a 6.9% (L) were ingested for the first hour of exercise; water was ingested until exhaustion. On the third occasion water (W) was ingested throughout the run. The order testing was randomly assigned. Exhaustion times for the W, E, and L trials were 109.6 +/- 9.6 min, 124.5 +/- 8.4 min, and 121.4 +/- 9.4 min, respectively. There was no difference between the two CHO trials, but time to exhaustion was longer only for the E trial (P < 0.05), compared with the W trial. Nevertheless the average performance times for the combined results of the two CHO trials were longer than the water trial. Carbohydrate ingestion resulted in higher blood glucose concentration (P < 0.01) at 20 min in the E trail only and lower (P < 0.05) serum growth hormone and plasma FFA and glycerol concentrations at 60 min but not at exhaustion in both E and L trials compared with the W trial. Blood lactate, plasma ammonia, electrolytes, catecholamines, and serum insulin and cortisol concentrations were not different in the three trials. In conclusion, CHO ingestion during the first hour of exercise improves endurance capacity go a greater extent compared with water alone.     

Open-field behavior in four inbred mouse strains.

Describes an objective, detailed analysis of the open-field behavior of 4 inbred strains of mice: A, BALB/C, C57BL/6, and DBA/2. During a 20-min period, 400 observations were made of the behavior of an S and scored into categories such as rearing, locomotion, grooming, sniffing at objects, freezing, etc. Significant differences between Ss of different strains were observed with regard to frequency of categories. The changes in frequency over time were strain-dependent for some behaviors. Some acts (e.g., rearing and grooming) occurred more frequently with the passage of time, whereas others changed little or decreased in frequency (e.g., sniffing at objects). The very infrequent occurrence of freezing behavior could not account for the large differences in activity between strains. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear-potentiated startle in two strains of inbred mice.

The fear-potentiated startle paradigm has been used with great success to examine conditioned fear in both rats and humans. The purpose of this study was to examine fear-potentiated startle in inbred mice. One-month-old C57BL/6J (C57) and DBA/2J (DBA) mice were given tone?+?foot shock training trials. The amplitude of the acoustic startle reflex was measured in the presence and absence of the tone both before and after training. Both strains showed fear-potentiated startle after training as evidenced by larger startle amplitudes in the presence of the tone than in its absence. However, the magnitude of fear-potentiated startle was greater in DBA mice than in C57 mice. These results not only demonstrate fear-potentiated startle in mice for the first time but also suggest that fear-potentiated startle can be influenced by characteristics of the mouse strain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genotype dependence of monoamine oxidase in inbred strains of mice

MAO activity was found to be influenced by the genotype or strain of mouse up to 20 days of age. The strain differences observed may derive from different rates of brain development. A number of neurological mutations comprizing three pathological classes had no effect on MAO.     

A study of oral morphine preference in inbred mouse strains

The generative potential of free perichondrial grafts from rabbit auricular and rib cartilage around a self-reinforced polyglycolic acid (SR-PGA) rod was examined in eight growing rabbits. A 15 x 15 mm perichondrial graft was dissected away from the posterior side of each auricular cartilage. One graft was wrapped around a 1.1 x 10 mm SR-PGA rod and the other served as a control and was shaped into a tube without an implant. Fifth rib cartilages were then resected subperichondrially on both sides. The remaining perichondrium on the other side was wrapped around a 1.1 x 10 mm SR-PGA rod, while the other served as a control and was shaped into a tube without an implant. All the grafts were placed inside pectoralis major muscles. Grafts were biopsied six weeks postoperatively. Neocartilage formation was seen in all grafts with one exception on both the implant and control sides. It formed a tube-like structure around the implant in four cases after grafting of auricular perichondrium and in three cases after grafting of rib perichondrium. New bone formation was also observed. SR-PGA implants did not seem to disturb the generative potential of perichondrium.     

Primary aggressive motivation in three inbred strains of mice.

30 male mice from 3 inbred strains (BALB/cJ, RF/J, and SJL/J), isolated since 35 days of age, were run at 135 days in a T maze, and acquired a position response when the opportunity to attack a nonaggressive S was used as a reinforcer. Results are interpreted as evidence for primary intraspecific aggressive motivation. Strain differences were significant. Significant warm-up effects were also obtained, including persistent increases in number of correct T-maze choices from 1st to later trials given each day. An identically composed group of 30 food-deprived Ss were run in the maze for food reward. Eating was uniformly a highly effective reinforcer. However, in the 2 best-performing strains the effectiveness of aggression reinforcement following warm-up approached that of reinforcement by eating. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The laboratory assessment of endurance performance in cyclists

Performance in endurance activities depends on maximal aerobic capacity (VO2max) and the ability to sustain a high percentage of VO2max over time. This study examined whether noninvasive laboratory measures would be valid predictors of endurance performance in an individual-start bicycle race (TT). Eight experienced male cyclists (age = 25.1 +/- 3.3 years, weight = 75.0 +/- 5.7 kg, VO2max = 5.05 +/- 0.4 L.min-1) performed a progressive incremental exercise test to exhaustion on a cycle ergometer. VO2max, maximum power output, and ventilatory threshold were determined. Later the subjects completed a 40-km TT. Power output at the ventilatory threshold (VT watts) was correlated with race performance time and calculated power output during the competition (r = -0.81; r = 0.82). VT watts and VO2max accounted for 75% of the variance between subjects (r = 0.91) in performance time. These data indicate that simple laboratory measures can predict TT performance in trained cyclists. Individual differences may be accounted for by motivation, aerodynamic position, and efficiency.     

Genealogy of the 129 inbred strains: 129/SvJ is a contaminated inbred strain

The 129 mouse is the most widely used strain in gene targeting experiments. However, numerous substrains exist with demonstrable physiological differences. In this study a set of simple sequence length polymorphisms (SSLPs) was used to determine the relatedness of selected 129 substrains. 129/SvJ was significantly different from the other 129 substrains and is more accurately classified as a recombinant congenic strain (129cX/Sv), being derived from 129/Sv and an unknown strain. This mixed genetic background could complicate gene targeting experiments by reducing homologous recombination efficiency when constructs and ES cells are not derived from the same 129 substrain. Additionally, discrepancies due to different genetic backgrounds may arise when comparing phenotypes of genes targeted in different 129-derived ES cell lines.     

Characterization of phenytoin-resistant kindled rats, a new model of drug-resistant partial epilepsy: comparison of inbred strains

PURPOSE: Previous work from our laboratory showed that amygdala-kindled Wistar outbred rats can be selected according to the increase of afterdischarge threshold (ADT) after phenytoin application. Animals that consistently do not respond to phenytoin (PHT) with an ADT increase (non-responders) are the first animal model of pharmacoresistant complex partial seizures. In this study, we determined the ability to respond to PHT in male kindled rats of different inbred strains. METHODS: The experiments were performed in fully kindled rats of five different inbred strains, Wistar-Kyoto, Lewis, Fischer 344, ACI, and Brown Norway. The response type of each rat was revealed by four consecutive PHT applications (75 mg/kg, i.p.) in fully kindled rats. RESULTS: PHT application resulted in plasma concentrations ranging from some 16 microg/ml in Lewis rats to 35 microg/ml in Fischer 344 rats, and in slight ataxia, most strongly in Fischer 344 rats. The rats of each strain did not show a homogeneous response to PHT. A significant increase of ADT was found after 86-97% of applications in Lewis, Wistar-Kyoto, and Fischer 344 rats. In contrast, Brown Norway rats responded in only 34% of experiments. This led to a considerable number of responders (i.e., consistent ADT increase by >20%) in Fischer 344, Wistar-Kyoto, and Lewis rats. The only strain revealing nonresponders (i.e., consistent lack of ADT increase by >20% with PHT treatment) was Brown Norway. CONCLUSIONS: Inbred strains, although genetically more homogenous than outbred strains, differ in their response to PHT. Brown Norway rats can offer advantages for further detailed investigation of the resistance to PHT in the kindling model of complex partial seizures.     

Ethanol-induced conditioned taste aversion in 15 inbred mouse strains.

This study used a genetic correlational strategy to characterize the neurobiological basis of ethanol's (0, 2, or 4 g/kg) aversive effects as indexed by conditioned taste aversion. Substantial strain differences in taste aversion and hypothermia were observed, but the genetic correlation between these phenotypes was not significant. However, significant genetic correlations were observed between taste aversion and ethanol-related behaviors measured in previous studies, including home-cage ethanol preference (r = .68) and ethanol withdrawal severity (r = -.69). Strains showing stronger taste aversion tended to show lower ethanol preference and higher withdrawal severity. This pattern of findings is consistent with previous studies suggesting a commonality in neurobiological mechanisms underlying these phenotypes. These results do not support the hypothesis that ethanol-induced taste aversion is mediated by the drug's rewarding properties. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in kindling development in seven outbred and inbred rat strains

The kindling phenomenon, i.e., the progressive development of focal and secondarily generalized seizures upon repeated electrical stimulation of a limbic brain region, occurs in various species, but with marked differences in kindling rate between species and also within the same species. In rats, differences in kindling rates have been reported within the same strain and between different strains, and both genetic and environmental influences are thought to be involved in this variability. In most studies on kindling in rats, outbred strains such as Sprague-Dawley have been used. In the present study, we compared rates of amygdala kindling development in two outbred (Sprague-Dawley, Wistar) and five inbred (Lewis, Fischer 344, ACI, Wistar-Kyoto, Brown Norway) rat strains, including several strains which have not been kindled before. We were particularly interested which parts of the stepwise progression of kindling differ among these strains. Furthermore, the sensitivity of the basolateral amygdala to electrical stimulation was determined before and after kindling. Once daily electrical stimulation of the basolateral amygdala resulted in marked interstrain differences in kindling rates, with Sprague-Dawley and Brown-Norway rats exhibiting the lowest number of stimulations to reach fully kindled (stage 5) seizures, and Lewis rats showing the highest number of the 7 strains. In contrast to the significant differences in number of stimulations to reach the fully kindled state, total (cumulative) afterdischarge duration (ADD) to reach stage 5 did not significantly differ among strains, substantiating that cumulative AD is the principal factor in the acquisition of kindled seizures. Marked differences in ADD of a stage 5 seizure were obtained between strains, with strains kindling rapidly exhibiting longer ADD than strains kindling slowly. Postkindling afterdischarge threshold (ADT) varied significantly among strains, but only 3 of the 7 strains showed a decrease of ADT compared to prekindling values. When the stepwise progression of kindling was evaluated, pronounced interstrain differences were determined in the time spent in the initial phase of kindling, i.e., stage 1 seizures, both in terms of stimulations and cumulative ADD, indicating that variations in kindling rates were predominantly due to the time needed to progress from stage 1 to subsequent stages of the kindling process. The data seem to indicate that inbred rat strains offer an interesting resource for dissecting the underlying genetic basis for phenotypic differences in epileptogenesis as induced by kindling, although the high variability of kindling rates seen within some inbred strains weakens this possibility.     

Dietary fatty acid profile affects endurance in rats

Typically athletes are advised to increase their consumption of carbohydrates for energy and, along with the general population, to reduce consumption of saturated fats. It is now recognized that fats are not identical in their influence on metabolism, and we argue that the composition of the polyunsaturated fat component should not be ignored. The aim of this study was to manipulate the dietary fatty acid profile in a high-carbohydrate diet in order to investigate the effect of dietary polyunsaturates on submaximal endurance performance in rats. Rats were fed one of three isoenergetic diets containing 22 energy percentage (E%) fat for 9 wk. The diets comprised an essential fatty acid-deficient diet (containing mainly saturated fatty acids); a diet high in n-6 fatty acids, High n-6; and a diet enriched with n-3 fatty acids, High n-3. Submaximal endurance in rats fed the High n-3 diet was 44% less than in rats fed the High n-6 diet (P < 0.02). All rats were then fed a standard commercial laboratory diet for a 6-wk recovery period, and their performances were reevaluated. Although endurance in all groups was lower then at 9 wk, it was again significantly 50% lower in the High n-3 group than the High n-6 group (P < 0.005). Although n-3 fats are considered beneficial for cardiovascular health, they appear to reduce endurance times, and their side effects need to be further investigated.