Biomedical subjects

J Alliot

Publications and source records attributed to J Alliot.

13 recordsLinked to original sources

PubMed2000

Age-related changes in adaptive macronutrient intake in swimming male and female Lou rats.

To evaluate the age-related changes in capacity to adjust the nutrient intake to needs, self-selecting male and female Lou/C/jall rats of 4, 6, 12, 16 and 23 months of age were submitted to a swimming exercise. They were given 6 consecutive days of moderate intensity training (3 x 15 minutes per day). Exercise and postexercise periods were compared with results from the pretraining period. During swimming, a body weight loss and a decrease in both caloric intake and fat selection were observed. This effect was more marked in older groups compared to 4 month-old groups. An increase in protein intake was observed in females, specially in older groups, whereas no effect was seen in males. The ability to increase caloric ingestion and regain weight during the postexercise period decreased with advancing age and was better in females than in males. We also showed an age-related effect on the recovery of initial nutrient intake rate that was more pronounced and more precocious for males. Moreover, males tended to decrease their protein intake, whereas females significantly increased it. The present findings suggest a decrease of capacity of adjusting feeding behavior to metabolic needs in aged rats, may be due to a deterioration of the central control of food intake.

Adaptation, Physiological↗

PubMed2000

Age-related changes in nociception and effect of morphine in the Lou rat.

Little is known about how the ageing process affects pain sensitivity and a relevant animal model is therefore required. The effect of age on pain reactivity in animals has been investigated by several experimenters but the results are conflicting. Four groups of male and female Lou/C/Jall rats (4-29 months old) were used for our study. Four pain tests based on evaluation of reflex or more integrated behaviours after a thermal (tail immersion test) or mechanical (paw pressure test and von Frey test) stimulation were used. With mechanical stimulus, a significant decrease in the pain threshold across age was observed, females were more sensitive than males. This increase in nociceptive sensitivity to mechanical stimulation was more pronounced on integrated behaviours (struggle reaction) than on withdrawal reflex. An age-related increase in sensitivity was found on von Frey test. No effect on the latency of reflex induced by thermal stimulation was observed. In addition, a decrease in the spontaneous motor activity during exploration was observed across ageing; this effect was more marked for the females. The effect of morphine at doses of 1, 3 and 9 mg/kg (s.c.) decreased in intensity across ageing. These data demonstrate the need to use (1) various noxious stimuli because differences were observed in the modification of pain reactivity according to the nature of the stimulus; (2) various pain parameters and particularly integrated behaviours; (3) several age groups. In addition, Lou/C/Jall rat could be a useful model for studying of effect of age on pain.

Aging↗

PubMed1999

Peripheral injection of growth hormone stimulates protein intake in aged male and female Lou rats.

It is well established that growth hormone (GH) induces growth rate and food efficiency and stimulates protein accretion in young mammals. Senescence is characterized by metabolic and hormonal disorders, particularly a decrease in protein turnover, which could be correlated to a decrease in GH and insulin-like growth factor I (IGF-I) secretion. We have shown that body weight, protein intake, and IGF-I plasma levels are greatly decreased with aging in Lou/C rats, particularly in males. In order to specify the GH effect on protein intake during aging, males and females (6, 19, and 24 mo) placed on a self-selection regimen were injected daily with a physiological dose of human GH (0.023 mg/rat sc). No GH effect on caloric intake was observed. Nevertheless, GH treatment stimulated body weight in older rats. It also increased protein intake in females and older males (19-24 mo). This stimulating effect was positively correlated with the degree of weight loss in senescent rats, suggesting that the decrease in protein intake observed with aging could be a marker of senescence.

Aging↗

PubMed1998

Age-related changes in adaptive mechanisms of macronutrient self-selection: evidence for a sexual dimorphism.

The effect of aging on patterns of food intake and nutrient selection was investigated using a longitudinal study. Male (n = 10) and female (n = 10) Wistar-Lou rats from 4 to 28 months of age were repeatedly submitted to a macronutrient self-selection (S-S) regimen while controls were maintained under a standard chow diet (Std). An age-related shift of preferences from CHO to fat diets, and a decrease in protein intake for both males and females were evident. Nevertheless, all these modifications were more pronounced and precocious for males. Physical exercise (45 min/day of swimming, on 6 days) induced a body weight loss and an hypophagia more pronounced for males than for females. S-S regimen results revealed that hypophagia concerned exclusively fat intake and that females significantly increased protein intake during and after the exercise period. Study of longevity curves showed a decrease of the mortality in S-S submitted male rats compared to control rats. This study shows that aging induces a sex-difference in feeding patterns which undoubtedly reveals a sex-difference metabolic requirements. Moreover, these results suggest that allowing rats to select macronutrient intakes could delay the process of senescence.

Adaptation, Physiological↗

PubMed1998

Dietary self-selection can compensate an age-related decrease of rat liver 20 S proteasome activity observed with standard diet.

Aged Lou female rats (33 months) submitted to a self-selection regimen showed a decrease in protein intake (down to 11% of the total intake), whereas mature rats (18 months) selected a high percentage of protein (20% of the total intake) similar to the protein content of the standard diet. To find out if this decrease in protein intake would prevent an observed age-related decrease in proteasome activity, four peptidase activities and oxidized protein degradation were tested with proteasome purified from the liver of 18- and 33-month-old rats. The peptidylglutamyl-peptide hydrolase activity, which is decreased with age for rats fed the standard diet, was restored in the self-selecting old rats to the level observed for the mature rats. Degradation of oxidized glutamine synthetase, which is also decreased with age for rats fed the standard diet, was partly restored. Proteasome from self-selecting old rats showed a slight increase in trypsin-like and chymotrypsin-like activities as compared to proteasome from old rats fed the standard diet. Two-dimensional gel electrophoresis followed by quantitative analysis of the pattern of proteasome subunits revealed an increase in the intensity of two protein spots for proteasome from old rats fed the standard diet as compared with proteasome from either mature rats or self-selecting old rats. These findings may have important implications in aging for proteasome-mediated proteolysis and subsequent accumulation of oxidatively damaged protein.

Aging↗

PubMed1997

Changes in pattern of macronutrient intake during aging in male and female rats.

Transversal and longitudinal studies of the natural patterns of food intake were made in male (n = 65) and female (n = 52) Lou rats, from 4 to 34 months of age. The efficiency of body weight control, especially for females, seems to be a main feature of this strain of rat: these rats are small eaters, have lighter body weight, show no development of obesity with age, and have a longer life expectancy than other common strains of rat. A better adaptation to feeding schedules was shown by female groups throughout the experiments. Moreover, an increased consumption for the oldest animals (from 28 months) enables them to keep their body weight constant up to age 34 months, whereas the male rats gradually lost weight with old age (from 28 months). When male and female rats of different age groups were allowed to choose their diet from pure macronutrient sources (protein, fat, and carbohydrate), an age-related shift of preferences from carbohydrate to fat diets was evidenced during daily energy intake. Protein intake also decreased according to age, earlier for males (around 21 months) than for females (34 months).

Aging↗

PubMed1993

Administration of LHRH analog can improve working memory in aged female rats.

We had previously found that an age-related deficit in working memory appeared in middle-aged females, possibly related to their ageing reproductive system. This experiment investigates the effect of administering an analog of luteinizing hormone-releasing hormone (LHRH), D-Trp6-LHRH, to 22-mo-old female rats submitted to successive trainings in a water-reinforced matching to sample task since the age of three months. Animals were injected SC with a long-lasting microcapsule formulation (800 micrograms/kg continuously releasing 5 micrograms D-Trp6-LHRH per day for at least 28 days). The action of the analog on ovary weight and estradiol and progesterone levels was also studied. Administration of D-Trp6-LHRH counteracted the deleterious effect of age on performance and inhibited ovary function. However, hormone plasma levels were not modified. These results suggest that the hypothalamo-ovarian axis might be implicated in memory deficits of middle-aged females.

Aging↗

PubMed1992

Effect of administration of an analog of LHRH on appetitive learning in young and middle-aged female rats.

Hypothalamic luteinizing hormone-releasing hormone (LH-RH) had been reported to induce changes in defensive learning. In middle age, females exhibit a decline in their reproductive axis. Several studies in rodents suggested that hypothalamic LHRH function deteriorated in middle-aged females. Our experiments compare T-maze learning in young and middle-aged female rats and study the effect of administration of an analog of LHRH, D-Trp6-LHRH. The ovarian action of the analog was studied and a gonadectomized control group was added. No differences were observed between young and middle-aged females in acquisition, retention, and reversal of a simple discrimination in the T-maze. However, after removal of motor and spatial cues acquisition of the discrimination on visual cues was impaired in middle-aged females compared to young mature ones. Administration of D-Trp6-LHRH enhanced performance during the visual discrimination in younger females and had no action in middle-aged ones, whereas it inhibited ovary function in both groups. Ovariectomy had no effect. These results suggest a direct effect of the analog of LHRH on the CNS and show that this peptide fails to counteract the deleterious effect of age on performance.

Aging↗

PubMed1991

Food-restriction interacts with vasopressin modulation of activity.

The effects of peripheral injection of various doses of lysine-vasopressin (LVP), administered 30 min before a 5-min session in a hole-board apparatus, were compared as a function of food restriction. Comparison of performance for various indices of general activity clearly showed that the food-restricted rats were more active and exhibited less photophobia than normally fed ones. The differences between the two groups were maintained in a second session 24 hours later. There was no sign of behavioral habituation to the apparatus among restricted animals. Different doses (0.2, 1, 2 micrograms of LVP) affected food-restricted animals differently from the rats fed ad lib. Only the highest dose reduced activity in both groups. A posttest injection of the smallest dose (0.2 micrograms) had an opposite effect on the activity in the hole-board, measured 24 hours after the injection. A second experiment showed that plasma and adrenal corticosterone were higher in deprived rats. The administration of 0.2 micrograms of LVP was followed by an increase in corticosterone. In food-restricted rats this increase was bigger and was still observed 24 hours after the injection. There is an interaction between feeding conditions and LVP injections which affects both the internal hormonal state and spontaneous reactivity to environment. These findings are of relevance to the effect of vasopressin on behavior.

Animals↗

PubMed1991

Acquisition of a matching-to-sample task in young and middle-aged male and female rats.

Male and female rats were trained in a water-reinforced matching-to-sample task. The rule was acquired more rapidly by the females. After initial training, the retention of the rule was measured when the rats were twelve and 14 months old. The performance of neither group was modified at twelve months, but at 14 months, while no change appeared in the performance of males, females showed a drop in correct responses. Training in a modified device which made the task more difficult induced no changes in performance. Final training (at 18 months) showed the drop in performance in females had persisted. The decline of performance in middle-aged females might be related to the ageing female reproductive system.

Aging↗

PubMed1990

Effects of vasopressin on spontaneous black-white choices in a T-maze.

The effects of subcutaneous administration of vasopressin on spontaneous black-white choice were investigated to determine whether they could account for modifications of performances during learning. First, pretrial injections of 0.2 microgram of lysine-vasopressin (LVP) were given to rats fed ad lib submitted after the last injection to ten consecutive choices in the T-maze. Rats received one or five injections and were tested after either 30 minutes or 24 hours. Treatment with LVP reduced natural photophobia and modified the activity. A more striking effect was observed after one injection and with an injection-test interval of 30 min. Second, the influence of repeated injections of LVP on free choices was studied in food-motivated rats. The effect of repeated injections was marked, suggesting greater sensitivity to treatment in such rats. Third, we compared the action of posttrial administration of the peptide on the behavior of food-restricted rats submitted to appetitive learning in the T-maze, or to free choices. The treatment slightly disturbed the learning of the white arm and altered the preference for black in free choices condition. The two actions were different, showing that the effect on spontaneous behavior cannot account for the effect on learning.

Animals↗

PubMed1987

Vasopressin injections impair working memory in a delayed matching to sample task in rats.

Effects of vasopressin were measured in a nonspatial working memory task: food-reinforced, delayed matching to sample. Subcutaneous injections of 0.2 microgram of lysine vasopressin (LVP) or saline were alternately administered to Sprague-Dawley rats after the presentation of the sample and compared to the effect of the same treatments given to a yoked control group of rats. Different durations of sample presentation (5 and 30 min) and various retention intervals (10 min, 3 h, 24 h) were selected. The results showed that LVP never facilitated retention performance: there was no improvement under conditions of weak memory (short presentation of the sample and long retention interval); moreover LVP abolished the facilitation normally obtained when either the length of the sample presentation was longer or the duration of the retention interval was shorter. The performance after the injection of the peptide was differentially impaired, according to brightness of the sample which had been presented: after the presentation of the white box, LVP injections lead to more errors and after that of the black one the treatment induced an increase in latencies of response. All these data may suggest that the physiological consequences of hormonal modifications triggered by the LVP injection are processed along with the stimuli of the learning episode and interfere with the learned positive value of the sample.

Animals↗

PubMed1982

Effects of posttrial vasopressin injections on appetitively motivated learning in rats.

Sixty male rats, maintained on 23-hr food deprivation were trained on two types of appetitive tasks: bar pressure responding under a CRF schedule, and under a differentially reinforced (light+, dark-) schedule. Performance of rats treated with lysing vasopressin, injected immediately after each training session, was compared to that of control animals injected with saline. In the CRF stage, treated animals reached learning criterion significantly later than did control rats, and made significantly fewer bar presses. During acquisition and extinction of a light-dark discrimination, learning and retention were not altered by vasopressin, though the number of bar presses was significantly decreased, and a differential effect was found according to previous CRF performance. The results are discussed considering the hypothesis of a facilitatory effect of vasopressin on memory processes.

Animals↗