Biomedical subjects

B Dib

Publications and source records attributed to B Dib.

At least 19 recordsLinked to original sources

PubMed2005

Rats desensitized by capsaicin alter their food intake regulation especially at cold ambient temperature.

Adult rats were treated subcutaneously for 10 days with capsaicin, and their food intake and body weight were recorded for almost 6 weeks after stopping the treatment. The animals were exposed to different ambient temperatures: Ta (22, 32, 35, 10 and 22 degrees C). In the capsaicin-treated group a persistent increase in food intake and a reduction of body weight were observed when the animals were exposed to the lowest Ta of 10 degrees C. Starting from this temperature, food intake remained significantly higher than in controls until the end of the experiment at a Ta of 22 degrees C. The discrepancy between body weight increase and food intake especially at low temperature (10 degrees C) suggests that capsaicin could prevent suppression of food intake through the mediation of capsaicin-sensitive vagal afferent fibers by activation of cold-temperature-sensitive receptors.

Animals↗

PubMed2001

Intracerebroventricular capsaicin and food intake in the rat.

To investigate whether capsaicin affected food intake and body weight and/or interfered with the mechanisms regulating the body temperature, capsaicin was administered intracerebroventricularly to rats at a daily dose of 25 micrograms of 5 microliters of vehicle for 10 consecutive days. The vehicle consisted of 5% ethanol plus 5% Tween 80 in isotonic saline. The ambient temperature (Ta) was 22 degrees C. Two control groups were used: the first group was treated with the vehicle but its concentration was lowered 10 times in order to avoid the wellknown brain toxicity of Tween 80; the second group was injected with NaCl 0.9% alone. The subsequent observation period lasted 38 days and the rats were exposed to a Ta of 22, 32, 35, 10 and 22 degrees C for different times. Food intake and body weight showed a remarkable decrease during the treatment period in both the capsaicin- and vehicle-treated groups. During the observation period, food intake behavior and body weight evolution were different among the three groups of treated rats. The influence of Ta was most apparent in the capsaicin-treated rats that showed a long-lasting deficit in their body weight and a clear inability to regulate their body temperature (Tb) in a warm environment (Ta 35 degrees C). However, the capsaicin-treated rats began to recover from the weight loss when they were finally housed at Ta 22 degrees C. Tween 80-treated rats began to recover from the weight loss earlier, the pretreatment body weight having been reached during Ta 32 degrees C exposure, i.e., 12 days after the end of the treatment. Since capsaicin did not reduce food intake for a long time during the recovery process, the effect of capsaicin on Ta and body weight seems to be related to metabolic processes. Under the conditions of the present study, neither capsaicin nor Tween 80 seem to have permanently impaired the animals' energy balance regulation.

Animals↗

PubMed2001

Hyperalgesic effect of intrathecally administered interleukin-1 in rats.

The present study demonstrates that intrathecal injection of interleukin-1 (IL-1) in rats at a dose of 50 pg or 500 pg induced a significant hyperalgesic effect in the hot-plate test. The hyperalgesia or the altered nociceptive responses were not considered to be the result of sensitization to the hot plate, since the nociceptive alteration caused by intrathecal administration of IL-1 stopped after 20 min. The results suggest that IL-1 can affect pain responsiveness in a dose-dependent manner and that it is able to modulate neuronal functions. Taken together, our findings and the data from the literature suggest that IL-1-induced hyperalgesia is related not only to the route of administration but also to the algesia testing method used.

Animals↗

PubMed1999

Food and water intake suppression by intracerebroventricular administration of substance P in food- and water-deprived rats.

The purpose of this present experiment was to determine the effect of substance P (SP) on the feeding and drinking behavior. This was investigated in male rats totally food and water deprived for a period of 24 h. The intracerebroventricular (i.c.v.) administration of SP (20 microg 10 microl-1 rat-1) suppressed food and water intakes during the 8 h following administration. At 24 h after i.c.v. injection of SP, the rats were not recovered 10.5% of their feeding and 24.9% of their drinking behavior. However, contrary to what happened with SP, i.c.v. injection of the vehicle of SP did not suppress feeding and drinking behavior, as was observed also in the rats (second control) cannulated i.c.v. but which did not receive any injection. At 48 h after SP injection, no alteration of food and water intakes was observed. These results indicated that SP may function as an endogenous anorexigenic peptide.

Animals↗

PubMed1998

Interleukin-1 and nociception in the rat.

It has recently become accepted that several cytokines may affect peripheral and central nervous system functions. Consistently with these findings, accumulating evidence points toward an important role for interleukin- in the modulation of nociceptive information. Here we review the observations collected after the administration of this cytokine by intracerebroventricular, intrathecal or peripheral route in rats. Taken together, these data suggest that IL-1 can differently affect pain responsivity depending on the dose and the site of action, and clearly demonstrate that this immune factor is deeply involved in the modulation of neuronal functions.

Animals↗

PubMed1998

Intracerebroventricular injection of capsaicin or substance P provokes the micturition reflex in the rat.

Acute intracerebroventricular injection of 25 micrograms capsaicin or 40 micrograms substance P in isotonic saline elicited approximately similar effects on the micturition reflex, but capsaicin had twice as much effect as substance P. This effect is specific, since acute intracerebroventricular injection of isotonic saline did not produce the micturition reflex. It can be hypothesized that capsaicin and substance P may act on the brain micturition centers directly or by mediation of neuropeptides such as tachykinins, but other hypotheses are also made.

Animals↗

PubMed1997

Intracerebroventricular self-injection of beta-endorphin by rats in response to intermittent electrical shocks.

Rats were taught to self-administer beta-endorphin (0.1 microgram or 0.5 microgram/microliter) or NaCl 9% by pressing a lever that activated a pump connected with a cannula implanted in the lateral cerebral ventricle (icv). The pump delivered 1 microliter at each lever pressing. After a training period of 2 weeks, the self-injection behaviour was studied before, during and after nociceptive stimulation. In response to a nociceptive stimulation, 4 rats increased their self-injection of beta-endorphin at 0.5 microgram/microliter per injection. This effect is specific for beta-endorphin since under identical conditions 6 rats did not increase the injection of isotonic NaCl saline solution. Another 6 rats did not increase their self-injection during nociceptive electrical stimulation and the post-nociceptive period when the dose of beta-endorphin was 0.1 microgram/microliter per injection. However these animals self-administered significantly higher levels of beta-endorphin during the pre-control period. Also studied were the acute effects of 10 micrograms of icv beta-endorphin on tail-flick latency in sec. The acute administration of 10 micrograms of beta-endorphin induced a long-lasting analgesia. The results show that the rats increased beta-endorphin self-administration during the pre-control period when the dose was 0.1 microgram/microliter and during the nociceptive stimulation period when the dose was 0.5 microgram/microliter. In the former case the self-administration had the profile of a voluntary doping drug intake, in the latter case the profile was that of an antalgic self-medication.

Analgesics, Opioid↗

PubMed1996

Convulsions and death induced in rats by Tween 80 are prevented by capsaicin.

Two or three minutes after intracerebroventricular (i.c.v.) injection of Tween 80 plus ethanol as vehicles for capsaicin, strong convulsive movements occurred in the treated rats; they twisted and turned, dashed themselves against their cage and all died. Tween 80 in saline without ethanol also produced convulsions and death in all the rats treated. Capsaicin dissolved in the vehicle seemed to furnish protection against such death. Moreover, when capsaicin in Tween 80 was administered i.c.v. 10 min before the Tween vehicle it prevented the death which would have been caused by the i.c.v. vehicle. Thus a new effect is added to those already discovered in the numerous pharmacological studies on capsaicin.

Animals↗

PubMed1994

Thermogenesis in brown adipose tissue is activated by electrical stimulation of the rat dorsal raphe nucleus.

Brainstem mechanisms involved in the central control of thermogenesis in brown adipose tissue (BAT) were investigated, in urethane-anaesthetized rats, by observing changes in the temperature of interscapular BAT following electrical stimulation of sites in the dorsal raphe nucleus (DRN). Large increases in temperature could be produced by single 30 s stimulation trains. The magnitude of the temperature increase grew as a function of both current and frequency. Non-linear temporal summation was observed when near-threshold trains were delivered in close succession. These results are consistent with the view that ascending projections from the DRN relay thermal information to the basal forebrain and hypothalamus.

Adipose Tissue, Brown↗

PubMed1994

New technique for cannulae implantation into the dorsal raphe nucleus using layer 5 of cerebellum reference in rat stereotaxic surgery.

A new surgical method for needle or electrode implantation using layer 5 of the cerebellum (C5) as anatomical reference in rat stereotaxic surgery was developed. The coordinates of the new technique for electrode or needle implantation into dorsal raphe nucleus (DRN) are: PA: 3.20-340 mm, V: 6.00-6.40 mm, and L: 0.00 mm. The success of the new surgical procedure was confirmed by histological control of the lesion impact of the electrode into NRD. This lesion impact was well positioned in 83-86% of implanted rats. The use of this method can be extended to other nuclei than the DRN of the brain for cannula implantation. In addition, it can be used in rats on a larger scale, because it suppresses the limitations due to age and body weight.

Adipose Tissue, Brown↗

PubMed1991

Chronic intrathecal cannulation affects hypothalamic opioids depending on the technique employed.

Previous studies have shown that chronic intrathecal cannulation can interfere with the homeostasis of central opioid peptides. These results show that beta-endorphin and Met-enkephalin concentrations did not change in the hypothalamus of rats bearing a chronic cannula inserted between C8-T1 up to L3 and fixed to the processes transversus T1. These results suggest that chronically cannulated rats can be considered as normal when studying hypothalamic beta-endorphin or Met-enkephalin concentrations, and used in physiological studies, depending on the technique employed.

Animals↗

PubMed1990

After two weeks habituation to capsaicinized food, rats prefer this to plain food.

In a first series of experiments rats were accustomed for two weeks to eat chow with capsaicin (250 micrograms: 1 g of food). After this habituation period, when free to choose, 3 rats out of 4 preferred eating the piquant chow. In a second series of experiments the rats had access to a choice of chows without any habituation period. In this series, the choice between piquant and nonpiquant chow showed that 4 rats out of 5 preferred to eat the chow without capsaicin. The present experiment shows that the piquant chow eaten by rats produced a fall in rectal temperature 48 h later. The present experiment provides some evidence that rats accustomed to eat piquant food manifested, when free to choose, a preference for an innately unpalatable piquant chow.

Animals↗

PubMed1987

Thermoregulatory behaviour induced by intrathecal injection of substance P in the rat.

A climatic chamber at an ambient temperature (Ta) of 20 and 30 degrees C was used to examine the effect on thermoregulation in the rat of substance P (SP) injected into the lumbar subarachnoid space via a chronic indwelling catheter. In the first series of experiments, the rats had no access to the lever in the climatic chamber. At Ta of 20 degrees C, intrathecal (IT) injections of SP or saline had no effect on body temperature. In the second series of experiments, the rats had access to the lever which actuated a fan that drew cool outside air into the chamber. At Ta 20 and 30 degrees C, IT injection of SP stimulated the activation of bar-pressing to obtain air for cooling. This behaviour was more evident when Ta was 30 degrees C. Under similar conditions, IT injection of saline did not activate bar-pressing. These findings suggest that spinal cord SP receptors may be involved in the control of body temperature.

Animals↗

PubMed1987

Effects of intrathecal capsaicin on autonomic and behavioral heat loss responses in the rat.

Capsaicin and Tween 80 were injected into the lumbar subarachnoid space of rats via a chronic cannula, and the thermoregulatory effects compared. The rats were placed in a climatic chamber at an ambient temperature (Ta) of 20 and 30 degrees C. In the first series of experiments the rats had no access to the fan lever. Intrathecal (IT) capsaicin injection produced a fall in rectal temperature, with a rise in cutaneous temperatures due to vasodilation. On the contrary, IT or the intraperitoneal (IP) Tween 80 injection route had no effect on body temperature. In addition capsaicin-administered IP induced a fall in spinal cord temperature (Tsp). In the second series of experiments the rats had access to a lever activating a fan that drew cool outside air into the climatic chamber. After IT capsaicin injection, the rats increased bar-pressing behavior for fresh air. This was significant at both Ta 20 and 30 degrees C. The results tend to support the hypothesis of capsaicin action somewhere on the thermal afferent pathways. Furthermore, it is possible that the action of capsaicin on thermoregulatory behavior is mediated by the release of substance P from primary afferent terminals.

Animals↗

PubMed1985

Modifications involved in brain glycoconjugate metabolism induced by neonatal capsaicin treatment.

Neonatal capsaicin treatment induces significant changes in rat brain glycoconjugate metabolism. All glycosyltransferase activity involved either in glycoprotein or glycolipid biosynthesis was strongly enhanced. Higher enzymatic activities were obtained when capsaicin-treated rats (T1) had received an additional capsaicin dose (T2). In this case, the fucosyl and galactosyltransferase activities were markedly increased. However, the enhancement of sialyltransferase activity only affects the biosynthesis of glycoproteins and is not correlated with a significant change in ganglioside content. The present results suggest that the modulation of the microsomal glycosyltransferase activity, after capsaicin treatment, could not be stated up through a direct lipid interaction or a change in membrane properties because the phospholipid brain content is not significantly modified.

Animals↗

PubMed1984

Skin or hypothalamus cooling: a behavioral choice by rats.

Rats were chronically implanted with a hypothalamic thermode. After recovery the thermode was heated and the rats were exposed to 4 ambient temperatures (Ta) 20, 30, 35 and 40 degrees C. For each Ta they were subjected to 3 conditions: (1) they could press a bar which provided them with a cool wind; (2) they could press a bar which cooled the hypothalamic thermode; and (3) both bars were active and the rat could press either one. Skin, hypothalamic, and rectal temperatures were recorded at the same time. The results indicate that when rats had either only or by choice access to the lever that cooled their hypothalamus, they used it in such a way as to prevent their hypothalamus from overheating. A lower priority was given to the maintenance of skin temperature.

Animals↗

PubMed1984

Intrathecal chronic catheterization in the rat.

This article describes the fixing of intrathecal cannula to the processus transversus T1. This method of fixing prevents rejection and allows the use of chronic cannula for experiments on animals over long periods up to one year. The intrathecal implantation may be made caudally from T1 using cannula from 1 to 7.5 cm. The technique for repeated perfusion in the freely behaving rat is described.

Animals↗

PubMed1983

Behavioural responses to hypothalamic cooling and heating in the rat.

Rats with hypothalamic thermodes had their hypothalamus cooled or warmed for short sessions. In a first series of experiments, rats could bar-press to obtain fanning with cool air. Cooling the hypothalamus did not suppress or inhibit this behaviour although rectal temperature was markedly increased. In a second series of experiments, bar-pressing would warm the water flowing in the thermode. The rats thus self suppressed the cooling of their hypothalamus. This behaviour was absent at 10 degrees C ambient temperature, and increased with increasing ambient temperature up to 35 degrees C. The result of this behaviour was a small hyperthermia in warm and hot environment compared to control when the rats could not self-suppress the cooling of hypothalamus. The results of both experiments suggest that no conscious direct sensation is aroused by hypothalamic cooling. Hypothalamic heating increased the rat's bar-pressing for cool air and decreased the rat's rectal temperature. When pressure on the lever would suppress a warm hypothalamic stimulus rats self-cooled their hypothalamus, especially in warm environments. Such behaviour resulted in an increased somatic hyperthermia due to the warm environment and hypothalamic cooling. These results are compatible with the hypothesis of a direct conscious sensation from a warm hypothalamus.

Animals↗