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R Eikelboom

Publications and source records attributed to R Eikelboom.

At least 19 recordsLinked to original sources
PubMed1999

Effects of short- and long-term wheel deprivation on running.

The effects of wheel deprivation on running were explored. Eight male rats, well habituated to wheels, were each deprived of wheels for periods of 0, 1, 3, and 10 h during the night (Experiment 1) and 0, 1, 3, and 10 days (Experiment 2). In Experiment 1, as wheel deprivation lengthened, wheel running in the first 24 h of access increased. After 10 days of wheel deprivation subsequent daily running decreased (by 70%), and feeding was suppressed for several days. This temporary decline may be due to detraining and the rats physical inability to run more. Experiment 3 with 12 rats found that the running increase after 3-h wheel deprivation was proportional to the amount of running normally occurring during the deprivation period. Over the short-term, running appears to be regulated like other appetitive behaviors.

Animals↗
PubMed1997

Alternate-day wheel access: effects on feeding, body weight, and running.

For rats access to a running wheel results in a pronounced but temporary suppression of feeding. The reasons for the feeding suppression and its temporary nature are unclear. The effects of alternate-day wheel access were explored by comparing feeding and running in 25 male Sprague-Dawley rats given either no wheel access, continuous wheel access, or alternate-day wheel access. With alternate-day wheel access food intake was suppressed on wheel days and elevated on non-wheel days for the full 32 days of the experiment. Body weight decreased on wheel days and showed a large increase on non-wheel days. Acquisition of running over days was similar in both wheel groups and plateaued at the same level, but running was elevated, compared to continuous-access rats, for the first few hours when alternate-day rats were returned to the wheel. These results suggest that wheel-induced feeding suppression is not due to the novelty of the wheel and that this suppression can be extended by providing periods with no wheel access. The temporary nature of feeding suppression in chronic access conditions may be due to secondary longer term motivational changes.

Animals↗
PubMed1993

Performance of two films for densitometry of retinal photographs.

The relative performance was determined of two different photographic films (Kodak Panatomic-X and Kodak Technical Pan) for densitometry readings from retinal photographs of patients who had or were suspected of having glaucoma. The raw data from the two films were significantly different. The high contrast film was particularly sensitive to external variables; however, when normalised in terms of the standardised deviation, the data from the two films were comparable (P < 0.005). We also measured the pattern of nerve fibre layer loss using digital image analysis of red-free photographs of normal, ocular-hypertensive, glaucoma-suspect and glaucomatous eyes. Several mathematical techniques were used to characterise the data from each eye and then to compare these data to the mean photographic density of the normal eyes. Results showed that it was possible to separate normal eyes from glaucomatous eyes. The highest sensitivity achieved was 100% for right and 88% for left eyes, and the highest specificity was 100% for both eyes.

Adult↗
PubMed1991

Caffeine-induced place and taste conditioning: production of dose-dependent preference and aversion.

Although caffeine may be the most widely used behaviorally active drug, few studies have examined its rewarding properties. In the present study, the designs of place-conditioning and taste-conditioning paradigms were combined in a single experiment to provide two independent measures of drug reward. During 3 preconditioning sessions, undrugged rats received access to 2 distinctive chambers connected by a small tunnel. During the 8-session conditioning phase, groups were given home cage access to either a sweet or salty solution, administered caffeine (0.3, 1.0, 3.0, 10.0, 30.0 mg/kg IP; 30.0 mg/kg SC), and confined to one of the chambers. On alternate sessions, rats were given home cage access to the remaining solution, injected with the vehicle, and confined to the opposite chamber. On test sessions 1 and 2, undrugged animals were given home cage access to one of the flavored solutions and water, and then allowed access to both conditioning chambers. On test session 3, rats were given access to both flavored solutions, injected with the drug used during conditioning, and again allowed access to both chambers. Caffeine (3.0 mg/kg) produced a significant place preference. The highest dose (30.0 mg/kg IP and SC) produced significant place and taste aversions. A control group given (+)-amphetamine illustrated a significant place preference and taste aversion as expected. Thus caffeine appeared to produce a dose-dependent biphasic effect; a lower dose was rewarding, whereas higher doses produced aversions to environmental stimuli associated with the drug.

Animals↗
PubMed1991

Effects of pimozide on the hedonic properties of sucrose: analysis by the taste reactivity test.

The ability of the neuroleptic agent, pimozide, to modify sucrose palatability was assessed using three 10-min taste reactivity test sessions. Pimozide was found to suppress the ingestive response of tongue protrusions, but enhance the mildly ingestive/neutral response of mouth movements elicited by an intraoral infusion of sucrose solution. Since the pattern of taste reactivity responding shifted from highly ingestive to mildly ingestive/neutral, our results suggest that pimozide pretreatment reduces the palatability of sucrose solution. The temporal pattern of the modification of these taste reactivity responses was predicted by the Anhedonia Hypothesis.

Animals↗
PubMed1989

Wheel running, food intake, and body weight in male rats.

The acquisition of wheel running, its effects on food intake and body weight, and the effects of wheel deprivation, were examined in male rats. Running increased during the first 15 days of access, then plateaued. When wheels were unlocked after 10 days of deprivation, running was reduced, but quickly recovered to original levels. Animals first given wheel access 49 days into the study ran little, with no increase over days. Food intake dropped each time with wheel access, but recovered to control levels over 10-14 days. Wheel deprivation resulted in a temporary hyperphagia. With wheel access, weight initially dropped and was then maintained at a reduced percentage of homecage-housed animals. In male rats wheel access appears to have temporary effects on food intake, and long term effects on weight. Marked differences in the activity of same-age rats suggest that wheel running is in part a function of housing history.

Animals↗
PubMed1988

A microanalysis of wheel running in male and female rats.

The pattern of ad lib wheel running was studied in adult Sprague-Dawley rats. Wheel turns per 20 seconds were recorded for 5 days. Females ran more than males but both ran chiefly at night, with a peak at the beginning and a decline to low levels by daytime. Log-survivor plots showed running occurred in distinct episodes separated by long periods of nonrunning. Both the nightly decrease and the sex difference in running were due to changes in duration of episodes and the running speed. Initiation of running, as reflected in the length of nonrunning periods was similar in both sexes and remained constant over the night. Running was discussed in terms of independent initiation and termination factors and its parallels to eating patterns.

Animals↗
PubMed1988

Acute effects of exercise intensity on appetite in young men.

This study investigated the acute effects of two exercise intensities on three measures of appetite. Fifteen, 12-h-fasted, college-age males completed three experimental sessions in counterbalanced orders: no-exercise control; cycle exercise performed at 35% VO2max; and cycle exercise performed at 68% VO2max. Both exercise conditions involved a total energy expenditure of 4.1 kcal.kg-1 body weight. Dependent measures were intermittent hunger and sucrose palatability ratings, and food intake at a test meal given approximately 1 h post-exercise. Hunger was briefly suppressed in the high-intensity exercise condition compared to low-intensity exercise and control, while intake of liquid-source kilocalories and carbohydrates was higher after the exercise sessions. Total caloric intake remained stable. Sucrose palatability did not vary across sessions. Intensity is inferred to be an important variable mediating exercise effects on appetite. Relations between appetite measures are discussed, and validity of sucrose palatability ratings and common methods of measuring food intake questioned. Exercise, while not decreasing food intake, does not appear to increase it, and the benefits of exercise for body fat reduction are not immediately offset by compensatory caloric intake.

Adult↗
PubMed1987

Naloxone, naltrexone and body temperature.

The temperature effects of naloxone and naltrexone (1-30 mg/kg) were examined in well habituated male rats. These drugs had a similar time course and potency, producing a dose-dependent hypothermia followed several hours later by a hyperthermia. A subsequent study found that not only did 30 mg/kg of naloxone or naltrexone produce an equivalent hypothermia but this hypothermia was just as pronounced during the dark as in the light part of the cycle.

Animals↗
PubMed1987

Feeding induced by ventricular bromocriptine and amphetamine: a possible excitatory role for dopamine in eating behavior.

The effects of intracerebroventricular (ICV) administration of the dopamine (DA) agonists, bromocriptine and d-amphetamine, on feeding and feeding-associated behaviors were examined. Male Wistar rats were injected ICV with 80-micrograms bromocriptine or its vehicle or with 10-micrograms d-amphetamine or saline. For 2 hr, the activity, duration of individual grooming, eating, and drinking bouts, and the amount of food and water consumed were recorded. Bromocriptine and amphetamine significantly increased the amount the animals ate and meal duration, but did not significantly affect the other observed behaviors (grooming, drinking, activity, or number of meals). The findings are interpreted as being consistent with the anhedonia hypothesis (Wise, 1982), in which DA is involved with the reinforcing components of external stimuli (i.e., food).

Animals↗
PubMed1986

Learned anticipatory rise in body temperature due to handling.

Hyperthermia produced by handling becomes evident at the initial daily measurement if temperature is measured at a consistent time. This hyperthermia may be a learned effect occurring in anticipation of handling. In Experiment One male Wistar rats were either unhandled or had their temperatures measured daily in the dark or the light part of the day. All animals had their temperatures measured on Day 29, in the dark. Rats usually tested in the dark were hyperthermic, 38.8 degrees C, relative to rats previously handled only in the light, 38.1 degrees C, and to naive rats, 37.9 degrees C. In Experiment Two rats were handled three times daily in either the light or the dark. On Day 9 each group was divided in two, and temperatures were measured at either the usual time or at the other time. Rats tested at their usual time were hyperthermic, relative to rats normally handled in the other part of the cycle. This suggests a conditioned hyperthermia occurs in response to stimuli predictive of handling.

Animals↗
PubMed1985

Dopamine-beta-hydroxylase inhibitors, feeding and locomotor activity: reinstatement of feeding following central norepinephrine.

The effects of two dopamine-beta-hydroxylase (DBH) inhibitors, FLA-63 and fusaric acid (FA) on feeding behaviour and locomotor activity were examined. In Experiment 1 activity was measured over 7 hr in 48 rats treated with FLA-63 (0, 1.25, 2.50, 5.00 mg/kg) or FA (0, 20.0, 40.0, 80.0 mg/kg). While FA produced no significant effect on activity, FLA-63 produced an increase at the highest doses. In Experiment 2 the same doses of the two DBH inhibitors were administered to 48 rats and food intake over 7 hr was measured; both FA and FLA-63 produced decreases in food intake. In a third experiment, rats were stereotaxically implanted with microinjection guide cannulae extending to the ventromedial hypothalamus and, following peripheral treatment with either 5.0 mg/kg FLA-63, 40 mg/kg FA, or their respective vehicles were injected centrally with morphine (5.3 nmoles in 0.5 microliter), norepinephrine (NE; 60 nmoles in 0.5 microliter for the FLA-63 pre-treated group and 30 nmoles in 0.5 microliter for the FA pre-treated group) or saline. Central NE was found to reinstate feeding only in the hr following injection in both groups, while morphine reinstated feeding only in the FA group and only in the third hr following injection. Results support the involvement of hypothalamic NE in feeding.

Animals↗
PubMed1983

Human pancreas GH-releasing factor analog restores high-amplitude GH pulses in CNS lesion-induced GH deficiency.

Lesions of the ventromedial-arcuate (VMH-ARC) region of the hypothalamus result in impaired growth accompanied by a marked suppression in spontaneous GH secretory bursts. We studied the effects of an analog of the recently characterized human pancreas GH-releasing factor hpGRF(1-40) on GH secretory dynamics in freely-moving chronically cannulated rats bearing electrolytic lesions of the VMH-ARC. Intravenous administration of the hpGRF analog (hpGRFa) caused a dramatic surge of GH within 5 min; plasma GH levels rose to values as high as 2900 ng/ml and remained significantly elevated for 15-30 min post treatment. The simultaneous iv administration of somatostatin-14 and hpGRFa resulted in a significant inhibition of the hpGRFa-induced GH release at 5 min but not at 15 min. These results clearly demonstrate that impaired GH secretion resulting from VMH-ARC lesions can be restored by hpGRF. The findings are promising in that hpGRF and its analogs may provide valuable agents for the diagnosis and treatment of disorders of growth secondary to CNS dysfunction.

Animals↗