Caffeine reinforces flavour preference in caffeine-dependent,but not long-term withdrawn,caffeine consumers

Rationale. Previous studies have shown that caffeine can reinforce flavour liking in overnight deprived moderate caffeine consumers (e.g. average of 250 mg/day) but not in low consumers (<120 mg/day). However, it is not possible to determine whether the difference between moderate and low caffeine consumers results from pre-existing individual differences in response to caffeine, or results directly from the different amounts of caffeine they habitually consume. If the former were true, then moderate consumers who are completely withdrawn should still manifest the flavour conditioning effect. Conversely, if the latter were true, consumers who are completely withdrawn should not manifest the effect. Objectives. To examine whether moderate caffeine consumers who have been fully withdrawn from caffeine manifest the flavour conditioning effect. Methods. In a double-blind study, 48 moderate caffeine consumers refrained from consuming caffeine for 4 weeks and were given replacement drinks to consume, which were either caffeinated (maintained group) or decaffeinated (withdrawn group). In the final 2 weeks, all subjects evaluated a novel drink containing either 100 mg caffeine or placebo on four non-consecutive days. Results. The rated pleasantness of the novel drink containing caffeine increased over the four test days in the group maintained on caffeine, but pleasantness of the same drink fell significantly in the withdrawn group. Conclusions. These data suggest that the ability of caffeine to reinforce changes in flavour liking are driven by the alleviation of withdrawal symptoms among habitual caffeine consumers and provide further support for the negative reinforcement theory. Electronic Publication     

Clinical Characteristics and Treatment Responses in Cases Diagnosed as Reactive Attachment Disorder

The aim of our study is to report the relation between pathological care and impairment in social interaction, communication, language development, and stereotypical behaviors. Fifteen cases (9 boys, 6 girls) who have the symptoms listed above and who were misdiagnosed with pervasive developmental disorder (PDD), were referred to our clinic for evaluation and treatment. After the cases were evaluated by a semi-structured interview, symptoms related to pathological care were fortified; maternal depressive symptoms associated with child neglect and overexposure to television viewing. The cases and the mothers/primary caretakers were treated in a standardized psycho-educational program of 3 months. After this period improvements were observed in all of the symptom clusters. Twelve cases (80%) had improvements in eye contact. Eleven cases (73.3%) began to engage in reciprocal play and ten cases (66.6%) showed social imitative behaviors. Six cases (40%) began to form sentences. Stereotypic behaviors diminished in six cases (40%) and disappeared in nine cases (60%). According to our findings, although the symptoms of PDD and reactive attachment disorder (RAD) resemble each other, presence of pathological care and good response to treatment in RAD can be important for the differential diagnosis with PDD.     

A novel effect of MPTP: the selective suppression of paradoxical sleep in cats

We studied the effect of MPTP on sleep-wakefulness cycle in cats. Five mg/kg n-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was administered i.p. for 5 consecutive days. Electrocorticographic, electrooculographic and electromyographic recordings were performed before (5 days), during (5 days) and after (14 days) the treatment. Total selective paradoxical sleep deprivation was observed from the first injection. This effect lasted 6-9 days after the last dose, while the relative amount of slow wave sleep increased. The Berg-Fourier analysis showed no significant change in the EEG power spectra of slow-wave sleep during the paradoxical sleep deprivation compared to control period. Recurrence of paradoxical sleep was parallel to the disappearance of the motor symptoms. Histopathological investigation showed neuronal loss mainly in the substantia nigra. Our present study suggests a complex behavioral effect of MPTP.     

Effects of methamphetamine on fixed-ratio responding of food satiated and food deprived rats

After the initial training of the lever pressing response for sweetened condensed milk, rats were put on different fixed-ratio (FR) schedules of reinforcement under conditions of being food satiated and food deprived. Doses of methamphetamine ranging from 0.125 to 1.0 mg/kg were tested in these rats for effects on response rates. Response rates of the satiated rats at the higher FR requirements were slower than those of the deprived rats. At the doses of methamphetamine used, the satiated animals responded at slower than their control response rates and the deprived rats tended to respond faster than control rates.     

Ethanol self-administration in water satiated rats

The effects of water deprivation on acquisition of oral ethanol-reinforced responding by rats were studied. Rats previously trained to lever press for water responded for oral ethanol (8% W/V) as readily when water satiated as when water deprived. Though water deprivation was initially associated with high ethanol intake, on subsequent water satiation ethanol intake was comparable. The effects of Fixed-Interval (FI) schedules of ethanol reinforcement were also studied. The portion of the session occupied by ethanol-reinforced responding varied directly with FI parameter value. The volume of ethanol consumed varied inversely with FI value.     

Self-starvation: A problem of overriding the satiety signal?

Rats housed in either activity wheels or standard laboratory cages received access to food either ad lib or for one 60-min, two 30-min, or four 15-min periods per day. Imposition of restricted feeding schedules led to reductions in food intake and body weight which were greater for animals with access to activity wheels. Increases in activity reflected the percent of body weight loss, which varied directly with frequency of food access. Subsequent recovery of intake was facilitated by partitioning total feeding time into briefer but more frequent periods. In the most extreme frequency-of-access condition, animals with access to running wheels failed to recover from the reduction of intake incurred by imposition of the restricted feeding schedule, even though their total feeding time was the same as that of animals that did recover. These data indicate that self-starvation is not induced by activity per se but results from a general failure to recover intake which, in turn, results from a failure to override the satiety signal within a meal.     

Brief communication effects of estradiol on feeding and locomotion in REM deprived rats.

Ovariectomized female rats were deprived of REM sleep by being confined to 6.5 cm platforms surrounded by water for 96 hr. Stress controls were emersed in water 1 hr/day. Exogenous estradiol benzoate (5 μg/day) stimulated activity and reduced feeding significantly more in stress and normal controls. On the assumption that REM sleep helps maintain catecholamine functioning in the brain, the data are discussed in terms of estradiol influencing weight regulatory behavior through brain catecholamines.     

On the combined effects of amphetamine and food deprivation: A reply to Gollub and Mann

Summary A previously reported interaction of amphetamine and food deprivation on food consumption recently has been called spurious on the basis of a floor effect interpretation of the data, i.e., a complete cessation of eating with the larger doses. A further consideration of the original data indicates (1) such a floor effect does not describe accurately the action of the larger doses, and (2) even the action of the dose that comes closest to satisfying this condition does not in itself explain satisfactorily the interaction. However, analysis of the original data in terms of one additional derived measure of feeding did not yield a statistically significant interaction between amphetamine and food deprivation. The importance of a choice of feeding measure as well as techniques of drug administration and deprivation to such an interaction were briefly considered.Collection of the data reported in this study was undertaken during the author's tenure at Claremont Graduate School, Claremont, California and was supported by U.S.P.H.S. Grant No. MPM-16,441.     

Independence of the effects of d-amphetamine and food deprivation or body weight on the food consumption of rats

Two experiments studied the combined effects of absolute doses (milligrams per rat) of d-amphetamine with either food deprivation (Experiment I) or body weight (Experiment II) on the food consumption of rats. In the first experiment, each of 16 rats was tested once under every combination of three levels of food deprivation (0, 12, and 24 h) and three levels of drug (0, 0.33, and 1.0 mg per rat). Food consumption was measured over 2.5-h sessions that began 30 min after injection. Increasing doses of d-amphetamine and decreasing levels of food deprivation both decreased food consumption, but the effects of the two variables were additive with nonsignificant interaction.In the second experiment, four groups of four rats each, differing in age and body weight, were studied. Under 48-h food deprivation, each rat received each of four doses of d-amphetamine (0, 0.27, 0.54, and 0.81 mg). Food consumption was measured over a 2.5-h period that began 30 min after injection. Increasing doses of d-amphetamine and decreased body weights decreased food consumption, and the combined effects of these two variables were additive. The lack of an interaction between dose and differing body weights in these experiments indicates that the generally-accepted mode of administering d-amphetamine, as milligrams per kilograms of body weight, does not equate rats of differing body weights.This reserch was supported by USPHS reserch grant MH-01604 from the National Institutes of Mental Health. We thank Smith, Kline and French Laboratory for supplying the d-amphetamine used in this study. Robert C. MacPhail is now at the Department of Pharmacology, The University of Chicago, Chicago, Illinois 60637.     

No evidence for latent learning of liking for flavours conditioned by caffeine

RATIONALE: The ability of caffeine to condition liking for flavours depends on the caffeine deprivation status of subjects; however, it is not known if a latent liking for a flavour can be acquired in an undeprived state, which subsequently emerges when consumers are caffeine deprived. OBJECTIVES: To determine if exposure of undeprived caffeine consumers to a novel drink containing caffeine leads to increased liking for this drink when they are subsequently tested when caffeine-deprived. METHODS: In a double-blind placebo controlled study, four groups of 13 moderate caffeine consumers evaluated a novel flavoured drink on 5 days. The test group consumed this drink with 100 mg caffeine when undeprived on days 1-4, and in a deprived state on day 5. Three control groups had the same conditions on all 5 days, with an undeprived group receiving the caffeinated drink, and two deprived groups receiving the drink with caffeine or placebo. RESULTS: The pleasantness of the drink did not change over the 4 training days in the test group, and did not alter when this group was tested when caffeine-deprived. At no stage did these ratings differ between the test and undeprived control groups. Pleasantness increased significantly over the 5 days in the deprived group who received caffeine, and decreased in the deprived group who received placebo. CONCLUSIONS: These results suggest that repeated pairing of a novel flavour with the effects of caffeine in subjects who are not caffeine deprived does not lead to an emergent liking for that flavour when subsequently tested caffeine-deprived. However, the pleasantness of the same caffeinated drink increased if it was consumed when caffeine deprived.