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Biomedical subjects

G Singer

Publications and source records attributed to G Singer.

At least 91 records · Page 5Linked to original sources
PubMed1980

The interaction of a fixed time food delivery schedule and body weight on self-administration of narcotic analgesics.

Experiment 1 reported the effects of the interaction of a fixed 1 min delivery schedule and body weight, using schedule-induced self-injection paradigm, in the rate of acquisition of methadone and heroin. Eighty-one rats were assigned to 100% and 80% reduced body weight conditions with and without a schedule. The findings show that: (a) voluntary heroin and methadone intake was enhanced when a schedule was introduced to animals at 80% but not at 100% body weight; (b) high intake of heroin and methadone was accompanied by increased levels of plasma 11-OHCS. Experiment 2 showed that the high rate of self-injection was due to the interaction of pharmacological properties of opiates and environmental variables rather than to a general increase in activity arising from the deprivation state or the effects of the schedule. The results are discussed in terms of a stress factor arising from an interaction between environmental and pharmacological factors.

Analgesics, Opioid↗
PubMed1980

The effects of several barbiturates on lithium chloride induced taste aversion.

The effects of single doses of five barbiturates on LiCl induced saccharin aversion were examined. Twenty three hour fluid deprived rats were offered a novel 0.125% saccharin solution and then were injected with either 3.0 mEq/kg LiCl or 0.9% saline. On the first test day after conditioning the animals were injected with either 60 mg/kg sodium phenobarbital, 80 mg/kg sodium barbital, 30 mg/kg sodium amobarbital, 20 mg/kg sodium secobarbital, 9 mg/kg sodium pentobarbital or 0.9% saline, 15 min prior to the drinking session. Results indicate that only 9 mg/kg pentobarbital, 60 mg/kg phenobarbital, and 80 mg/kg barbital were effective in attenuating the LiCl induced saccharin aversion on the day of administration. In addition, dipsogenic effects for only 60 mg/kg phenobarbital and 30 mg/kg amobarbital were observed in the saline treated control groups. A synergistic interaction between the effects of LiCl and sodium phenobarbital, barbital, and secobarbital was also observed. Lithium chloride plus these barbiturates resulted in a longer term aversion to saccharin than LiCl alone and no barbiturate produced saccharin aversion when administered without LiCl.

Animals↗
PubMed1980

The taste aversion induction properties of two long duration barbiturates.

The ability of sodium phenobarbital (60 mg/kg) and sodium barbital (80 mg/kg) to produce a taste aversion in 23 hr fluid deprived rats was examined using a discrimination or two bottle taste aversion task (0.125% sodium saccharin solution or water). The interaction of both barbiturates with the effects of 3.0 mEq/kg lithium chloride (LiCl) was also examined. Results indicate that phenobarbital treatment alone produces a stronger saccharin aversion than does barbital. Also, barbiturate treatment 24 hr after LICi administration does not attenuate saccharin avoidance, although phenobarbital treatment following LiCl administration was sufficient to induce a maximum aversion that did not extinguish after twenty days of continuous discrimination testing. These data suggest that the aversion inducing properties of the two barbiturates are dissimilar and that phenobarbital is the more effective agent in the production of saccharin aversion. In addition, barbiturate induced attenuation of conditioned taste aversion is apparently related to the periodic forced intake test model since it does not occur when a water and saccharin choice is available.

Animals↗
PubMed1980

Effects of body weight levels on cannabis self-injection.

Previous findings have shown that naive rats self-inject IV delta 9-THC 12.5 microgram/kg/infusion in the presence of a FT-1 non contingent food delivery schedule. In the present study the effects of three different body weight levels, 80%, 90% and 100%, with and without a FT-1 food delivery schedule, were examined on the THC self-injection behavior. Results confirmed that 80% body weight plus the FT-1 schedule condition leads to the highest intake of THC. In a further experiment, naive rats acquired THC self-injection at 80% body weight with a FT-1 schedule. Rats were then allowed to regain body weight to their free feeding level and were tested again in the same basic paradigm. Animals recovering body weight did not maintain the self-injection rates. The data indicate that the environmental conditions necessary in the acquisition phase are also required to maintain intake of THC 12.5 microgram/kg/infusion.

Animals↗
PubMed1980

The effect of schedule removal on the maintenance of heroin self-injection.

The present study investigated the effect of schedule removal on the maintenance of heroin self-injection in 80% reduced body weight Wistar rats. During the acquisition phase, 42 animals were subjected to a fixed time 1 min food delivery schedule and were allowed to self-inject either heroin or saline for 10 days. During the maintenance phase (Days 11-15), animals in both the heroin and saline conditions were randomly allocated to schedule, no schedule, and no schedule plus food groups. Infusion rates, hot plate response latencies, and food intake were used as dependent measures to monitor differences between groups. The results revealed that schedule removal disrupted, but did not extinguish, heroin-seeking behaviour.

Animals↗
PubMed1980

Food and water deprivation: changes in rat feeding, drinking, activity and body weight.

Groups of male rats totally food deprived for periods up to 96 hr, water ad lib do not totally regain body weight lost through deprivation. Degree of body weight defence was estimated by fitting statistically a curve to the predeprivation baseline data and extrapolating the curve over the deprivation and postdeprivation period. From group data, body weight is not fully defended. However, marked individual differences in degree of body weight defence were noted. During food deprivation the daily drinking cycle persists for approximately 48 hr, then a reduction in nocturnal drinking appears. General activity increases but only in the light period. After food restitution, the main hyperphagia is confined to the first post-deprivation day. Additional, subtle long term effects of overeating in the light period are also found. In contrast to food deprived groups, water deprived groups accurately defend body weight. During water deprivation daily food intakes decrease immediately whereas nocturnal activity decreases after approximately 72 hr of deprivation has elapsed. After the termination of water deprivation the immediate response is gross hyperdipsia, but again subtle long term effects are apparent. Total daily food intake increases for many days but the increase is not confined to either light or dark periods. Water intake is similarly affected. These results are evaluated in relation to the notion of a body weight set-point regulating feeding behavior. Some limitations on the value of the findings in terms of species differences and lack of ecological validity are also discussed.

Animals↗
PubMed1979

Hypnotic analgesia in conditions of stress is partially reversed by naloxone.

In this study the hypothesis that hypnotic analgesia under conditions of stress is mediated through a neurochemical mechanism involving the release of opioid peptides in the CNS was investigated. Ten highly hypnotizable subjects participated in a 2 x 2 factorial design, which involved hypnotic analgesia, stress and double blind administration of naloxone (an opiate antagonist) or placebo. Analysis of post-hypnosis results indicates that hypnotic analgesia was significantly reversed by the interactive effects of stress and naloxone. It is inferred that stress may be the common psychological denominator of the various analgesic methods which effectively engage this endogenous pain inhibitory system. Additional analyses of anxiety measures reveals no significant association between trait and state anxiety, but significant relationships between state anxiety and time tolerance to ischemic pain. These results suggest that anxiety remains a definitional problem and that previous conceptualizations may not have satisfactorily explained the affect's adaptive function.

Adult↗
PubMed1979

Interactions between personal expectations and naloxone: effects on tolerance to ischemic pain.

Sixteen healthy subjects participated in an investigation of the interactive effects of naloxone and personal expectations of control, stress, and anxiety, on time tolerance to ischemic pain. Control and anxiety levels provided no significant naloxone-saline discriminations, but there was a significant interaction between stress levels and naloxone-induced reduction in tolerance to ischemia. This finding suggests that activity in the opiate system may be a function of the modifying influences of variable attitudes to environmental stress. A primary analgesic role for the endorphins is challenged, however, by the findings that tolerance levels failed to reveal naloxone reactors and stress levels were not significantly associated with differences in tolerance. The latter, on the other hand, correlated significantly with control and anxiety levels, indicating that further research is needed to clarify the complex relationship between these three variables and their effects on the modulation of pain perception.

Adult↗
PubMed1979

The involvement of interoceptive factors in the maintenance of heroin-seeking behavior.

The role of interoceptive stimuli in conditioned heroin-seeking behavior was investigated using forty-two naive male Wistar rats. A 21-day Phase I period in which 28 animals self-injected heroin in saline solution was followed by a 5-day Phase II period in which 7 animals were allowed access to the original solution; 7 animals were allowed access to saline only; 7 animals were allowed access to distilled water; and 7 animals were allowed no access to any solution. Results showed that only the heroin and (heroin-associated) saline groups shows a significant difference in operant rate compared to animals that had been continually exposed to saline only. It was concluded that heroin-seeking behavior was maintained in the (heroin-associated) saline group as a result of physiological conditioning following repeated association of saline with heroin.

Animals↗
PubMed1979

Self-administration of delta 9-tetrahydrocannabinol by rats.

The present study examines the dose-response pattern of delta 9-tetrahydrocannabinol self-injection in naive rats at 80% reduced body weight and 100% body weight, both conditions with a fixed-time 1 min (FT-1) food delivery schedule. The results indicated that food deprived animals tested on a FT-1 min schedule self-injected low doses of delta 9-THC at a higher rate than those animals at 100% body weight and on a FT-1 min schedule. Animals at 80% reduced body weight without a schedule did not differ from rats self-injecting delta 9-THC at free feeding situation. These findings suggest that rats without previous history of drug dependence self-administer low doses of delta 9-THC and that the interaction between the food deprivation state and the environmental contingencies introduced by a FT-1 min schedule is a critical variable in the acquisition period.

Animals↗
PubMed1979

Effects of a fixed time schedule and body weight on ethanol self-administration.

Two experiments are reported. The first study showed that the patterns of ethanol acquisition using the schedule induced self-injection paradigm, are more similar to those of heroin than methadone or nicotine but dissimilar to that of d-amphetamine. The second study showed that ethanol intake once established was not maintained by removal of the schedule. The results also showed that schedule induced behavior may be stressful as indexed by a significant increase of plasma corticosterone levels.

Alcohol Drinking↗