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Biomedical subjects

G Singer

Publications and source records attributed to G Singer.

At least 73 records · Page 4Linked to original sources
PubMed1983

The effect of 6-OHDA lesions of the nucleus accumbens septum on schedule-induced drinking, wheelrunning and corticosterone levels in the rat.

In a series of four experiments the relationship between 6-OHDA lesions of the nucleus accumbens septum (NAS), schedule-induced behaviors and plasma corticosterone levels was explored. Data from the first experiment show a significant decrease in water intake during a scheduled food delivery test hour for 6-OHDA lesioned groups of rats compared with sham or non-lesioned groups of rats, while during the remaining 23 hours of the day water intake was the same for 6-OHDA lesioned and sham lesioned groups. In a second experiment similar decreases in schedule-induced wheelrunning were observed for 6-OHDA lesioned rats when compared with sham lesioned rats. Data from a third experiment showed significant increases in plasma corticosterone levels of rats in the presence of a scheduled food delivery compared with rats given non-scheduled food. In a fourth experiment it was shown that 6-OHDA lesions of the NAS abolish this increase of corticosterone levels in rats on a food delivery schedule. These data extend the findings of Robbins and Koob [19] and show a more general involvement of the dopaminergic pathways of the NAS in schedule-induced behaviors and in concomitant plasma corticosterone changes.

Animals↗
PubMed1983

The suppression of ethanol self injection by buprenorphine.

The schedule induced self-injection procedure was used to establish ethanol self-injection in 16 rats. Pretreatment with an injection of 0.3 mg/kg buprenorphine significantly reduced ethanol self-injection in a group of 8 rats. This effect was not found in a second group of 8 rats which received saline pretreatment. The findings provide support for an involvement of buprenorphine, in ethanol self-injection, which cannot be explained in terms of opiate induced shifts in taste preference. From the present data it cannot be determined whether the agonist or antagonist opiate properties of buprenorphine cause the blocking effect.

Alcohol Drinking↗
PubMed1983

A reinterpretation of schedule-induced behaviors based on a systematic analysis of behavior.

Confusion exists regarding the criteria to be used in determining whether or not particular behaviors are schedule-induced. Four critical characteristics of schedule-induced behaviors are suggested and a comparison made of the complete range of behaviors exhibited by body weight-reduced rats drinking in response to one of three stimuli. These were (1) a fixed-time food reinforcement schedule, (2) a meal of dry food, and (3) 24 hour water deprivation. Drinking, locomotion, rearing and oral and perioral behaviors occurred in accordance with the defining characteristics of schedule-induced behaviors. Rats in the fixed-time reinforcement condition also deposited significantly greater numbers of fecal boli. Sniffing and food bowl related behaviors occurred as terminal responses for this group. It is concluded that animals which receive reinforcers intermittently maintain high levels of arousal for extended periods, and that the presence of the schedule may mimic conditions experienced by wild rats in non-laboratory settings. In such conditions ambulatory behaviors may be particularly adaptive. In contrast, reinforcing sensory feedback and a stress reducing role may be particularly important in the mediation of oral behaviors (such as drinking) which occur during intermittent reinforcement.

Animals↗
PubMed1983

Effects of interactions between amphetamine and food deprivation on covariation of muricide, consummatory behaviour and activity.

Four experiments were conducted to study covariation of muricide, consummatory behaviour and general activity under conditions involving interactions between food deprivation and anorexia induced by low doses of d-amphetamine. Two basic experimental designs were used: (a) dosage of amphetamine was varied, with duration of deprivation constant at 22 hr; and (b) deprivation was varied, with a constant amphetamine dose of 1.0 mg/kg body weight. In general, effects of both types of manipulation on eating, drinking, general activity, and muricidal behaviour were consistent with earlier reports of effects when either deprivation or amphetamine-induced anorexia was varied separately. Rank order correlations supported the conclusions that relations between muricide, eating behaviour and general activity were both dose and time dependent. However, there also was evidence that such covariations existed for some, but not all, parameters of these behaviours, eg. differences in the median effective doses of amphetamine; differences in threshold doses; and differences in durations of deprivation required to counteract effects of amphetamine. A dissociation of muricide and eating behaviour was strikingly evident when all satiated animals injected with normal saline engaged in muricidal behaviour and when increasing deprivation had no significant influence on carcass consumption or muricidal behaviour of saline treated subjects. The present results are interpreted as essentially inconsistent with concepts in which covariation of muricide and consummatory behaviour is considered to depend: (a) upon a common set of physiological conditions, or (b) upon one being the antecedent of the other. However, results are consistent with a model in which each behaviour has its own basic physiological condition(s) which may be activated concomitantly.

Aggression↗
PubMed1982

Effects of dopaminergic nucleus accumbens lesions on the acquisition of schedule induced self injection of nicotine in the rat.

Data from recent experiments show that dopaminergic depletion of the nucleus accumbens septum (NAS) decreases the frequency of schedule induced drinking and wheel running. In the present experiment a group of 8 rats with 6-OHDA lesions in the NAS showed a significantly lower rate of schedule induced nicotine self injection than sham operated controls. These findings extend the number of schedule induced behaviors which appear to depend for their occurrence on an intact dopamine system in the NAS.

Animals↗
PubMed1982

Intravenous self-administration of acetaldehyde in the rat as a function of schedule, food deprivation and photoperiod.

The present series of experiments were conducted to discover whether rats would self-administer acetaldehyde (AcH) intravenously. The first study establishes the basic parameters for AcH self-injection in rats at 80% reduced body weight on a fixed-time 1 min (FT-1) food delivery schedule tested in the dark phase of a 12:12 light/dark cycle. The results show a dose-dependent effect with 1.3% AcH being the preferred dose as measured by the number of infusions. In the second experiment rats were on 100% free-feeding and at 80% reduced body weight, both conditions either with or without the influence of a FT-1 min schedule. The findings indicate that an interaction between dose, food deprivation and a FT-1 min schedule appears to initiate and maintain high levels of AcH self-injection in the dark. In a further experiment using 1.3% AcH the self-injection rates of animals at 80% body weight with a FT-1 min schedule reveal that the time of day of testing may be an important variable for inducing AcH intake. The results suggest that under altered environmental conditions AcH may have both an aversive and reinforcing effect.

Acetaldehyde↗
PubMed1982

Schedule-induced self-injection of drugs.

Studies of acquisition and maintenance patterns of drug intake, including dependence, necessitate voluntary intake of drugs. Voluntary intake in animal studies is difficult to achieve because of aversive taste factors associated with most drugs, and involuntary or forced choice methods obscure the behavior which is the object of study. The schedule-induced polydipsia paradigm has been used to induce oral ingestion of large volumes of alcohol, barbiturate and other drug solutions. We have developed a method of schedule-induced self-injection which allows the study of acquisition and maintenance of drug intake behavior with changing environments free from the interference of taste factors or imbalances due to excessive water intake. In this paper we review our findings on the acquisition and maintenance patterns of amphetamine, methadone, heroin, alcohol, nicotine, cocaine, delta 9-THC and haloperidol. For all drugs except amphetamine, the combination of schedule and nutritional deprivation leads to the highest rates of drug intake as compared to controls. The schedule does not appear to be a potent factor at 90% and free feeding weight, and drug intake is the result of interaction of environmental factors and pharmacological properties of the drugs, rather than the effects of drug or environmental factors separately. The maintenance patterns of nicotine, cocaine, heroin and alcohol are also discussed and the advantages of schedule-induced self-injection over schedule-induced polydipsia methods are presented.

Amphetamine↗
PubMed1982

Experimental autoimmune encephalomyelitis. An anatomically-based explanation of clinical progression in rodents.

Lactate accumulation was measured soon after decapitation in three adjacent lower spinal cord regions of rats with EAE. Results indicate that during EAE, and in correlation with the onset of clinical signs of both initial attack and short-term relapse, a differential focal increase in lactate accumulation occurs in rat spinal cord compared to Freund's Complete Adjuvant controls, with greater increase occurring in more caudal segments. A [14C]antipyrine method of estimating relative spinal cord blood flow failed to find evidence that the lactate accumulations were due to focal ischemia. Subsequent measurement of isotopic water and total protein increases in the same cord regions indicated that a slight but significant increase in vasogenic edema occurs in correlation with the increase in lactate accumulation and the onset of EAE clinical signs. The data are interpreted as lending support to a speculative theory of paralysis induced by edema during EAE, in which nerve root endoneurium is postulated as the functionally vulnerable site. More specifically, it is hypothesized that the ascending progression of clinical signs of EAE in rodents can be explained on an anatomical basis by progressive disturbance of the nodes of Ranvier in nerve root myelinated fibers.

Animals↗
PubMed1981

Reactions to ischemic pain: interactions between individual, situational and naloxone effects.

Fifty-two paid volunteers participated in two separate factorial investigations of the effects of naloxone on time tolerance of and affective reactions to ischemia, as a function of the interaction between expectations of involvement in the experimental situation and experimental variables involving stress or suggestions of analgesia. Naloxone-induced reduction in tolerance to ischemia interacted significantly with the level of involvement expectancies. The suggestion of analgesia provided no significant naloxone-saline discrimination, but there was a significant interaction between variable memory task conditions and drug effects on the time ischemia was tolerated. These findings suggest that naloxone-opiate receptor interactions may depend on individual differences in attitudes to the situation, but may be potentiated by select environmental stimuli. Analyses of the effects of treatment on affective reactions to ischemia failed to show consistent results.

Adult↗
PubMed1981

Low dose cocaine self-administration by naive rats: effects of body weight and a fixed-time one minute food delivery schedule.

The self-administration rates of four groups of eight rats for low dose cocaine (0.1 mg/kg infusion) under free feeding and 80% body weight conditions, with and without a fixed time 1 min (FT-1) food delivery schedule, were compared with those of saline reinforced animals under the same conditions. Results indicated that (1) overall, self-administration rates were significantly greater for cocaine reinforced animals, (2) significantly higher rates of cocaine self-administration occurred in body weight reduced rats and (3) the operation of FT-1 schedule neither significantly enhanced or inhibited drug intake. In the second experiment, schedule and no schedule conditions were reversed for the sixteen 80% body weight, cocaine reinforced rats. Results showed that reversing schedule and no schedule conditions produced no significant change in drug intake. It was concluded that low dose cocaine self-administration is significantly amplified by body weight reduction.

Animals↗
PubMed1981

Cross self-administration of delta 9-tetrahydrocannabinol and D-amphetamine in rats.

1. Schedule-induced intravenous self-injection of delta 9-tetrahydrocannabinol (delta 9-THC) and d-amphetamine was investigated in the same animals. 2. Rats self-injected significantly more amphetamine than delta 9-THC. However, the results suggested that delta 9-THC did not play a predisposing role to the increased amphetamine intake. When delta 9-THC was reinstated after amphetamine response rates were drastically reduced. 3. It is concluded that the reinforcing effects of delta 9-THC may be unrelated to its stimulant effects. The small number of responses for delta 9-THC is in agreement with reports of the poor reinforcing capability of cannabis compounds in rats.

Animals↗
PubMed1980

[Complications of percutaneous transhepatic cholangiography].

It is reported on complications which appeared in the percutaneous transhepatic cholangiography performed in n = 130. The complications were subdivided into 1. Complications at immediate performance of the intervention. 2. complications which are to be observed in radiology, 3. complications which became conspicuous in the operation which immediately followed the intervention, 4. complications in the observation of the course in non-operated patients, 5. complications by the percutaneous transhepatic cholangiography in an operation which was performed at a later time. There did not appear any severe complications which burdened the intervention, particularly no bilious peritonitides or severe haemorrhages. None of the changes observed led to the interruption of the intervention. The conclusion is drawn that the percutaneous transhepatic cholangiography is a method of the morphological diagnostics of the biliary ducts which is poor in risk.

Cholangiography↗
PubMed1980

[Experience with percutaneous transhepatic cholangiography].

After description of the technical performance of the percutaneous transhepatic cholangiography is reported on experiences with this method. 114 examinations were performed and in 87.6% the bile ducts were described. The result of the percutaneous transhepatic cholangiography confirmed itself in 85% of the patients, in 10% the diagnosis dilated itself according to the result of the operation, and in 5% the diagnosis had to be changed. In 12.4% no biliary duct could be punctured, among them were 10 anicteric patients. The reflux technique described has a high number of impact and a good evidence in the morphological differentiation of the obstruction syndrome. It seems not indicated for anicteric patients. Indications, contraindications and the comparison of the examination method to the ERC are described. The percutaneous transhepatic cholangiography may be used with simple apparative and instrumental means.

Biliary Tract Diseases↗
PubMed1980

Second-site rho mutation: genetic linkage and polyC-dependent ATPase.

Rho has been purified to homogeneity from Escherichia coli double mutant rho-115 sur-38 cells, and from rho6 and rho-115 cells. The sur-38 mutation suppresses the original rho-115 phenotype. We observe that the polyC-dependent ATPases of these three rho preparations have the same specific activities. However, the ATPase of rho from the double rho-115 sur-38 mutant is extremely heat labile, while that from rho-115 shows a heat lability intermediate between the wild type and the double mutant. Transduction analysis suggests that sur-38 is closely linked to rho-115 in the order ilv--sur-38--rho-115--metE. These data are consistent with the model that the sur-38 mutation affects the structural gene for rho.

Adenosine Triphosphatases↗
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↗