Louis Shuster

Sensitization to cocaine stimulation in mice

Repeated administration of cocaine to B6AF1/J mice increased their running response to 20 mg/kg cocaine as much as four-fold over the response to the first injection. After four daily injections, the extent of the increase was proportional to the dose of cocaine that was used for pretreatment. Sensitization persisted for as long as 2 months after the last injection of cocaine. Cocaine-pretreated mice did not show an increased running response to either morphine or d-amphetamine. The response to cocaine was increased two-fold by treatment with morphine, and three-fold by pretreatment with d-amphetamine. Pretreatment with either imipramine or reserpine did not produce sensitization to cocaine. There was no correlation between cocainesensitization and whole-brain catecholamine levels. There were marked differences in both the running response to cocaine and the extent of cocaine sensitization between the parental strains, C57B1/6J and A/J. Experiments with recombinant-inbred lines, derived from C57Bl/6By and BALB/cBy mice, suggest that the initial response to cocaine and the development of sensitization are controlled by different genetic determinants.

Opiate receptors in mice, genetic differences.

The concentration of opiate receptors in the brains of mice was determined by means of a naloxone-binding assay. The strains of mice used in these experiments were C57BL/6By, BALB/cBy, their reciprocal F1 hybrids, and 7 recombinant-inbred strains derived by inbreeding from the F2 generation. These strains could be divided into 3 groups on the basis of the number of opiate receptors: high (CXBH); low (CXBK); and intermediate (all the other strains). The difference in stereospecific binding of naloxone reflects a difference in the total number of receptor sites rather than in the affinity for the drug. The recombinantinbred strains also differ in their analgesic response to morphine, as previously determined by the tail-flick assay. The differences in the number of opiate receptors are not enough to account for the genetic difference in analgesic responsiveness. Both these parameters appear to be under different genetic control, and at least 2 genetic determinants may be involved in regulating the level of opiate receptors.

Cocaine-induced hepatic necrosis in mice—The role of cocaine metabolism

Abstract Liver damage following cocaine injection in mice is due to the action of a metabolite of cocaine rather than of cocaine itself. The bioactivation of cocaine to a toxic metabolite appears to be a multi-step process, and is carried out by the cytochrome P-450 microsomal mixed function oxidase system. Inhibitors and inducers of this system blocked or potentiated liver damage respectively. Norcocaine was found to be more potent than cocaine, but also required further metabolism for hepatotoxicity. Inhibition of esterase activity increased damage from both cocaine and norcocainee. Most metabolites and analogues of cocaine were not hepatotoxic, indicating fairly strict structure requirements for activation. N -Hydroxynorcocaine, a possible metabolite of norcocaine, was also hepatotoxic. However, it too required further metabolism in order to produce liver damage. Glutathione in the liver was depleted after cocaine or norcocaine by 25–30 per cent at 1 hr after injection. Cysteine pretreatment offered protection from cocaine. These results suggest that an active metabolite of N -hydroxynorcocaine may be responsible for the liver damage observed after injection of cocaine into mice.

A Single-Blinded Case-Control Study of Memantine in Severe Obsessive-Compulsive Disorder

Background: Obsessive-compulsive disorder (OCD) is a common debilitating psychiatric illness that typically improves but does not remit with first-line medication and behavioral treatments. Serotonergic agents including selective serotonin reuptake inhibitors and clomipramine have provided the mainstay of OCD medication management for decades. Combined dopamine/serotonergic agents such as atypical antipsychotics are presently the only OCD-augmenting strategies proven effective via randomized controlled trials. Despite increasing evidence for a pathogenic role of glutamate in OCD, no controlled trials of glutamatergic augmenting agents have been reported. Methods: An intent-to-treat sample included 44 subjects receiving standard treatment at the McLean/Massachusetts General Hospital Intensive Residential Treatment (IRT) program, 22 of whom also received memantine augmentation. Admission, monthly and discharge measures of OCD, depression, and psychosocial functioning were collected by raters blinded to augmentation status. Matched controls were selected based on sex, initial OCD severity, psychosocial functioning, and timing of admission. The Clinical Global Improvement Scale captured global clinical change. Results: Mean (SD) Yale-Brown Obsessive Compulsive Scale score decreases were 7.2 (6.4) among the cases and 4.6 (5.9) among the matched controls, reflecting mean clinical improvement among the cases (27.0% decrease) but not the controls (16.5% decrease). Mean (SD) depression severity score decreases were 5.8 (9.5) among the cases and 4.7 (9.9) among the controls. Initial intrusive obsessions were significantly more severe among marked responders compared with limited response or nonresponse cases (4.4 vs 2.9; t = 2.15; P = 0.048). Conclusions: This study provides preliminary supportive evidence for the effectiveness of memantine as a glutamatergic augmenting agent in severe OCD. Future randomized double-blind placebo-controlled trials are warranted.

A genetic analysis of the response to morphine in mice: Analgesia and running

Two progenitor strains, BALB/cBy and C57BL/6By, their reciprocal F1 hybrids, and seven of their recombinant-inbred derived lines were used to examine the genetic basis of the response to thermal pain, and morphine analgesia at doses of 2.5, 5.0 and 10.0 mg/kg. Both the latency of response to thermal pain and the analgesic response differed significantly among the various strains tested. Strong genetic determinants appear to control their responses. Analyses of the data did not permit clarification regarding the linkage of these determinants. Photoelectric activity cages were used to test the running response of the same strains to 12.5, 25 and 40 mg/kg morphine sulfate. The genetic determinants for running activity were different from those for analgesia. There is clear evidence for two or more loci controlling the behavior at 60 and 75 min after injection, but not enough information to define the loci involved.

Liver damage from cocaine in mice.

Abstract Four daily injections of 20 mg per kg cocaine hydrochloride into B6AF1/J mice produced focal necrosis of liver parenchymal cells in the midzonal region. Massive liver damage and marked elevation of serum glutamic-oxaloacetic transaminase was observed after a single injection of 50 mg per kg cocaine-HC1. This damage led to increased sleep time after pentobarbital, and a decreased rate of pentobarbital metabolism in vivo .

A canine chromosome 7 locus confers compulsive disorder susceptibility

of these receptors may lower dopamine content in the brain and increase the size of the striatum as seen in experimental animals and humans treated chronically with neuroleptics. As previously proposed, a hypodopaminergic state may also mediate the increase in the size of the striatum seen in chronic drug users. In conclusion, our findings highlight the negative consequences of PEMCS on the brain and behavior of adolescence and suggest that the a6 nAChR subunit may modify, at least in part, these effects.

Changes in 3′-nucleotidase during the germination of wheat embryos☆

Abstract When isolated wheat embryos were germinated on nutrient agar there was an 80-fold increase in the specific activity of 3′-nucleotidase, but little change in the activity of nonspecific phosphatase. This increase could not be attributed to the disappearance of an inhibitor, formation of an activator, or conversion of a proenzyme. Changes in 3′-nucleotidase were also measured in different parts of the whole wheat seed. While there was an increase in the total 3′-nucleotidase activity of germinating seeds and embryos, no evidence could be obtained for repression or derepression of the synthesis of this enzyme by its substrates or products. The effect of some growth regulators and the folic acid antagonist amethopterin on increases in 3′-nucleotidase were examined. The use of isolated embryos seems to offer certain advantages over intact seeds in the study of some of the enzyme changes which take place during germination.

The effect of diet on cribbing behavior and plasma β-endorphin in horses

Five cribbing horses and six control horses were used in a latin square design dietary study to investigate the effects of different diets on the frequency of cribbing behavior and plasma levels of beta-endorphin in the horse. Feeding grain or sweetened grain rations was found to cause a significant increase in the cribbing frequency whereas alfalfa pelleted hay was without significant effect on the frequency of the behavior. Baseline beta-endorphin levels in cribbing horses were half those of the non-cribbing controls and remained signif- icantly lower during the feeding trials. These results are discussed as they apply to treat- ment of cribbing horses and in terms of the underlying mechanism of cribbing.

Naloxone injections into the periaqueductal grey area and arcuate nucleus block analgesia in defeated mice.

In a situation of social conflict, mice that are defeated by an opponent exhibit a marked analgesia. Microinjections of naloxone (1 or 10 μg) into the periaqueductal grey area (PAG) or into the region of the arcuate nucleus prior to the defeat prevented the emergence of analgesia. Microinjections of morphine (5 μg) into these sites had previously been shown to produce profound analgesia. Mice whose adrenals were removed rapidly developed analgesia when attacked by a stimulus animal. Injection of naloxone into PAG also antagonized defeat-induced analgesia in adrenalectomized mice. These observations indicate that sites and processes in the brain rather than in the periphery are responsible for the development of analgesia in mice that are subjected to social defeat.