Amphetamine psychosis and schizophrenia: A dual model

Several of the behavioral consequences of acute and chronic amphetamine treatment were evaluated and related to the underlying neurochemical correlates of drug treatment. It was suggested that decreased noradrenergic activity after long-term amphetamine treatment influences stimulus sampling, whereas enhanced dopaminergic activity is responsible for the progressive augmentation of stereotypy and self-stimulation behavior observed after long-term exposure to amphetamine. It was hypothesized that amphetamine-induced psychosis and the symptomatology associated with schizophrenia are related to alterations in both norepinephrine and dopamine activity.     

Intracranial self-stimulation in mice using a modified hole-board task: Effects of d-amphetamine

Mice implanted with stimulating electrodes in the lateral hypothalamus demonstrated reliable selfstimulation rates when given the opportunity to break a photobeam in a modified hole-board task. Selfstimulation rates were enhanced by low dosages of d-amphetamine but were depressed by high dosages. The dose-dependent effects of amphetamine could not be accounted for by changes in exploratory hole-board activity and were discussed in terms of an interaction between the rewarding properties of electrical brain stimulation and the reinforcing properties of amphetamine administration.     

Structure of HrcQB-C, a conserved component of the bacterial type III secretion systems

Type III secretion systems enable plant and animal bacterial pathogens to deliver virulence proteins into the cytosol of eukaryotic host cells, causing a broad spectrum of diseases including bacteremia, septicemia, typhoid fever, and bubonic plague in mammals, and localized lesions, systemic wilting, and blights in plants. In addition, type III secretion systems are also required for biogenesis of the bacterial flagellum. The HrcQ_B protein, a component of the secretion apparatus of Pseudomonas syringae with homologues in all type III systems, has a variable N-terminal and a conserved C-terminal domain (HrcQ_B-C). Here, we report the crystal structure of HrcQ_B-C and show that this domain retains the ability of the full-length protein to interact with other type III components. A 3D analysis of sequence conservation patterns reveals two clusters of residues potentially involved in protein–protein interactions. Based on the analogies between HrcQ_B and its flagellum homologues, we propose that HrcQ_B-C participates in the formation of a C-ring-like assembly.     

Abatement of stimulus perseveration following repeated d-amphetamine treatment: Absence of behaviorally augmented tolerance

Acute administration of d-amphetamine results in animals perseverating between two compartments when placed in a free running Y-maze exploratory situation. Experiment 1 indicated that perseverative behavior was attenuated by making the arms of the maze distinctively different. Experiments 2 and 3 demonstrated that repeated amphetamine treatment reduced stimulus perseveration. Drug-induced locomotor activity and stereotypy were not affected by chronic drug administration. The course of the tolerance effect was not altered by pairing the repeated drug experience with Y-maze exposure. It was concluded that although stimulus factors are involved in the perseverative response, conditioning factors are not of primary relevance in determining the tolerance. It was also suggested that the mechanisms which subserve stimulus perseveration are different from those which mediate locomotor activity and stereotypy.     

Potentiation of d-amphetamine and l-dopa-induced acoustic startle activity after long-term exposure to amphetamine

The startle response to an auditory atimulus was potentiated by treatment with d-amphetamine sulfate. Administration of l-dopa after pretreatment with the extracerebral decarboxylase inhibitor MK-486 also increased startle activity. After long-term exposure to amphetamine the startle response to l-dopa and d-amphetamine was enhanced. These findings are consistent with the consequences of longterm amphetamine administration on other amphetamine-induced behaviors (e.g. stereotypy), and are discussed in terms of the effects of long-term amphetamine treatment on pre-and postsynaptic dopamine receptors and serotonin.     

Myocardial infarction after esophagectomy for esophageal cancer: A systematic review

European Surgery - Esophagectomy remains the most effective treatment modality for esophageal cancer. However, esophagectomy is associated with several postoperative complications, including...     

Evidence for a relationship between amphetamine sensitization and electrical kindling of the amygdala

Several schedules of long-term amphetamine administration were evaluated on the development of kindling from the amygdala. Consistent with earlier work involving the effects of chronic exposure to stimulant drugs, withdrawal from chronic amphetamine treatment had little or no effect on kindling. Facilitation of kindling was observed, however, under several schedules of drug treatment. The synergism between amphetamine and kindling was evident during drug schedules in which animals were maintained on drug treatment during the kindling procedure. Under these conditions, the facilitating effects of repeated amphetamine treatment varied as a function of prior experience with the drug. Our findings indicate a relationship between processes involved in amphetamine sensitization and kindling. These data have implications in relation to behavioral observations involving the development of postamphetamine depression during drug withdrawal, and amphetamine sensitization after drug challenge.     

Shock-induced locomotor excitation following acute and chronic amphetamine treatment.

Foot-shock, which ordinarily reduced locomotor activity in mice, enhanced the locomotor excitation produced by d-amphetamine. Moreover, the extent of the foot-shock excitation became progressively more pronounced with successive shock presentations. Although a competitive relationship was demonstrated between the temporal changes in amphetamine-induced locomotor activity and stereotypy. the occurrence of the post-shock excitation was independent of these behaviors. Reduction of norepinephrine and dopamine by pretreatment with α-MpT antagonized the amphetamine effects on all three behaviors. In contrast, reduction of norepinephrine by FLA-63 had no effect on locomotor activity, increased stereotypy to a limited extent, and produced a small but significant decline in the post-shock excitation. Finally, the effects of chronic amphetamine administration on the post-shock excitation paralleled the effects produced by FLA-63, and appeared to be independent of changes in general locomotor activity and stereotypy following chronic exposure to the drug. Results were discussed in terms of the role of norepinephrine and dopamine in mediating these behaviors.