Gluconeogenic activity in response to chronic administration of amphetamine sulphate and drug withdrawal

Elevated aspartate and alanine aminotransferase levels and natural death among patients with methamphetamine dependence

BACKGROUND

Methamphetamine is one of the fastest growing illicit drugs worldwide, causing multiple organ damage and excessive natural deaths. The authors aimed to identify potential laboratory indices and clinical characteristics associated with natural death through a two-phase study.

METHODS

Methamphetamine-dependent patients (n = 1,254) admitted to a psychiatric center in Taiwan between 1990 and 2007 were linked with a national mortality database for causes of death. Forty-eight subjects died of natural causes, and were defined as the case subjects. A time-efficient sex- and age-matched nested case-control study derived from the cohort was conducted first to explore the potential factors associated with natural death through a time-consuming standardized review of medical records. Then the identified potential factors were evaluated in the whole cohort to validate the findings.

RESULTS

In phase I, several potential factors associated with natural death were identified, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), comorbid alcohol use disorder, and the prescription of antipsychotic drugs. In phase II, these factors were confirmed in the whole cohort using survival analysis. For the characteristics at the latest hospital admission, Cox proportional hazards models showed that the adjusted hazard ratios for natural death were 6.75 (p<0.001) in the group with markedly elevated AST (>80 U/L) and 2.66 (p<0.05) in the group with mildly elevated AST (40-80 U/L), with reference to the control group (<40 U/L). As for ALT, the adjusted hazard ratios were 5.41 (p<0.001), and 1.44 (p>0.05). Comorbid alcohol use disorder was associated with an increased risk of natural death, whereas administration of antipsychotic drugs was not associated with lowered risk.

CONCLUSIONS

This study highlights the necessity of intensive follow-up for those with elevated AST and ALT levels and comorbid alcohol use disorder for preventing excessive natural deaths.

Amphetamine withdrawal leads to behavioral sensitization and reduced HPA axis response following amphetamine challenge

Withdrawal from repeated amphetamine (AMPH) administration leads to behavioral sensitization following a drug or a stress challenge and is commonly used to model anhedonia in rats, a core symptom of depression in humans. It is proposed that corticosteroids are involved in the mediation of sensitization and depression. The aim of the present study was to investigate stress and AMPH- induced release of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) during withdrawal from an escalating dosage schedule of AMPH known to produce depression-like effects in rats. Wistar rats were given 3 injections (i.p.) per day over 3 days, escalating from 1 mg/kg to 9 mg/kg and a final injection of 10 mg/kg AMPH or saline on day 4. On day 2 of withdrawal, the animals were tested in the Porsolt swim test. HPA axis activity in response to restraint stress was tested on withdrawal day 14 and in response to AMPH challenge on withdrawal day 30. We found no effect of AMPH withdrawal in the Porsolt swim test and on the ACTH or CORT response following restraint stress. AMPH withdrawn animals expressed behavioral sensitization in terms of locomotion and reduced ACTH and CORT plasma levels following a 1 mg/kg AMPH challenge in comparison to the controls. We conclude that there is no critical involvement of a sensitized HPA axis stress response in the long-term expression of behavioral sensitization.

Psychostimulant withdrawal as an inducing condition in animal models of depression

A large body of evidence indicates that the withdrawal from high doses of psychostimulant drugs in humans induces a transient syndrome, with symptoms that appear isomorphic to those of major depressive disorder. Pharmacological treatment strategies for psychostimulant withdrawal in humans have focused mainly on compounds with antidepressant properties. Animal models of psychostimulant withdrawal have been shown to demonstrate a wide range of deficits, including changes in homeostatic, affective and cognitive behaviors, as well as numerous physiological changes. Many of these behavioral and physiological sequelae parallel specific symptoms of major depressive disorder, and have been reversed by treatment with antidepressant drugs. These combined findings provide strong support for the use of psychostimulant withdrawal as an inducing condition in animal models of depression. In the current review we propound that the psychostimulant withdrawal model displays high levels of predictive and construct validity. Recent progress and limitations in the development of this model, as well as future directions for research, are evaluated and discussed.

Methamphetamine differentially regulates hippocampal glucocorticoid and mineralocorticoid receptor mRNAs in Fischer and Lewis rats

Fischer 344 (F344) and Lewis (LEW) rats differ in physiological regulation of the limbic-hypothalamo-pituitary-adrenal (LHPA) axis, such that F344 rats exhibit greater LHPA axis responses to a variety of stimuli. Furthermore, LHPA axis activity has been implicated in the development of sensitization to abused drugs, and F344 rats exhibit greater behavioral sensitization to psychostimulants. Accordingly, we hypothesized that there may be some overlap between the neurobiological mechanisms that underlie these strain differences in LHPA axis activity and in behavioral sensitization to psychostimulants. We examined the effects of acute and repeated methamphetamine (4 mg/kg) treatments on the regulation of hippocampal glucocorticoid receptors (GR mRNA) and mineralocorticoid receptors (MR mRNA) in F344 and LEW rats. Our results showed that acute treatment with methamphetamine (MAP) does not alter the level of expression of GR or MR mRNA in both strains. However, repeated treatments with MAP decreased the expression of hippocampal GR, but not MR mRNA specifically in F344 rats. The same repeated treatments had no effect on either GR or MR mRNA in LEW rats. This selective MAP regulation of the level of expression of hippocampal GR mRNA in F344 suggests that these receptors may play a role in the development of behavioral sensitization to MAP in this strain. The lack of alteration in hippocampal GR mRNA in LEW rats suggests that plasticity of hippocampal GR may not be critical for the development of behavioral sensitization to MAP in this strain.

Effects of treatment with amphetamine and diazepam on Mycobacterium bovis-induced infection in hamsters

Tuberculosis is an example of an infection with an intracellular bacterium in which sensitivity is determined mainly by the host response. Macrophages are the architectural and functional units of the granulomas described in tuberculosis. Treatment with amphetamine (AMPH) and diazepam has been reported to decrease macrophage activity. The present experiment was undertaken to investigate the effects of AMPH and/or diazepam given alone or in combination on hamster resistance to Mycobacterium bovis. The effects of these treatments on serum cortisol levels were also studied. Adult hamsters were treated i.p. with AMPH (group E1 = 1.0 or 2.0 mg/kg/day), with AMPH (group E2 = 1.0 or 2.0 mg/kg/day) plus diazepam (2.0 mg/kg/day), with diazepam (group E3 = 2.0 mg/kg/day), or with control vehicles (1.0 ml/kg/day) for 40 days. Six days after the beginning of the treatments, the animals received identical inoculum concentrations of M. bovis. Hamsters treated with AMPH plus diazepam exhibited: 1) increased weight loss; 2) increased mortality; 3) increased scores of M. bovis colony forming units (CFU) isolated from liver, lung and spleen; 4) increased granuloma areas measured in the liver, lung and spleen. These effects were not induced by AMPH (1.0 or 2.0 mg/kg/day) given alone and were produced by diazepam (2.0 mg/kg/day) treatment per se. Furthermore, AMPH (2.0 mg/kg/day) and diazepam (2.0 mg/kg/day) given alone or in combination for 20 days increased the serum levels of cortisol in relation to control hamsters, with the effect being higher in the animals treated with both drugs. The present data, which demonstrate an impaired defense against M. bovis in hamsters treated with AMPH plus diazepam or with diazepam alone, were tentatively explained on the basis of a direct and/or indirect action of the drugs on macrophage/lymphocyte activity. In the former case, the effects may be related to stimulation of peripheral benzodiazepine receptor sites (PBR) present on macrophages/lymphocytes and/or to a direct effect of ACTH on immune cells, while in the latter they may be mediated by cortisol via PBR and ACTH stimulation of the adrenals.