Ca2+ oscillations in response to methamphetamine in dopamine neurons of the ventral tegmental area in rats subchronically treated with this drug

Methamphetamine causes mitrochondrial oxidative damage in human T lymphocytes leading to functional impairment

Methamphetamine (METH) abuse is known to be associated with an inordinate rate of infections. Although many studies have described the association of METH exposure and immunosuppression, so far the underlying mechanism still remains elusive. In this study, we present evidence that METH exposure resulted in mitochondrial oxidative damage and caused dysfunction of primary human T cells. METH treatment of T lymphocytes led to a rise in intracellular calcium levels that enhanced the generation of reactive oxygen species. TCR-CD28 linked calcium mobilization and subsequent uptake by mitochondria in METH-treated T cells correlated with an increase in mitochondrion-derived superoxide. Exposure to METH-induced mitochondrial dysfunction in the form of marked decrease in mitochondrial membrane potential, increased mitochondrial mass, enhanced protein nitrosylation and diminished protein levels of complexes I, III, and IV of the electron transport chain. These changes paralleled reduced IL-2 secretion and T cell proliferative responses after TCR-CD28 stimulation indicating impaired T cell function. Furthermore, antioxidants attenuated METH-induced mitochondrial damage by preserving the protein levels of mitochondrial complexes I, III, and IV. Altogether, our data indicate that METH can cause T cell dysfunction via induction of oxidative stress and mitochondrial injury as underlying mechanism of immune impairment secondary to METH abuse.

Neuronal dysfunction of a long projecting multisynaptic pathway in response to methamphetamine using manganese-enhanced MRI

RATIONALE

Manganese (Mn2+)-enhanced magnetic resonance imaging (MEMRI) is an emerging in vivo MR approach for pharmacological research. One new application of MEMRI in this area is to characterize functional changes of a specific neural circuit that is essential to the central effects of a drug challenge.

OBJECTIVES

To develop and validate such use of MEMRI in neuropharmacology, the current study applied MEMRI to visualize functional changes within a multisynaptic pathway originating from fasciculus retroflexus (FR) that is central to a commonly abused psychostimulant, methamphetamine (MA).

METHODS

Twelve rats were injected intraperitoneally with MA (10 mg/kg) or saline every 2 h for a total of four injections. After 6 days, Mn2+ was injected into the habenular nucleus (FR origin) of all animals, and MEMRI was repeatedly performed at certain points in time over 48 h. The evolution of Mn2+-induced signal enhancement was assessed across the FR tract, the ventral tegmental area (VTA), the striatum, the nucleus accumbens, and the prefrontal cortex (PFC), in both MA-injected animals and controls.

RESULTS

MA treatment was found to affect the complexity and efficiency of Mn2+ uptake in the VTA, via the FR tract, with significantly increased Mn2+ accumulation in the VTA, the dorsomedial part of the striatum, and the PFC.

CONCLUSIONS

MEMRI successfully visualizes disruptions in the multisynaptic pathway as the consequences of repeated MA exposure. MEMRI is potentially an important method in the future to investigate functional changes within a specific pathway under the influences of pharmacological agents, given its excellent functional, in vivo, spatial, and temporal properties.

Structural and functional cellular alterations underlying the toxicity of methamphetamine in rat retina and prefrontal cortex

The consumption of illicit drugs is an increasing problem in contemporary societies, and is one of the major causes of death and illness all over the world. Methamphetamine is among the drugs more widely used. Although evidence for a role of reactive species--especially reactive oxygen species (ROS) and apoptotic events--has been shown, the mechanism(s) underlying the cellular toxicity induced by this drug is not yet fully identified. In this context the elucidation of the cytotoxic effects induced by methamphetamine in rat frontal cortex and retina, which compromise cell viability and ultimately result in cell death, can further contribute to the understanding of its mechanism of action. This knowledge may provide new insights into the development of new therapeutic approaches to prevent or ameliorate deleterious alterations of the nervous system. The use of epifluorescence microscopy associated with different fluorescent probes, markers of structural and/or functional cell parameters, can be used as a powerful tool to carry out those studies, in particular, the viability probes propidium iodide (PI) to assess plasma membrane integrity and fluorescein diacetate (FDA), which can monitor intracellular esterase activity and/or pH. In a preliminary study, the kinetic assessment of cellular changes induced by different drug concentrations (0, 1.2, 3, and 6 mM) allowed detection of dose-dependent alterations that are observed earlier in the retina. In fact, in the retina it was possible to monitor alterations (at 4 h of incubation) both in plasma membrane integrity and in esterase activity and/or pH for the lowest drug concentration (1.2 mM). In the prefrontal cortex these changes were only visible for drug concentrations > or = 3 mM. This work is a novel approach to the mechanisms of action of illicit drugs in the central nervous system and will provide the foundations and guidelines for further investigations in the context of tolerance, dependence, and addiction.