Pharmacodynamic characterization of insulin on MDMA-induced thermogenesis

Increased kynurenine concentration attenuates serotonergic neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in rats through activation of aryl hydrocarbon receptor

3,4-Methylenedioxymethamphetamine (MDMA) is an amphetamine derivative that has been shown to produce serotonergic damage in the brains of primates, including humans, and of rats. Tryptophan, the precursor of serotonin, is primarily degraded through the kynurenine (KYN) pathway, producing among others KYN, the main metabolite of this route. KYN has been reported as an endogenous agonist of the aryl hydrocarbon receptor (AhR), a transcription factor involved in several neurological functions. This study aims to determine the effect of MDMA on the KYN pathway and on AhR activity and to establish their role in the long-term serotonergic neurotoxicity induced by the drug in rats. Our results show that MDMA induces the activation of the KYN pathway, mediated by hepatic tryptophan 2,3-dioxygenase (TDO). MDMA also activated AhR as evidenced by increased AhR nuclear translocation and CYP1B1 mRNA expression. Autoradiographic quantification of serotonin transporters showed that both the TDO inhibitor 680C91 and the AhR antagonist CH-223191 potentiated the neurotoxicity induced by MDMA, while administration of exogenous l-kynurenine or of the AhR positive modulator 3,3'-diindolylmethane (DIM) partially prevented the serotonergic damage induced by the drug. The results demonstrate for the first time that MDMA increases KYN levels and AhR activity, and these changes appear to play a role in limiting the neurotoxicity induced by the drug. This work provides a better understanding of the physiological mechanisms that attenuate the brain damage induced by MDMA and identify modulation of the KYN pathway and of AhR as potential therapeutic strategies to limit the negative effects of MDMA.

Potentiation of Ecstasy-induced hyperthermia and FAT/CD36 expression in chronically exercised animals

Fatal hyperthermia as a result of 3,4-methylenedioxymethamphetamine (MDMA) use involves non-esterified free fatty acids (NEFA) and the activation of mitochondrial uncoupling proteins (UCP). NEFA gain access into skeletal muscle via specific transport proteins, including fatty acid translocase (FAT/CD36). FAT/CD36 expression is known to increase following chronic exercise. Previous studies have demonstrated the essential role of NEFA and UCP3 in MDMA-induced hyperthermia. The aims of the present study were to use a chronic exercise model (swimming for two consecutive hours per day, five days per wk for six wk) to increase FAT/CD36 expression in order to: 1) determine the contribution of FAT/CD36 in MDMA (20 mg/kg, s.c.)-mediated hyperthermia; and 2) examine the effects of the FAT/CD36 inhibitor, SSO (sulfo-N-succinimidyl oleate), on MDMA-induced hyperthermia in chronic exercise and sedentary control rats. MDMA administration resulted in hyperthermia in both sedentary and chronic exercise animals. However, MDMA-induced hyperthermia was significantly potentiated in the chronic exercise animals compared to sedentary animals. Additionally, chronic exercise significantly reduced body weight, increased FAT/CD36 protein expression levels and reduced plasma NEFA levels. The FAT/CD36 inhibitor, SSO (40 mg/kg, ip), significantly attenuated the hyperthermia mediated by MDMA in chronic exercised but not sedentary animals. Plasma NEFA levels were elevated in sedentary and exercised animals treated with SSO prior to MDMA suggesting attenuation of NEFA uptake into skeletal muscle. Chronic exercise did not alter skeletal muscle UCP3 protein expression levels. In conclusion, chronic exercise potentiates MDMA-mediated hyperthermia in a FAT/CD36 dependent fashion.

Synthetic cathinones ("bath salts")

BACKGROUND

Synthetic cathinones are popularly referred to in the media as "bath salts." Through the direct and indirect activation of the sympathetic nervous system, smoking, snorting, or injecting synthetic cathinones can result in tachycardia, hypertension, hyperthermia, myocardial infarction, and death.

OBJECTIVE

The chemical structures and names of bath salts identified by the Ohio Attorney General's Bureau of Criminal Investigation are presented. Based on their common pharmacophores, we review the history, pharmacology, toxicology, detection methods, and clinical implications of synthetic cathinones. Through the integration of this information, the pharmacological basis for the management of patients using synthetic cathinones is presented.

DISCUSSION

Synthetic cathinones activate central serotonergic and dopaminergic systems contributing to acute psychosis and the peripheral activation of the sympathetic nervous system. The overstimulation of the sympathetic nervous system contributes to the many toxicities reported with bath salt use. The pharmacological basis for managing these patients is targeted at attenuating the activation of these systems.

CONCLUSIONS

Treatment of patients presenting after using bath salts should be focused on reducing agitation and psychosis and supporting renal perfusion. The majority of successfully treated synthetic cathinones cases have used benzodiazepines and antipsychotics along with general supportive care.

Loss of histaminergic modulation of thermoregulation and energy homeostasis in obese mice

Histamine acts centrally to increase energy expenditure and reduce body weight by mechanisms not fully understood. It has been suggested that in the obese state hypothalamic histamine signaling is altered. Previous studies have also shown that histamine acting in the preoptic area controls thermoregulation. We aimed to study the influence of preoptic histamine on body temperature and energy homeostasis in control and obese mice. Activating histamine receptors in the preoptic area by increasing the concentration of endogenous histamine or by local injection of specific agonists induced an elevation of core body temperature and decreased respiratory exchange ratio (RER). In addition, the food intake was significantly decreased. The hyperthermic effect was associated with a rapid increase in mRNA expression of uncoupling proteins in thermogenic tissues, the most pronounced being that of uncoupling protein (UCP) 1 in brown adipose tissue and of UCP2 in white adipose tissue. In diet-induced obese mice histamine had much diminished hyperthermic effects as well as reduced effect on RER. Similarly, the ability of preoptic histamine signaling to increase the expression of uncoupling proteins was abolished. We also found that the expression of mRNA encoding the H1 receptor subtype in the preoptic area was significantly lower in obese animals. These results indicate that histamine signaling in the preoptic area modulates energy homeostasis by regulating body temperature, metabolic parameters and food intake and that the obese state is associated with a decrease in neurotransmitter's influence.

Role of serotonin and/or norepinephrine in the MDMA-induced increase in extracellular glucose and glycogenolysis in the rat brain

The acute administration of MDMA has been shown to promote glycogenolysis and increase the extracellular concentration of glucose in the striatum. In the present study the role of serotonergic and/or noradrenergic mechanisms in the MDMA-induced increase in extracellular glucose and glycogenolysis was assessed. The relationship of these responses to the hyperthermia produced by MDMA also was examined. The administration of MDMA (10mg/kg, i.p.) resulted in a significant and sustained increase of 65-100% in the extracellular concentration of glucose in the striatum, as well as in the prefrontal cortex and hippocampus, and a 35% decrease in brain glycogen content. Peripheral blood glucose was modestly increased by 32% after MDMA treatment. Treatment of rats with fluoxetine (10mg/kg, i.p.) significantly attenuated the MDMA-induced increase in extracellular glucose in the striatum but had no effect on MDMA-induced glycogenolysis or hyperthermia. Treatment with prazosin (1mg/kg, i.p.) did not alter the glucose or glycogen responses to MDMA but completely suppressed MDMA-induced hyperthermia. Finally, propranolol (3mg/kg, i.p.) significantly attenuated the MDMA-induced increase in extracellular glucose and glycogenolysis but did not alter MDMA-induced hyperthermia. The present results suggest that MDMA increases extracellular glucose in multiple brain regions, and that this response involves both serotonergic and noradrenergic mechanisms. Furthermore, beta-adrenergic and alpha-adrenergic receptors appear to contribute to MDMA-induced glycogenolysis and hyperthermia, respectively. Finally, hyperthermia, glycogenolysis and elevated extracellular glucose appear to be independent, unrelated responses to acute MDMA administration.