Chronic unpredictable stress augments +3,4-methylenedioxymethamphetamine-induced monoamine depletions: the role of corticosterone.
Neuroscience April 10, 2009 DOI: 10.1016/j.neuroscience.2009.01.067 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Experimental animal study Peer reviewed |
|---|---|
| Population | Rats |
| Interventions | MDMA Chronic unpredictable stress Metyrapone |
| Dose | MDMA 5 mg/kg every 2 h (four doses); metyrapone 50 mg/kg i.p. |
| Duration | 10 days of stress, MDMA challenge on day 11, rats killed 5 days later |
| Topics | MDMA |
| Key findings | Chronic unpredictable stress enhanced MDMA-induced serotonin depletions in all three brain regions and produced striatal dopamine depletion only in stressed rats; these effects were blocked by the corticosterone synthesis inhibitor metyrapone, suggesting a role for elevated basal corticosterone. |
Abstract
Exposure to stress alters the behavioral and neurochemical effects of drugs of abuse. However, it is unknown if chronic stress can affect the serotonergic depletions induced by the psychostimulant drug 3,4-methylenedioxymethamphetamine (MDMA). Rats were exposed to 10 days of chronic unpredictable stress (CUS) which resulted in the predicted elevation of basal plasma corticosterone concentrations. On the 11th day, rats received four challenge doses of MDMA (5 mg/kg every 2 h, i.p.) or saline. Five days later, rats were killed and serotonin (5-HT) and dopamine content were measured in the striatum, hippocampus, and frontal cortex. MDMA produced greater depletions of 5-HT in all three brain regions of rats pre-exposed to CUS compared to rats not exposed to CUS. CUS-exposed rats also had an augmented acute hyperthermic response but a similar increase in plasma corticosterone after challenge injections of MDMA compared with non-stressed rats similarly challenged with MDMA. Moreover, CUS-exposed rats exhibited an MDMA-induced depletion of striatal dopamine that was absent in non-stressed rats that received MDMA. To investigate the role of corticosterone in these effects, the corticosterone synthesis inhibitor, metyrapone (50 mg/kg i.p.), was administered prior to each stressor on each of the 10 days of CUS. Metyrapone blocked the chronic stress-induced elevation in basal plasma corticosterone, prevented the enhancement of MDMA-induced hyperthermia, and blocked the enhanced depletions of 5-HT and dopamine in CUS-exposed rats, but had no effect on the acute MDMA-induced increases in plasma corticosterone. These findings suggest that CUS alone can increase the basal level of corticosterone that in turn, plays an important role in enhancing the sensitivity of both 5-HT and dopamine terminals to the hyperthermic and monoamine depleting effects of MDMA without altering the acute corticosterone response to an MDMA challenge.