Abstract
We showed that the serotonin (5-HT) neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) reduces brain tissue 5-HT, decreases expression of 5-HT transporter (SERT) protein, and increases expression of glial fibrillary acidic protein (GFAP). In contrast, doses of (±)-3,4-methylenedioxymethamphetamine (MDMA) that decrease brain tissue 5-HT fail to alter expression of SERT or GFAP. Using a new and highly sensitive anti-SERT antibody, we determined whether MDMA alters the subcellular distribution of SERT protein by measuring SERT expression in endosomes and plasma membranes 2 weeks after MDMA administration. Rat brain tissues (caudate, cortex, and hippocampus) were collected 3 days and 2 weeks after MDMA (7.5 mg/kg i.p., every 2 h × 3 doses) or 5,7-DHT (150 μg/rat i.c.v.) administration. Representative results from cortex are as follows. At both 3 days and 2 weeks postinjection, MDMA decreased tissue 5-HT (65%) and had no effect on GFAP expression. MDMA increased heat shock protein 32 (HSP32; a marker for microglial activation) expression (30%) at 3 days, but not 2 weeks. MDMA did not alter SERT expression at either time point and did not alter SERT levels in either endosomes or plasma membranes (2 weeks). 5,7-DHT decreased tissue 5-HT (80%), increased HSP32 expression at both time points (about 50%), and increased GFAP expression at 2 weeks (40%). 5,7-DHT decreased SERT expression (33%) at 2 weeks, but not at 3 days. These findings indicate that a dosing regimen of MDMA that depletes brain 5-HT does not alter SERT protein expression or the distribution of SERT between endosomes and the plasma membrane and does not produce detectable evidence for neurotoxicity.
Footnotes
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doi:10.1124/jpet.105.088476.
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ABBREVIATIONS: MDMA, (±)-3,4-methylenedioxymethamphetamine; 5-HT, serotonin; SERT, 5-HT transporter; GFAP, glial fibrillary acidic protein; DA, dopamine; METH, methamphetamine; 5,7-DHT, 5,7-dihydroxytryptamine; [125I]RTI-55, 3β-(4′-125iodophenyl)tropan-2β-carboxylic acid methyl ester; HSP32, heat shock protein 32; TBS, Tris-buffered saline; PBR, peripheral benzodiazepine receptor; PK-11195, 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carboxamide.
- Received April 25, 2005.
- Accepted June 1, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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