MDMA (ecstasy) effects on cultured serotonergic neurons: evidence for Ca2(+)-dependent toxicity linked to release.
Animal studies have established a correlation between release of 5-hydroxytryptamine (5-HT) and the long-term reduction of 5-HT (toxicity) by 3,4-methylenedioxymethamphetamine (MDMA) with the S(+) enantiomer being more active than the R(-). Using a microculture system of fetal raphe neurons, the enantiomers of MDMA were tested to determine if a similar difference in potency existed. The results showed that the development of the uptake capacity of [3H]5-HT in 4-day cultures was half-maximally inhibited by a single application at time of plating of 5 X 10(-6) M S(+)-MDMA and 5 X 10(-5) M R(-)-MDMA. In order to determine if the Ca2(+)-independent release (chemically induced through the transporter protein and inhibited by reuptake blockers) or the Ca2(+)-dependent release (K(+)-induced and inhibited by presynaptic receptors) contributed to the toxicity, fluoxetine and D1 and alpha 2 agonists were studied. The results showed that both forms of release were involved in the loss of [3H]5-HT uptake capacity, with the direct MDMA-induced Ca2(+)-independent (fluoxetine-sensitive) release being the first step. Evidence from binding studies indicates that MDMA has a micromolar affinity for the 5-HT2 receptor, and our studies in culture showed that ketanserin, a specific 5-HT2 antagonist, was effective at attenuating the effects of S(+)-MDMA on the development of the [3H]5-HT uptake capacity by the cultured raphe neurons. The 5-HT2 receptor is linked to increased intracellular Ca2+ through a second messenger phosphatidylinositol (PI)-hydrolysis mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)
Azmitia
E C
EC
Department of Biology, New York University, NY 10003.
Murphy
R B
RB
Whitaker-Azmitia
P M
PM
D015104:3,4-Methylenedioxyamphetamine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000662:Amphetamines / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005473:Fluoxetine / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D011903:Raphe Nuclei / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012701:Serotonin / Q000378:metabolism*
D000662:Amphetamines; D005473:Fluoxetine; D012701:Serotonin; D015104:3,4-Methylenedioxyamphetamine; D007650:Ketanserin; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D002118:Calcium