MDMA‐evoked changes in [11C]raclopride and [11C]NMSP binding in living pig brain

MDMA (Ecstasy) reduces the binding of two different radioligands to dopamine D2-like receptors in the striatum of living pigs, as measured by PET. The binding potential of [11C]raclopride fell by 35% at 45 minutes and 22% at 165 minutes after MDMA infusion, similar to changes caused by d-amphetamine. Unexpectedly, the binding of [11C]NMSP also decreased, by 30% in the first scan and 50% in the second, unlike its typical insensitivity to dopamine release. The simultaneous release of dopamine and serotonin by MDMA may explain the progressive decline in NMSP binding.

Study at a glance

Abstract

Abstract Positron emission tomography (PET) studies with radiolabeled dopamine D 2 ‐like receptor ligands reveal d ‐amphetamine‐evoked increases in the competition from endogenous dopamine. However, the corresponding effects of methylenedioxymethamphetamine (MDMA, “Ecstasy”), which releases catecholamines and also serotonin, are unknown. Using PET, we measured the binding potentials ( pB s) of the benzamide [ 11 C]raclopride and the butyrophenone N‐[ 11 C]methylspiperone ([ 11 C]NMSP) in brain of living pigs first in a baseline condition and at 45 and 165 min after infusion of (+/‐)‐MDMA‐HCl (1 mg/kg, i.v.). Concomitant studies of cerebral blood flow did not reveal significant perfusion changes in the cerebellum reference region or in striatum, supporting the present use of reference tissue methods for the mapping of MDMA‐evoked pB changes. Relative to the baseline pB of [ 11 C]raclopride for dopamine D 2/3 receptors in striatum ( pB = 1.5–2.2), MDMA‐treatment reduced pB by 35% in the first posttreatment scan and by 22% in the second posttreatment scan, comparable to changes typically evoked by d ‐amphetamine at a similar dose. In most previous studies, the in vivo binding of butyrophenones has been nearly insensitive to d ‐amphetamine‐evoked dopamine release. However, we found the baseline pB of [ 11 C]NMSP for dopamine D 2 ‐like receptors in striatum ( pB = 4–5) was decreased by 30% in the first post‐MDMA scan and by 50% in the second post‐MDMA scan, irrespective of assumptions about the extent of equilibrium binding attained during the 90‐min‐long PET recordings. Distinct properties of MDMA such as simultaneous release of dopamine and serotonin in brain may account for the present finding of progressive decline in the availability of [ 11 C]NMSP binding sites in striatum. Synapse 53:222–233, 2004. © 2004 Wiley‐Liss, Inc.