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Methylenedioxymethamphetamine induces spontaneous tail-flicks in the rat via 5-HT1A receptors
1Neurobiology Division, Fondax-Groupe de Recherche Servier, Puteaux, France.
Abstract:
In rats lightly restrained in horizontal cylinders, (+/-)-3,4-methylenedioxymethamphetamine (MDMA) dose dependently (0.16-10.0 mg/kg, s.c.) elicited spontaneous tail-flicks; that is, tail-flicks in the absence of extraneous stimulation. In contrast, amphetamine over a similar dose-range was inactive. Selective inhibitors of 5-hydroxytryptamine (5-HT) uptake and carrier-mediated 5-HT release, paroxetine and citalopram, did not induce spontaneous tail-flicks themselves and blocked those induced by MDMA. In distinction, maprotiline and bupropion, selective inhibitors of noradrenaline and dopamine uptake, respectively, failed to modify the action of MDMA. Spontaneous tail-flicks elicited by MDMA were unaffected by the selective 5-HT3 receptor antagonists, ICS 205,930 and GR 38032F. They were attenuated by the mixed 5-HT1/5-HT2 receptor antagonist, methiotepin, the mixed 5-HT1A/5-HT1B receptor antagonist, (-)-alprenolol and the mixed 5-HT1A/5-HT2 receptor antagonist, spiperone, but not by the selective 5-HT1C/5-HT2 receptor antagonists, ritanserin, ICI 169,369 and ketanserin. The novel 5-HT1A receptor antagonists, BMY 7378 and NAN-190, each abolished MDMA-evoked spontaneous tail-flicks. Selective D1, D2, alpha 1, alpha 2, beta 1 and beta 2 antagonists had little influence upon induction of spontaneous tail-flicks by MDMA. These data indicate that MDMA evokes spontaneous tail-flicks in the rat via a release of 5-HT which acts at 5-HT1A receptors. Thus, 5-HT1A receptors appear to be involved in the acute functional actions of MDMA.
Insights
MDMA (3,4-methylenedioxymethamphetamine) causes spontaneous tail-flicks in rats by releasing serotonin (5-HT). This action is mediated through 5-HT1A receptors, highlighting their role in MDMA
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- MDMA (3,4-methylenedioxymethamphetamine) is a psychoactive drug with complex neurochemical effects.
- Spontaneous tail-flicks in rats are a behavioral response indicative of central nervous system activity.
- The precise mechanisms underlying MDMA-induced behaviors, particularly those involving serotonin (5-HT) pathways, require further elucidation.
Purpose of the Study:
- To investigate the neurochemical mechanisms by which MDMA elicits spontaneous tail-flicks in rats.
- To determine the specific serotonin receptor subtypes involved in mediating this MDMA-induced behavior.
- To differentiate the role of serotonin pathways from other neurotransmitter systems, such as dopamine and noradrenaline, in this response.
Main Methods:
- Administration of varying doses of MDMA to rats and observation of spontaneous tail-flick responses.
- Utilizing selective serotonin reuptake inhibitors (SSRIs) and serotonin releasers (paroxetine, citalopram) to assess their impact on MDMA-induced tail-flicks.
- Employing a range of selective and non-selective receptor antagonists targeting various serotonin (5-HT3, 5-HT1A, 5-HT1B, 5-HT1C, 5-HT2) and other neurotransmitter receptors (dopamine, adrenergic) to probe the underlying pharmacology.
Main Results:
- MDMA dose-dependently induced spontaneous tail-flicks, while amphetamine did not.
- Selective serotonin uptake inhibitors and releasers blocked MDMA-induced tail-flicks, whereas dopamine and noradrenaline uptake inhibitors did not affect this response.
- MDMA-evoked tail-flicks were specifically antagonized by 5-HT1A receptor antagonists, indicating a critical role for this receptor subtype.
Conclusions:
- MDMA-induced spontaneous tail-flicks in rats are primarily mediated by the release of serotonin (5-HT).
- The 5-HT1A receptor subtype is crucially involved in mediating the acute functional effects of MDMA observed in this behavioral model.
- These findings elucidate a specific serotonergic pathway contributing to the behavioral pharmacology of MDMA.