Abstract
3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is known to produce euphoric states, but may also cause adverse consequences in humans, such as hyperthermia and neurocognitive deficits. Although MDMA consumption has been associated with visual problems, the effects of this recreational drug in retinal physiology have not been addressed hitherto. In this work, we evaluated the effect of a single MDMA administration in the rat electroretinogram (ERG). Wistar rats were administered MDMA (15 mg/kg) or saline and ERGs were recorded before (Baseline ERG), and 3 h, 24 h, and 7 days after treatment. A high temperature (HT) saline-treated control group was also included. Overall, significantly augmented and shorter latency ERG responses were found in MDMA and HT groups 3 h after treatment when compared to Baseline. Twenty-four hours after treatment some of the alterations found at 3 h, mainly characterized by shorter latency, tended to return to Baseline values. However, MDMA-treated animals still presented increased scotopic a-wave and b-wave amplitudes compared to Baseline ERGs, which were independent of temperature elevation though the latter might underlie the acute ERG alterations observed 3 h after MDMA administration. Seven days after MDMA administration recovery from these effects had occurred. The effects seem to stem from specific changes observed at the a-wave level, which indicates that MDMA affects subacutely (at 24 h) retinal physiology at the outer retinal (photoreceptor/bipolar) layers. In conclusion, we have found direct evidence that MDMA causes subacute enhancement of the outer retinal responses (most prominent in the a-wave), though ERG alterations resume within one week. These changes in photoreceptor/bipolar cell physiology may have implications for the understanding of the subacute visual manifestations induced by MDMA in humans.
Highlights
Since MDMA induces an acute increase in body temperature, light responses are increased and accelerated
One week after MDMA administration the ERG alterations observed at 24 h were no longer present
In photopic responses, contrarily to the effect found at 24 h, no increased bwave amplitude during light adaptation was observed 7 days after MDMA administration when compared to Baseline
Summary
3,4-methylenedioxymethamphetamine (MDMA; ecstasy) is a recreational drug often consumed at ‘‘rave’’ parties. The death rate caused by ecstasy in humans is relatively low compared to other drugs of abuse, it has been associated with potential fatal consequences, including hyperthermia, rhabdomyolysis, hepatotoxicity, cardiotoxicity, and acute renal failure [3,4,5] It has been associated with significant deficits in neurocognitive function, mainly verbal memory [1,6]. The acute release can be followed by long-term neurotoxic transmitter depletion, mainly 5-HT, in some brain regions, as experimentally observed in the rat [10,11] and monkey [12] It is not yet clear whether these MDMA neurotoxic effects underlie overt cognitive deficits. Taking the scarcity of direct physiological studies into account, we evaluated potential alterations in the rat retinal light responses induced by a single peripheral administration of MDMA. These findings suggest a direct retinal effect of MDMA that may have implications for the understanding of visual perceptual effects induced by this drug
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