Driving under
methylenedioxymethamphetamine (
MDMA) influence increases the risk of being involved in a car accident, which in turn can lead to
traumatic brain injury. The behavioral deficits after
traumatic brain injury (TBI) are closely connected to
dopamine pathway dysregulation. We have previously demonstrated in mice that low
MDMA doses prior to mTBI can lead to better performances in cognitive tests. The purpose of this study was to assess in mice the changes in the
dopamine system that occurs after both
MDMA and minimal
traumatic brain injury (mTBI). Experimental mTBI was induced using a concussive
head trauma device. One hour before injury, animals were subjected to
MDMA. Administration of
MDMA before injury normalized the alterations in
tyrosine hydroxylase (TH) levels that were observed in mTBI mice. This normalization was also able to lower the elevated
dopamine receptor type 2 (D2) levels observed after mTBI.
Brain-derived neurotrophic factor (
BDNF) levels did not change following injury alone, but in mice subjected to
MDMA and mTBI, significant elevations were observed. In the behavioral tests,
haloperidol reversed the neuroprotection seen when
MDMA was administered prior to injury. Altered
catecholamine synthesis and high D2 receptor levels contribute to
cognitive dysfunction, and strategies to normalize TH signaling and D2 levels may provide relief for the deficits observed after injury. Pretreatment with
MDMA kept TH and D2 receptor at normal levels, allowing regular
dopamine system activity. While the beneficial effect we observe was due to a dangerous
recreational drug, understanding the alterations in
dopamine and the mechanism of dysfunction at a cellular level can lead to legal
therapies and potential candidates for clinical use.