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M. Kirkpatrick

Urinary and plasma oxytocin changes in response to MDMA or intranasal oxytocin administration

August 16, 2016 / MDMA, Neuroscience, Papers, Publications / By / , , ,

Abstract

BACKGROUND:
The neuropeptide oxytocin (OT) has received increased experimental attention for its putative role in both normal social functioning and several psychiatric disorders that are partially characterized by social dysfunction (e.g., autism spectrum disorders: ASD). Many human experimental studies measure circulating plasma levels of OT in order to examine the relationship between the hormone and behavior. Urinary OT (uOT) assays offer a simple, easy, and non-invasive method to measure peripheral hormone levels, but the correspondence between uOT and plasma OT (pOT) levels is unclear. Here, we conducted two within-subjects, double-blind studies exploring changes in uOT and pOT levels following administration of two drugs: MDMA, an oxytocin-releasing drug (Study 1), and intranasal oxytocin (INOT: Study 1 and 2).
METHODS:
In Study 1, 14 adult participants (2 females) were each administered either oral 1.5mg/kg MDMA or 40IU INOT across two different study sessions. In Study 2, 10 male participants (adolescents and young adults) diagnosed with ASD received either 40IU INOT or placebo across two different sessions. In both studies, blood and urine samples were collected before and after drug administration at each study session. For Study 1, 10 participants provided valid plasma and urine samples for the MDMA session, and 8 provided valid samples for the INOT session. For Study 2, all 10 participants provided valid samples for both INOT and placebo sessions. Pre- and post-administration levels of pOT and uOT were compared. Additionally, correlations between percent change from baseline uOT and pOT levels were examined.
RESULTS:
Study 1: Plasma OT and uOT levels significantly increased after administration of MDMA and INOT. Furthermore, uOT levels were positively correlated with pOT levels following administration of MDMA (r=0.57, p=0.042) but not INOT (r=0.51, p=0.097). Study 2: There was a significant increase in uOT levels after administration of INOT, but not after administration of placebo. Under both conditions, INOT and placebo, significant increases in pOT levels were not observed. Additionally, change from baseline uOT and pOT levels were positively correlated (r=0.57, p=0.021). There was no significant correlation between uOT and pOT levels following placebo administration.
CONCLUSION:
Our results show a measurable and significant increase in pOT and uOT levels after the administration of MDMA (Study 1) and INOT (Study 1 and Study 2). Additionally, a positive correlation between uOT and pOT levels was observed in both samples (healthy adults and ASD patients) in at least one condition. However, uOT and pOT levels were not correlated under all conditions, suggesting that uOT levels do not fully correspond to pOT levels in the time windows we measured. Future studies should further examine the relationship between levels of pOT and uOT in healthy and clinical populations on measures of social behavior because uOT may serve as an additional non-invasive method to measure peripheral OT changes.
Francis, S. M., Kirkpatrick, M. G., de Wit, H., & Jacob, S. (2016). Urinary and plasma oxytocin changes in response to MDMA or intranasal oxytocin administration. Psychoneuroendocrinology, 74, 92-100. 10.1016/j.psyneuen.2016.08.011
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Oxytocin receptor gene variation predicts subjective responses to MDMA

January 20, 2016 / MDMA, Neuroscience, Papers, Psychology, Publications / By / , , , , ,

Abstract

3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”) enhances desire to socialize and feelings of empathy, which are thought to be related to increased oxytocin levels. Thus, variation in the oxytocin receptor gene (OXTR) may influence responses to the drug. Here we examined the influence of a single OXTR nucleotide polymorphism (SNP) on responses to MDMA in humans. Based on findings that carriers of the A allele at rs53576 exhibit reduced sensitivity to oxytocin-induced social behavior, we hypothesized that these individuals would show reduced subjective responses to MDMA, including sociability. In this 3-session, double blind, within-subjects study, healthy volunteers with past MDMA experience (N = 68) received a MDMA (0, 0.75 mg/kg and 1.5 mg/kg) and provided self-report ratings of sociability, anxiety, and drug effects. These responses were examined in relation to rs53576. MDMA (1.5 mg/kg) did not increase sociability in individuals with the A/A genotype as it did in G allele carriers. The genotypic groups did not differ in responses at the lower MDMA dose, or in cardiovascular or other subjective responses. These findings are consistent with the idea that MDMA-induced sociability is mediated by oxytocin, and that variation in the oxytocin receptor gene may influence responses to the drug.

Bershad, A. K., Weafer, J. J., Kirkpatrick, M. G., Wardle, M. C., Miller, M. A., & de Wit, H. (2016). Oxytocin receptor gene variation predicts subjective responses to MDMA. Social neuroscience. http://dx.doi.org/10.1080/17470919.2016.1143026

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Intimate insight: MDMA changes how people talk about significant others

April 28, 2015 / MDMA, Papers, Psychology, Publications / By / , , ,

Abstract

Rationale: ±3,4-methylenedioxymethamphetamine (MDMA) is widely believed to increase sociability. The drug alters speech production and fluency, and may influence speech content. Here, we investigated the effect of MDMA on speech content, which may reveal how this drug affects social interactions.

Method: Thirty-five healthy volunteers with prior MDMA experience completed this two-session, within-subjects, double-blind study during which they received 1.5 mg/kg oral MDMA and placebo. Participants completed a five-minute standardized talking task during which they discussed a close personal relationship (e.g. a friend or family member) with a research assistant. The conversations were analyzed for selected content categories (e.g. words pertaining to affect, social interaction, and cognition), using both a standard dictionary method (Pennebaker’s Linguistic Inquiry and Word Count: LIWC) and a machine learning method using random forest classifiers.

Results: Both analytic methods revealed that MDMA altered speech content relative to placebo. Using LIWC scores, the drug increased use of social and sexual words, consistent with reports that MDMA increases willingness to disclose. Using the machine learning algorithm, we found that MDMA increased use of social words and words relating to both positive and negative emotions.

Conclusions: These findings are consistent with reports that MDMA acutely alters speech content, specifically increasing emotional and social content during a brief semistructured dyadic interaction. Studying effects of psychoactive drugs on speech content may offer new insights into drug effects on mental states, and on emotional and psychosocial interaction.

Baggott, M. J., Kirkpatrick, M. G., Bedi, G., & de Wit, H. (2015). Intimate insight: MDMA changes how people talk about significant others. Journal of Psychopharmacology, 0269881115581962. https://dx.doi.org/10.1177/0269881115581962
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Prosocial effects of MDMA: A measure of generosity

March 3, 2015 / MDMA, Papers, Psychology, Publications / By / , , ,

Abstract

Background: 3,4-methylenedioxymethamphetamine (MDMA) produces “prosocial” effects that contribute to its recreational use. Few studies have examined the cognitive and behavioral mechanisms by which MDMA produces these effects. Here we examined the effect of MDMA on a specific prosocial effect, i.e. generosity, using a task in which participants make decisions about whether they or another person will receive money (Welfare Trade-Off Task; WTT).

Methods: The project included one study without drug administration and one with MDMA. In Study 1, we administered the WTT to healthy adults (N = 361) and examined their performance in relation to measures of personality and socioeconomic status. In Study 2, healthy volunteers with MDMA experience (N = 32) completed the WTT after MDMA administration (0, 0.5, or 1.0 mg/kg).

Results: As expected, in both studies participants were more generous with a close friend than an acquaintance or stranger. In Study 1, WTT generosity was related to household income and trait Agreeableness. In Study 2, MDMA (1.0 mg/kg) increased generosity toward a friend but not a stranger, whereas MDMA (0.5 mg/kg) slightly increased generosity toward a stranger, especially among female participants.

Conclusions: These data indicate that the WTT is a valuable, novel tool to assess a component of prosocial behavior, i.e. generosity to others. The findings support growing evidence that MDMA produces prosocial effects, but, as with oxytocin, these appear to depend on the social proximity of the relationships. The brain mechanisms underlying the construct of generosity, or the effects of MDMA on this measure, remain to be determined.

Kirkpatrick, M., Delton, A. W., de Wit, H., & Robertson, T. E. (2015). Prosocial effects of MDMA: A measure of generosity. Journal of Psychopharmacology. https://dx.doi.org/10.1177/0269881115573806
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