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U. Schneider

Effects of different subanesthetic doses of (S)-ketamine on neuropsychology, psychopathology, and state of consciousness in man

May 12, 2005 / Ketamine, Papers, Psychology, Publications / By / , , , ,

Abstract

This is the first neuropsychological study using the S-enantiomer of the noncompetetive N-methyl-D-aspartate antagonist ketamine. In 2 randomized placebo-controlled trials we studied effects of two different doses of (S)-ketamine (low dose/high dose) on neuropsychological functions and psychopathology in 12 healthy male volunteers. Impairment was measured via standardized neuropsychological tests. Results indicate that both subanaesthetic doses produce only nonsignificant impair ment in most of the tasks. Tasks involving divided and sustained attention as well as scores for objective and subjective psychopathology show significant impairment in a dose-dependent manner. Implications of these findings for the neuropsychology of attention and schizophrenia are discussed.

Passie, T., Karst, M., Wiese, B., Emrich, H. M., & Schneider, U. (2005). Effects of different subanesthetic doses of (S)-ketamine on neuropsychology, psychopathology, and state of consciousness in man. Neuropsychobiology, 51(4), 226-233. http://dx.doi.org/10.1159%2F000085724
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Ecstasy (MDMA) mimics the post-orgasmic state: impairment of sexual drive and function during acute MDMA-effects may be due to increased prolactin secretion

November 9, 2004 / MDMA, Neuroscience, Papers, Publications / By / , , , ,

Summary

Methylenedioxymethamphetamine (MDMA or ‘‘Ecstasy’’) is a major stimulant drug of abuse worldwide. MDMA produces euphoria, enhances interpersonal communication and feelings of closeness with others. In contrast to the induced emotions of affection and sensual enhancement, clinical studies show that it impairs sexual drive and functioning. In drug-free humans, sexual stimulation with orgasm induces a pronounced secretion of prolactin, which may mediate the post-orgasmic state. The phenomenological features of the psychological state induced by MDMA show some similarities with features of the post-orgasmic state. In addition, MDMA also induces a prominent increase of prolactin plasma levels with a similar time kinetic compared to the post-orgasmic prolactin increase. Here, we present the hypothesis that the impairment of sexual parameters after MDMA may be mediated by increased prolactin.

 

Passie, T., Hartmann, U., Schneider, U., Emrich, H. M., & Krüger, T. H. (2005). Ecstasy (MDMA) mimics the post-orgasmic state: impairment of sexual drive and function during acute MDMA-effects may be due to increased prolactin secretion. Medical hypotheses, 64(5), 899-903. https://dx.doi.org/10.1016/j.mehy.2004.11.044

 

Effects of different subanaesthetic doses of (S)-ketamine on psychopathology and binocular depth inversion in man

January 1, 2003 / Ketamine, Papers, Psychology, Psychotic Disorders, Publications / By / , , , , ,

Abstract

The role of the N-methyl-D-aspartate (NMDA) neurotransmitter system in relation to psychoses is not completely understood, but represent a challenge in neurobiological research. The psychotic states induced by NMDA antagonists such as phencyclidine and ketamine have been described as being most similar to schizophrenia and the NMDA system has been implicated in the pathogenesis of schizophrenia. Binocular depth inversion, an illusion of visual perception, has been shown to be impaired in psychotic and psychotomimetic states in healthy and schizophrenic subjects. In this study, pictures of natural and artificial objects were presented stereoscopically to 12 healthy male volunteers and depth perception assessed using an operationalized method. The effects of the psychotomimetic S-enantiomer of the anaesthetic ketamine in two different subanaesthetic doses were compared with those of a placebo. In spite of dose dependence and grave subjective and significant objective psychopathology, no significant impairment of binocular depth perception was found with (S)-ketamine. Implications related to memory function, perceptogenesis and ‘bottom-up’ processing in ketamine model psychosis and schizophrenia are discussed.

Passie, T., Karst, M., Borsutzky, M., Wiese, B., Emrich, H. M., & Schneider, U. (2003). Effects of different subanaesthetic doses of (S)-ketamine on psychopathology and binocular depth inversion in man. Journal of Psychopharmacology, 17(1), 51-56. http://dx.doi.org/10.1177/0269881103017001698
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The pharmacology of psilocybin

May 30, 2002 / Mushrooms / Psilocybin, Papers, Publications / By / , , ,

Abstract

Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamin e) is the major psychoactive alkaloid of some species of mushrooms distributed worldwide. These mushrooms represent a growing problem regarding hallucinogenic drug abuse. Despite its experimental medical use in the 1960s, only very few pharmacological data about psilocybin were known until recently. Because of its still growing capacity for abuse and the widely dispersed data this review presents all the available pharmacological data about psilocybin.

Passie, T., Seifert, J., Schneider, U., & Emrich, H. M. (2002). The pharmacology of psilocybin. Addiction Biology, 7(4), 357-364. http://dx.doi.org/10.1080/1355621021000005937

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