Effects of selective and combined serotonin and dopamine depletion on the loudness dependence of the auditory evoked potential (LDAEP) in humans

Authors

  • Barry V. O'Neill,

    Corresponding author
    1. Biological Psychiatry Research Unit, Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
    2. Behavioural Neuroscience Laboratory, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Australia
    • Brain Mapping Unit, Department of Psychiatry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ, UK.
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  • Valérie Guille,

    1. Biological Psychiatry Research Unit, Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
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  • Rodney J. Croft,

    1. Biological Psychiatry Research Unit, Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
    2. Behavioural Neuroscience Laboratory, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Australia
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  • Sumie Leung,

    1. Biological Psychiatry Research Unit, Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
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  • Kirsty E. Scholes,

    1. Centre for Clinical Research in Neuropsychiatry, School of Medicine and Pharmacology, University of Western Australia, Australia
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  • K. Luan Phan,

    1. Brain Imaging and Emotions Lab (BIEL), Department of Psychiatry, The University of Chicago, Chicago, IL, USA
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  • Pradeep J. Nathan

    Corresponding author
    1. Behavioural Neuroscience Laboratory, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Australia
    2. Brain Mapping Unit, Department of Psychiatry, University of Cambridge, Cambridge, UK
    • Brain Mapping Unit, Department of Psychiatry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ, UK.
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Abstract

Background

The loudness dependence of the auditory evoked potential (LDAEP) has been suggested as a possible in vivo measure of central serotonin function. However, more recent studies suggest that the LDAEP may be modulated by multiple neuromodulatory systems in addition to the serotonergic system. Accordingly we further examined the effects of selective serotonin, dopamine and simultaneous serotonin and dopamine depletion on the LDAEP in healthy subjects.

Methods

The study employed a placebo-controlled, double-blind, cross over design. Fourteen subjects were tested under four acute treatment conditions: placebo (balanced amino acid drink), tryptophan (serotonin) depletion (ATD), tyrosine/phenylalanine (dopamine) depletion (ATPD) and combined tryptophan/tyrosine/phenylalanine (serotonin and dopamine) depletion (CMD). Testing was conducted 5.5 h post-depletion and changes in the amplitude of the N1/P2 at varying intensities (60, 70, 80, 90, 100 dB) were examined at CZ.

Results

Greater than 80% plasma precursor depletion was achieved across all conditions. Despite significant depletion of monoamine precursors, ATD, (p = 0.318), ATPD (p = 0.061) and CMD (p = 0.104) had no effects on the LDAEP (60–100 dB).

Conclusion

Acute serotonin and dopamine depletion did not modulate the LDAEP. This finding adds support to growing evidence that the LDAEP is insensitive to acute changes in serotonin and dopamine neurotransmission. Copyright © 2008 John Wiley & Sons, Ltd.

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