1. Inverse changes in raphe and cortical 5‐HT 1B receptor availability after acute tryptophan depletion in healthy human subjects
- Author
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Sjoerd J. Finnema, Stephen R. Baldassarri, Beata Planeta, Soheila Najafzadeh, Eunkyung Park, Yiyun Huang, Zubin Bhagwagar, Nabeel Nabulsi, Jonas Hannestad, Richard E. Carson, Jim Ropchan, and Kathleen Maloney
- Subjects
0303 health sciences ,medicine.medical_specialty ,Raphe ,Chemistry ,Binding potential ,Grey matter ,Neurotransmission ,Serotonergic ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,medicine.anatomical_structure ,Endocrinology ,Internal medicine ,medicine ,Radioligand ,Serotonin ,030217 neurology & neurosurgery ,5-HT receptor ,030304 developmental biology - Abstract
Serotonergic neurotransmission plays a key role in the pathophysiology and treatment of various neuropsychiatric diseases. The purpose of this study was to investigate changes in serotonergic neurotransmission after acute tryptophan depletion (ATD) using positron emission tomography (PET) with [11 C]P943, a 5-HT1B receptor radioligand previously shown to be sensitive to changes in 5-HT. Five healthy subjects were scanned on a high resolution PET scanner twice on the same day, before and approximately 5 hours after ingesting capsules containing an amino acid mixture that lacks tryptophan. For each scan, emission data were acquired for 120 min after intravenous bolus injection of [11 C]P943. Binding potential (BPND ) values were estimated from parametric images using the second version of the multilinear reference tissue model (MRTM2, t* = 20 min) with cerebellar grey matter used as a reference region. The change in [11 C]P943 binding (ΔBPND , %) was calculated as (BPND,post - BPND,pre )/(BPND,pre ) × 100, and correlation analysis was performed to measure linear associations of ΔBPND between raphe and other regions of interest (ROIs). ΔBPND ranged from -6% to 45% in the raphe, with positive values indicating reduced competition from 5-HT. In cortical regions, ΔBPND ranged from -28% to 7%. While these changes did not reach significance, there were significant negative correlations of ΔBPND of the raphe with those of cerebral cortical regions and the thalamus (e.g., r = -.96, p = .011 for average cortex). These findings support the hypothesis that raphe serotonin is a critical modulator of cortical serotonin release via projecting neurons in healthy human subjects.
- Published
- 2020