Effects of rapid tryptophan depletion on salivary and plasma cortisol in Alzheimer's disease and the healthy elderly.

Richard J Porter, Elizabeth F Marshall, John T O'Brien

Journal: Journal of psychopharmacology (Oxford, England) 2002;16(1):73-8

PMID: 11949775

Abstract

Serotonergic function is reduced in dementia of Alzheimer type (DAT) and abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis are also common. There is considerable interaction between the two systems. Effects of lowering brain serotonin on salivary and plasma cortisol were assessed in patients with DAT and in control subjects. A double-blind, cross-over design involving administration of two nutritionally balanced amino acid mixtures with or without tryptophan was used. Salivary and plasma cortisol were measured at intervals before and after the drink. DAT patients had higher salivary cortisol than controls. Despite a reduction of approximately 70% in plasma free tryptophan after 4 h in both groups, there was no effect on salivary or plasma cortisol. We conclude that, in subjects with DAT and healthy elderly subjects, acute tryptophan depletion had no effect on cortisol secretion.

Address: Department of Psychological Medicine, Christchurch School of Medicine, University of Otago, New Zealand.

DOI: 10.1177/026988110201600105

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MeSH Terms: Aged, Alzheimer Disease, Area Under Curve, Association Learning, Cross-Over Studies, Double-Blind Method, Female, Humans, Hydrocortisone, Learning, Male, Memory, Short-Term, Neuropsychological Tests, Psychomotor Performance, Saliva, Stress, Psychological, Tryptophan, Verbal Behavior, Verbal Learning