Biological Psychology 109 (2015) 111–119 Contents lists available at ScienceDirect Biological Psychology jo ur nal home p age: www.elsevier.com/locate/biopsycho A fluid response: Alpha-amylase reactions to acute laboratory stress are related to sample timing and saliva flow rate Tamás Nagy a,b,∗ , René van Lien c , Gonneke Willemsen c , Gordon Proctor d , Marieke Efting a , Márta Fülöp e , György Bárdos f , Enno C.I. Veerman g , Jos A. Bosch a,h,∗∗ a Department of Clinical Psychology, University of Amsterdam, Weesperplein 4, 1018 XA, Amsterdam, the Netherlands b Doctoral School of Psychology, Education and Psychology, Eötvös Loránd University, Izabella u. 46, 1064, Budapest, Hungary c Department of Biological Psychology, VU University, Van der Boechorststraat 1, 1081 BT, Amsterdam, the Netherlands d Mucosal & Salivary Biology Division, King’s College London Floor 17, Guy’s Tower Guy’s Hospital London SE1 9RT UK e Institute for Cognitive Neuroscience and Psychology, Research Centre of Natural Sciences, Hungarian Academy of Sciences, Magyar Tud´ osok k¨ or´ utja 2, Budapest H-1117, Hungary f Institute of Health Promotion and Sport Sciences, Bogdánffy Ödön u. 10, Budapest, H-1117, Hungary g Department of Oral Biochemistry, Academic Centre of Dentistry (ACTA), Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands h Mannheim Institute of Public Health, Social and Preventive Medicine (MIPH), University of Heidelberg, Ludolf-Krehl-Straße 7-11, D-68167, Mannheim, Germany a r t i c l e i n f o Article history: Received 4 February 2014 Accepted 25 April 2015 Available online 12 May 2015 Keywords: Alpha-amylase Salivary flow rate Acute stress Saliva Sympathetic nervous system Parasympathetic nervous system a b s t r a c t Salivary alpha-amylase (sAA) is used as a sympathetic (SNS) stress marker, though its release is likely co- determined by SNS and parasympathetic (PNS) activation. The SNS and PNS show asynchronous changes during acute stressors, and sAA responses may thus vary with sample timing. Thirty-four participants underwent an eight-minute memory task (MT) and cold pressor task (CPT). Cardiovascular SNS (pre-ejection period, blood pressure) and PNS (heart rate variability) activity were monitored continuously. Unstimulated saliva was collected repeatedly during and after each laboratory stressor, and sAA concentration (U/ml) and secretion (U/minute) determined. Both stressors increased anxiety. The MT caused an immediate and continued cardiac SNS activation, but sAA concentration increased at task cessation only (+54%); i.e., when there was SNS–PNS co-activation. During the MT sAA secretion even decreased (-35%) in conjunction with flow rate and vagal tone. The CPT robustly increased blood pressure but not sAA. In summary, sAA fluctuations did not parallel changes in cardiac SNS activity or anxiety. sAA responses seem contingent on sample timing and flow rate, likely involving both SNS and PNS influences. Verifica- tion using other stressors and contexts seems warranted. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The discovery that the adrenal stress hormone cortisol can be measured reliably and non-invasively in saliva was a method- ological breakthrough in stress research, and much effort has since been dedicated to determine if the assessment of other ∗ Corresponding author at: Doctoral School of Psychology, Education and Psychol- ogy, Eötvös Loránd University, Izabella u. 46, 1064, Budapest, Hungary. Tel.: +36 306276313. ∗∗ Corresponding author at: Department of Clinical Psychology, Faculty of Social and Behavioral Sciences, University of Amsterdam; Weesperplein 4, 1018 XA, Ams- terdam, The Netherlands. Tel.: +31 205256819. E-mail addresses: nagy.tamas@ppk.elte.hu (T. Nagy), J.A.Bosch@uva.nl (J.A. Bosch). neuro-endocrine markers may benefit from the ease of saliva col- lection. As a promising candidate, salivary alpha-amylase (sAA) has gained rapid popularity as a noninvasive marker of sympa- thetic nervous system (SNS) activity (Granger, Kivlighan, El-Sheikh, Gordis, & Stroud, 2007; Nater & Rohleder, 2009; Rohleder & Nater, 2009). sAA is a digestive enzyme that breaks down starch into glucose and maltose, and enzymatic activity (in Units/ml) is used as a proxy for sAA concentration. 1 The use of sAA as a marker of SNS activity seems justified: sAA release from the salivary glands is under strong control of local sympathetic nerves (Proctor & Carpenter, 2007), its salivary concentration rapidly increases 1 sAA concentration is inferred from the amount of enzyme that catalyzes the conversion of 1 mol of substrate (i.e., startch) per minute. http://dx.doi.org/10.1016/j.biopsycho.2015.04.012 0301-0511/© 2015 Elsevier B.V. All rights reserved.