Salivary alpha-amylase changes promoted by sustained exposure to affective pictures JUAN P. SÁNCHEZ-NAVARRO, a,b ENRIQUE F. MALDONADO, c JOSÉ M. MARTÍNEZ-SELVA, a,b ALFREDO ENGUIX, d and CARMEN ORTIZ e a Facultad de Psicología, Universidad de Murcia, Murcia, Spain b Instituto Murciano de Investigación Biosanitaria, Murcia, Spain c Facultad de Psicología, Universidad de Málaga, Málaga, Spain d Hospital Universitario “Virgen de la Victoria,” Laboratorio Clínico, Málaga, Spain e Unidad de Gestión Clínica de Análisis Clínicos, Hospital Reina Sofía, Córdoba, Spain. Abstract We studied the changes in salivary alpha-amylase (sAA) and other psychophysiological indices (heart rate, skin conductance, and corrugator supercilii activity) elicited by sustained exposure to affective pictures. Thirty-nine subjects viewed five blocks of pictures depicting mutilations, human attack, neutral scenes, sport/adventure, and erotica. Each block comprised 12 pictures of the same content. Saliva samples were collected before and after each block of pictures. The results showed that mutilation pictures promoted the greatest increase in sAA activity and output, as well as greater corrugator supercilii activity than pleasant pictures. Skin conductance response did not differ among high arousal picture contents. Changes in sAA varied with the affective valence but not with the arousal ratings of the pictures. Our results point to sAA as an index directly related to the unpleasantness elicited by sustained exposure to affective stimuli. Descriptors: Salivary alpha-amylase, Defence response, Heart rate, Skin conductance, Corrugator supercilii, Affective valence Salivary alpha-amylase (sAA) enzyme is produced by the salivary glands and is related to the digestion of macromolecules and the maintenance of oral health (Granger, Kivlighan, El-Sheikh, Gordis, & Stroud, 2007). In recent years, interest in sAA secretion has grown in psychophysiological research because it has been consid- ered as a noninvasive index of autonomic nervous system (ANS) activation (Bosch, Veerman, De Geus, & Proctor, 2011; Ehlert, Erni, Hebisch, & Nater, 2006; Nater & Rohleder, 2009; Rohleder & Nater, 2009). Salivary alpha-amylase activity has been employed as an indi- rect measure of the amount (concentration) of sAA enzyme in saliva and has been related to sympathetic nervous system activity (Bosch et al., 2011; Nater & Rohleder, 2009; Rohleder & Nater, 2009). Parasympathetic activity, however, also influences sAA secretion since (a) some salivary glands are mainly parasympa- thetically innervated, (b) sAA secretion is greater during concomi- tant sympathetic and parasympathetic nerve stimulation in comparison to individual sympathetic or parasympathetic nerve stimulation (Asking, 1985; Asking & Gjorstrup, 1987), and (c) sAA secretion is related to the salivary flow rate, which is mainly determined by parasympathetic activity (Proctor & Carpenter, 2007). Bosch et al. (2011) note that there is often confusion in sAA research due to the absence of a measure of the secretion rate. Salivary alpha-amylase output is associated with the enzymatic activity in relation to the salivary flow rate over a fixed period of time and constitutes, therefore, a better estimate of sympathetic activity associated to sAA secretion (Bosch et al., 2011; Proctor & Carpenter, 2007). Previous research has linked sAA secretion to norepinephrine (NE) levels. In this line, two pharmacological studies have reported that sAA activity increases after the yohimbine test (Ehlert et al., 2006), and decreases after the administration of pro- panolol (van Stegeren, Rohleder, Everaerd, & Wolf, 2006). However, the data associating sAA activity with the peripheral NE levels are weak, in spite of the involvement of this neurotransmit- ter in sAA release (Nater & Rohleder, 2009). Alternatively, some authors have proposed that sAA levels may be an indirect marker of the activity of the sympathetic nervous system and, therefore, related to central NE activity (e.g., Ehlert et al., 2006; Hermans et al., 2011; Segal & Cahill, 2009; van Stegeren et al., 2006; Weymar et al., 2010). A number of studies have found an increase in sAA levels associated with the experience of fear, anxiety, and psychological stress (Nater & Rohleder, 2009; Rohleder & Nater, 2009). For instance, sAA increases have been reported in subjects exposed to laboratory psychosocial stressors, such as the Trier Social Stress This research was supported by a grant from the Seneca Foundation— Murcia Regional Agency for Science and Technology, 08839/PHCS/08. Address correspondence to: Juan P. Sánchez-Navarro, Facultad de Psicología, Universidad de Murcia, 30100 Murcia, Spain. E-mail: jpedro@ um.es Psychophysiology, •• (2012), ••–••. Wiley Periodicals, Inc. Printed in the USA. Copyright © 2012 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2012.01475.x 1