title: Modulation of nociceptive and acoustic startle responses to an unpredictable threat in men and women.
abstract: The present study examined whether a moderately aversive abdominal threat would lead to greater enhancement in affect- and pain-related defensive responding as indexed by the acoustic startle reflex (ASR) and nociceptive flexion reflex (NFR) in women compared to men. We also predicted sex differences in threat-related autonomic arousal measured by skin conductance responses (SCRs) to acoustic startle and noxious sural nerve stimulation. Unpredictable threat was manipulated by alternating 30-second safe ("no abdominal stimulation will be given") and threat ("abdominal stimulation may occur at anytime") periods. The experiment consisted of 2 blocks, each containing 4 safe and 4 threat periods in which the ASR or NFR was randomly probed 9-21 seconds following period onset. Unpredictable abdominal threat potentiated both ASR and NFR responses compared to periods signaling safety. SCRs to acoustic startle probes and noxious sural nerve stimulation were also significantly elevated during the threat vs safe periods. No sex differences in ASR or startle-evoked SCRs emerged. However, nociceptive responding was moderated by sex; females showed significant increases in NFR magnitudes across both safe and threat periods compared to males. Females also showed greater threat-potentiated SCRs to sural nerve stimulation than males. Our findings indicate that both affect- and pain-related defense and arousal systems are strongly influenced by threat of an aversive, unpredictable event, a situation associated with anticipatory anxiety. Females, compared to males, showed greater nociceptive responding and pain modulation when exposed to an unpredictable threatening context, whereas affect-driven ASR responses showed no such sex differentiation.
authors.affiliation: Center for the Neurobiology of Stress, University of California at Los Angeles (UCLA), Los Angeles, CA, USA Department of Medicine-Digestive Diseases, UCLA, Los Angeles, CA, USA VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA Department of Psychiatry and Biobehavioral Sciences, UCLA, Los Angeles, CA, USA Brain Research Institute, UCLA, Los Angeles, CA, USA Department of Psychology, University of Tulsa, Tulsa, OK, USA Department of Physiology, UCLA, Los Angeles, CA, USA.
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Hubbard
authors.forename: Edward
authors.initials: E
authors.lastname: Ornitz
authors.forename: John X
authors.initials: JX
authors.lastname: Gaspar
authors.forename: Suzanne
authors.initials: S
authors.lastname: Smith
authors.forename: Jenny
authors.initials: J
authors.lastname: Amin
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Labus
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Kilpatrick
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Rhudy
authors.forename: Emeran A
authors.initials: EA
authors.lastname: Mayer
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Naliboff
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects / Q000379:methods; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001767:Blinking; D004597:Electroshock / Q000009:adverse effects; D005239:Fear / Q000523:psychology*; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology; D006801:Humans; D008297:Male; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement; D011930:Reaction Time / Q000502:physiology; D013216:Reflex, Startle / Q000502:physiology*; D012727:Sex Characteristics; D013497:Sural Nerve / Q000502:physiology; D055815:Young Adult