title: Differentiation of nociceptive- from stress-induced modulatory influences on human reflexes.
abstract: This paper describes a new protocol that addresses the question of whether, in human experiments, modulatory effects of remote nociceptive conditioning stimuli on reflex responses are mediated by the stress induced by the conditioning stimuli. The protocol has been illustrated by a study into the effect of a remote nociceptive conditioning stimulus on an inhibitory jaw reflex. Electromyograms were recorded from an active masseter muscle and inhibitory reflexes were evoked by applying electrical stimuli to the upper lip. This protocol utilised the application of discrete electrical conditioning stimuli applied to the sural nerve prior to the test stimulus. A preliminary experiment determined that the optimal interval between the conditioning and test stimuli, which produced modulatory effects was 100 ms. In the definitive study, computer software was used to deliver control and conditioned sweeps in a double-blind randomised sequence. This resulted in a "stress-equal" protocol in which the level of stress would be the same for both control and conditioned sweeps. Therefore any observed modulatory effects on the reflexes could not have been wholly secondary to stress. This protocol could be adapted to the study of the modulation of other reflexes or evoked sensations by nociceptive conditioning stimuli.
authors.affiliation: Oral Neurophysiology Research Group, Section of Clinical Dental Sciences, The Dental School, University of Dundee, Dundee DD1 4HN, Scotland, UK. a.g.mason@dundee.ac.uk
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Mason
authors.forename: Hilbert W
authors.initials: HW
authors.lastname: van der Glas
authors.forename: Ross M
authors.initials: RM
authors.lastname: Jones
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Cadden
mesh_terms: D003213:Conditioning, Psychological / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D007568:Jaw / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods*; D010865:Pilot Projects; D012018:Reflex / Q000502:physiology*; D012984:Software; D013315:Stress, Psychological; D013497:Sural Nerve / Q000502:physiology