Pain
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This study investigated whether one becomes more quickly aware of innocuous somatosensory signals at locations of the body where pain is anticipated. Undergraduate students (N=20) indicated which of 2 stimuli that were administered to each hand using a range of stimulus onset asynchronies (SOAs), was presented first. Participants were instructed that the color of a cue (1 of 2 colors) signaled the possible occurrence of pain on 1 hand (threat trials). ⋯ Results showed that during threat trials tactile stimuli on the hand where pain was expected, were perceived earlier in time than stimuli on the "neutral" hand. These findings demonstrate that the anticipation of pain at a particular location of the body resulted in the prioritization in time of somatosensory sensations at that location, indicating biased attention towards the threatened body part. The value of this study for investigating hypervigilance for somatosensory signals in clinical populations such as patients with chronic lower back pain is discussed.
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Research shows that placebo analgesia can be induced through social observational learning. Our aim was to replicate and extend this result by studying the effect of the sex of both the model and the subject on the magnitude of placebo analgesia induced by social observational learning. Four experimental (1 through 4) and 2 control (5 and 6) groups were observed: groups 1, 3, and 5 were female; groups 2, 4, and 6 were male. ⋯ Regardless of the sex of the subject, nocebo hyperalgesia was greater after the male model was observed. The results show that social observational learning is a mechanism that produces placebo effects. They also indicate that the sex of the model plays an important role in this process.
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Migraine is a highly prevalent, disabling and complex episodic brain disorder whose pathogenesis is poorly understood, due in part to the lack of valid animal models. Here we report behavioral evidence of hallmark migraine features, photophobia and unilateral head pain, in transgenic knock-in mice bearing human familial hemiplegic migraine, type 1 (FHM-1) gain-of-function missense mutations (R192Q or S218L) in the Cacna1a gene encoding the CaV2.1 calcium channel α1 subunit. Photophobia was demonstrated using a modified elevated plus maze in which the safe closed arms were brightly illuminated; mutant mice avoided the light despite showing no differences in the standard (anxiety) version of the test. ⋯ These behaviors were: (1) more frequent in mutant versus wildtype mice; (2) lateralized in mutant but not in wildtype mice; (3) more frequent in females versus males; and (4) dose-dependently normalized by systemic administration of 2 different acute analgesics, rizatriptan and morphine. Furthermore, some of these behaviors were found to be more frequent and severe in 218L compared to 192Q mutants, consistent with the clinical presentation in humans. We suggest that Cacna1a transgenic mice can experience migraine-related head pain and can thus serve as unique tools to study the pathogenesis of migraine and test novel antimigraine agents.