Pain
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Both serotonergic and dopaminergic receptor modulation can alter trigeminal nociceptive processing, and descending A11 dopaminergic projections can affect trigeminal nociceptive transmission. Here we aimed to test the interaction between dopamine D(2) and serotonin 5-HT(1B/1D) receptors and their individual and combined effects in order to better understand the relationship of the descending influences of these systems on nociceptive trigeminovascular afferents. Extracellular recordings were made in the rat trigeminocervical complex in response to electrical stimulation of the dura mater and mechanical noxious and innocuous stimulation of the ipsilateral ophthalmic dermatome. ⋯ Both naratriptan alone, and quinpirole combined with GR127935, inhibited firing in the trigeminocervical complex evoked by noxious stimuli, returning it to prelesion baseline, while the response to innocuous stimuli remained facilitated. Immunohistochemical staining demonstrated D(2)-receptor and 5-HT(1B/1D)-receptor colocalization in the trigeminocervical complex. The data suggest that the serotonergic and dopaminergic antinociceptive pathways act simultaneously on neurons in the trigeminocervical complex, and both amine systems need to be functioning for trigeminal sensitization to be reversed.
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Comparative Study
Clinically important difference thresholds of the visual analog scale: a conceptual model for identifying meaningful intraindividual changes for pain intensity.
The aim of this study was to estimate a range of clinically important difference (CID) values of the visual analog scale for pain intensity (VAS-PI), and to assess the effect of patient baseline characteristics on VAS change scores. Data from a prospective cohort study with 678 patients with subacute and chronic temporomandibular disorder pain were analyzed. Patients were divided into 9 cohorts on the basis of the baseline VAS score and the duration of pain. ⋯ For the VAS change scores, the main effect of the variable baseline pain level was significant (F=107.09, P<.001). However, there was no significant baseline pain level by duration of pain interaction effect (F=1.13, P=.340). On the basis of the results, we advocate the choice of a single CID value according to the context of the patient's baseline level of pain.
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The present study examined the prospective value of response expectancies (ie, pain, sleep) and behavioral outcome expectancies (ie, return to function) in the prediction of pain severity and functional limitations 12 months after total knee arthroplasty (TKA). The study sample consisted of 120 individuals (73 women, 47 men) with osteoarthritis of the knee who were scheduled for TKA. Measures of expectancies, pain severity, pain catastrophizing, pain-related fears of movement, and depression were completed prior to surgery. ⋯ Behavioral outcome expectancies partially mediated the relation between catastrophizing and follow-up pain and function. The relation between catastrophizing and follow-up pain severity and functional limitations remained significant even when controlling for behavioral outcome expectancies. The results suggest that interventions designed to specifically target behavioral outcome expectancies and catastrophizing might improve post-surgical outcomes.