Pain
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Inoculation is one of the first and most common experiences of procedural pain in infancy. However, little is known about how needle puncture pain is processed by the central nervous system in children. In this study, we describe for the first time the event-related activity in the infant brain during routine inoculation using electroencephalography. ⋯ Both inoculation event-related potential amplitude and behavioral pain scores increased with age but the 2 measures were not correlated with each other. These components are the first recordings of brain activity in response to real-life needle pain in infants up to a year old. They provide new evidence of postnatal nociceptive processing and, combined with more traditional behavioral pain scores, offer a potentially more sensitive measure for testing the efficacy of analgesic protocols in this age group.
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The contribution of endogenous pain modulation dysfunction to clinical and sensory measures of neuropathic pain (NP) has not been fully explored. Habituation, temporal summation, and heterotopic noxious conditioning stimulus-induced modulation of tonic heat pain intensity were examined in healthy noninjured subjects (n = 10), and above the level of spinal cord injury (SCI) in individuals without (SCI-noNP, n = 10) and with NP (SCI-NP, n = 10). Thermoalgesic thresholds, Cz/AFz contact heat evoked potentials (CHEPs), and phasic or tonic (30 seconds) heat pain intensity were assessed within the C6 dermatome. ⋯ Additionally, the mean conditioned pain modulation response correlated positively with Cz/AFz CHEP amplitude (ρ = 0.8; P = 0.015) and evoked heat pain intensity (ρ = 0.8; P = 0.007) in the SCI-NP group. Stepwise regression analysis revealed that the mean conditioned pain modulation (R = 0.72) correlated with pain severity and pressing spontaneous pain in the SCI-NP group. Comprehensive assessment of sensory dysfunction above the level of injury with tonic thermal test and conditioning stimuli revealed less-efficient endogenous pain modulation in subjects with SCI-NP.
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Central dopamine and norepinephrine regulate behavioral and physiological responses during rewarding and aversive stimuli. Here, we investigated and compared norepinephrine and dopamine transmission in 2 limbic structures, the ventral bed nucleus of the stria terminalis and the nucleus accumbens shell of anesthetized rats, respectively, in response to acute tail pinch, a noxious stimulus. Norepinephrine release in the ventral bed nucleus of the stria terminalis responded monophasically, increasing at the time of the tail pinch and remaining elevated for a period after its cessation. ⋯ At the termination of the stimuli, however, extracellular dopamine either recovered back to or spiked above the initial baseline concentration. These signaling patterns were more clearly observed after administration of selective catecholamine autoreceptor and transporter inhibitors. The results suggest that the opposing responses of these catecholamines can provide integration of noxious inputs to influence behavioral outputs appropriate for survival such as escape or fighting.