Articles: function.
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Itch is a sensation that promotes the desire to scratch, which can be evoked by mechanical and chemical stimuli. In the spinal cord, neurons expressing the gastrin-releasing peptide receptor (GRPR) have been identified as specific mediators of itch. However, our understanding of the GRPR population in the spinal cord, and thus how these neurons exercise their functions, is limited. ⋯ Additionally, our analysis showed that the Grpr-Cre population expresses Vglut2 mRNA, and mice ablated of Vglut2 in Grpr-Cre cells (Vglut2-lox;Grpr-Cre mice) displayed less spontaneous itch and attenuated responses to both histaminergic and nonhistaminergic agents. We could also show that application of the itch-inducing peptide, natriuretic polypeptide B, induces calcium influx in a subpopulation of Grpr-Cre neurons. To summarize, our data indicate that the Grpr-Cre spinal cord neural population is composed of interneurons that use VGLUT2-mediated signaling for transmitting chemical and spontaneous itch stimuli to the next, currently unknown, neurons in the labeled line of itch.
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Randomized Controlled Trial Multicenter Study
Follow-up at the corrected age of 24 months of preterm newborns receiving continuous infusion of fentanyl for pain control during mechanical ventilation.
The neurodevelopmental impact of fentanyl given to preterm newborns for pain control is still unknown. The aim of this study was to assess the neurodevelopmental impact of 2 regimens of fentanyl administration by a prospective follow-up evaluation. In our previous multicenter, double-blind, randomized controlled trial, 131 mechanically ventilated newborns (gestational age ≤32 weeks) were randomized to fentanyl (continuous infusion of fentanyl + open label boluses of fentanyl) or placebo (continuous infusion of placebo + open label boluses of fentanyl). ⋯ After adjustment for clinical confounders (gestational age, CRIB score, and sex) only eye-hand co-ordination was associated with fentanyl infusion. This study demonstrates that continuous infusion of fentanyl in very preterm infants, given at 1 mcg·kg·h during mechanical ventilation, is associated with a significant decrease in eye and hand co-ordination skills. Longer follow-up is needed to evaluate the impact on future motor, cognitive, and behavioral functions.
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Generalization of fear of movement-related pain across novel but similar movements can lead to fear responses to movements that are actually not associated with pain. The peak-shift effect describes a phenomenon whereby particular novel movements elicit even greater fear responses than the original pain-provoking movement (CS+), because they represent a more extreme version of the CS+. There is great variance in the propensity to generalize as well as the speed of extinction learning when these novel movements are not followed by pain. It can be argued that this variance may be associated with executive function capacity, as individuals may be unable to intentionally inhibit fear responses. This study examined whether executive function capacity contributes to generalization and extinction of generalization as well as peak-shift of conditioned fear of movement-related pain and expectancy. ⋯ Low inhibitory capacity is not associated with slower generalization, but extinction of fear generalization. Fear elicited by a novel safe movement, situated outside the CS+/- continuum on the CS+ side, can be as strong as to the original stimulus predicting the pain-onset.