The Journal of neuroscience : the official journal of the Society for Neuroscience
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Comparative Study
Feature-dependent sensitive periods in the development of complex sound representation.
Simple tonal stimuli can shape spectral tuning of cortical neurons during an early epoch of brain development. The effects of complex sound experience on cortical development remain to be determined. ⋯ We found that early exposure to a FM sound resulted in altered characteristic frequency representations and broadened spectral tuning in AI neurons, whereas later exposure to the same sound only led to greater selectivity for the sweep rate and direction of the experienced FM sound. These results indicate that cortical representations of different acoustic features are shaped by complex sounds in a series of distinct sensitive periods.
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Comparative Study
TrkB signaling is required for both the induction and maintenance of tissue and nerve injury-induced persistent pain.
Activation of primary afferent nociceptors produces acute, short-lived pain, and tissue or nerve injury induces long-term enhancement of nociceptive processing, manifested as hypersensitivity to thermal and mechanical stimulation. Here we used a chemical-genetic and pharmacological approach to study the contribution of the receptor tyrosine kinase, type 2 (TrkB) to the generation and maintenance of injury-induced persistent pain. We performed the studies in wild-type mice and transgenic (TrkB(F616A)) mice that express mutant but fully functional TrkB receptors. ⋯ Established hypersensitivity was transiently reversed by intraperitoneal injection of 1NM-PP1. Although interfering with TrkB signaling altered neither acute capsaicin nor formalin-induced pain behavior, the prolonged mechanical hypersensitivity produced by these chemical injuries was prevented by 1NM-PP1 inhibition of TrkB signaling. We conclude that TrkB signaling is not only an important contributor to the induction of heat and mechanical hypersensitivity produced by tissue or nerve injury but also to the persistence of the pain.
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Comparative Study
The ventral premammillary nucleus links fasting-induced changes in leptin levels and coordinated luteinizing hormone secretion.
Physiological conditions of low leptin levels like those observed during negative energy balance are usually characterized by the suppression of luteinizing hormone (LH) secretion and fertility. Leptin administration restores LH levels and reproductive function. Leptin action on LH secretion is thought to be mediated by the brain. ⋯ We further tested the ability of leptin to induce LH secretion in PMV-lesioned fasted animals. We found that complete lesions of the PMV precluded leptin stimulation of LH secretion on fasting. Our findings demonstrate that the PMV is a key site linking changing levels of leptin and coordinated control of reproduction.
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Comparative Study
Long-term plasticity in mouse sensorimotor circuits after rhythmic whisker stimulation.
Mice actively explore their environment by rhythmically sweeping their whiskers. As a consequence, neuronal activity in somatosensory pathways is modulated by the frequency of whisker movement. The potential role of rhythmic neuronal activity for the integration and consolidation of sensory signals, however, remains unexplored. ⋯ We found that it resulted in somatosensory-evoked responses of increased amplitude, highlighting the influence of previous sensory experience in shaping sensory responses. Importantly, environmental enrichment-induced plasticity occluded further potentiation by rhythmic stimulation, indicating that both phenomena share common mechanisms. Overall, our results suggest that natural, rhythmic patterns of whisker activity can modify the cerebral processing of sensory information, providing a possible mechanism for learning during sensory perception.
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Comparative Study
The anatomy of the mesolimbic reward system: a link between personality and the placebo analgesic response.
The anticipation of clinical benefit, a crucial component of placebo analgesia, has been suggested to be a special case of reward anticipation. Since reward processing is closely linked to the ventral striatum and the neurotransmitter dopamine, we examined the relationships between brain gray matter, placebo analgesic response, and personality traits associated with dopaminergic neurotransmission. ⋯ Similarly, GMD in ventral striatum and prefrontal cortex is related to dopamine-related personality traits. Our findings highlight the relationship between placebo and reward and potentially offer ways of identifying subjects who are likely to show large placebo analgesic responses.