Neuroscience
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Bitter reception is mediated by taste receptor cells that coexpress multiple T2Rs, a family of G-protein-coupled receptors. However, it remains elusive how bitter taste information is translated in the brain into appropriate behavioral responses. Here we used a combination of genetic tracing and electrophysiological and immunohistochemical analyses in mice to functionally characterize the neurons in the solitary tract nuclei of the medulla, which receive input from mT2R5-expressing cells. ⋯ The satiety peptide cholecystokinin increases glutamatergic transmission, suggesting an interaction between information processing of taste and the homeostatic control of feeding. Nevertheless, the tracer-labeled neuron types are heterogeneous, and can be classified into catecholamine and pro-opiomelanocortin neurons. Our data reveal that the architectural solution in the first-order central relay that processes information from mT2R5-expressing cells uses unique ensembles of neurons with different neurotransmitters.
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Compression of spinal roots is an important medical problem, which may arise from intervertebral disc herniation, tumor growth or as a result of high energy accidents. Differently from avulsion, root crushing maintains the central/peripheral nervous system (CNS/PNS) connection, although the axons are axotomized and motoneurons degenerate. Such neuronal death may decrease and delay motor function recovery. ⋯ Such treatment also improves the number of synapses immunoreactive against molecules present in inhibitory inputs. Also, an increased number of regenerated axons was obtained in the MSC-treated group, in comparison to the DMEM-treated control. Overall, MSC therapy acutely improved limb strength and gait coordination, indicating a possible clinical application of such treatment following proximal lesions at the CNS/PNS interface.
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Increases in plasma osmolality enhance nitric oxide (NO) levels in magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) and modulate the secretion of both vasopressin (VP) and oxytocin (OT). In this paper, we describe the effects of hypertonicity on the electrical properties of MNCs by focusing on the nitrergic modulation of their activity in this condition. Membrane potentials were measured using the patch clamp technique, in the presence of both glutamatergic and GABAergic neurotransmission blockers, in coronal brain slices of male Wistar rats. ⋯ L-Arginine prevented the increase in fire frequency induced by hypertonic stimulus, and L-NAME (inhibitor of nitric oxide synthase) induced an additional increase in frequency when applied together with the hypertonic solution. Moreover, L-Arginine hyperpolarizes the resting potential and decreases the peak value of the after-hyperpolarization; both effects were blocked by L-NAME and hypertonicity and/or L-NAME reduced the time constant of the rising phase of the after-depolarization. These results demonstrate that an intrinsic nitrergic system is part of the mechanisms controlling the excitability of MNCs of the SON when the internal fluid homeostasis is disturbed.
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While considerable effort has been made to investigate the neural mechanisms of pain, much less effort has been devoted to itch, at least until recently. However, itch is now gaining increasing recognition as a widespread and costly medical and socioeconomic issue. This is accompanied by increasing interest in the underlying neural mechanisms of itch, which has become a vibrant and rapidly-advancing field of research. The goal of the present forefront review is to describe the recent progress that has been made in our understanding of itch mechanisms.
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Learning from feedback involves a network of various cortical and subcortical regions. Although activation in this network has been shown to be especially strong in successful learners, it is currently unclear which of these regions are related to within-subject variation in learning performance. To this aim, 21 subjects performed a probabilistic feedback-learning task consisting of multiple independent Learning blocks and non-learning Control blocks, while functional magnetic resonance imaging data were acquired. ⋯ Finally, activation only in the ventral striatum was associated with within-subject learning performance across the Learning blocks. Taken together, these latter two results are argued to provide the answer to the main research question: ventral striatum activation is associated with within-subject variations in learning performance. The ventral striatum appears to play a vital role in learning by adjusting behavior based on feedback.