The anatomical record : advances in integrative anatomy and evolutionary biology
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The hierarchical relationship of the rat primary somatosensory cortex (S1) and secondary somatosensory cortex (S2) is controversial. The existence of a direct thalamocortical projection from ventral posterolateral thalamic nucleus (VPL) to S2 is a key factor in determining the relative position of S2 in the processing flow. In this study, the inter-connections of forepaw and hindpaw representations in VPL, S1, and S2 were examined by neuroanatomical tracing and electrophysiological approaches. ⋯ In the electrophysiological studies, paired somatic evoked multiunit responses in S1 and S2 were compared. Our results revealed that: (1) VPL forepaw and hindpaw neurons projected to corresponding S1 and S2 areas in a parallel and somatotopic manner; (2) very low percentage of double projecting VPL neurons were found, indicating parallel and independent pathways from forepaw VPL to S1 and S2; (3) forepaw S1 and S2 were symmetrically and reciprocally connected; (4) response latencies of the S1 and S2 multiunits to forepaw stimulation were in accordance with a direct and parallel pathway. This study provides further evidence to support the equivalent hierarchy of S1 and S2 in processing sensory information of the rat.
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Sepsis causes significant alterations in the hepatic macro- and microcirculation. Diverging views exist on global hepatic blood flow during experimental sepsis because of the large variety in animal and sepsis models. Fluid-resuscitated clinical sepsis is characterized by ongoing liver ischemia due to a defective oxygen extraction despite enhanced perfusion. ⋯ Possible interactions between these mediators are not well understood, and their therapeutic manipulation produces equivocal or disappointing results. Whether and how standard resuscitation therapy influences the hepatic microvascular response to sepsis is unknown. Indirect evidence supports the concept that improving the microcirculation may prevent or ameliorate sepsis-induced organ failure.
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Astrocyte activation is involved in the neuropathic pain. As a glutamate scavenger, the glutamate transporter-1 (GLT-1) is exclusively expressed on the astrocytes and probably correlates with astrocyte activation. In the present study, we attempted to clarify the temporal changing courses of astrocyte activation and GLT-1 expression, as well as their correlations induced by a neuropathic pain model, namely, spinal nerve ligation (SNL) in which rapidly appearing (<3 days) and persistent (>21 days) mechanical allodynia and thermal hyperalgesia were presented. ⋯ Our results also demonstrated that SNL induced a marked and long-term (>21 days) activation of astrocytes in the ipsilateral spinal dorsal horn. These results suggest that astrocyte activation, the change of GLT-1 expression and the potential relationship between them might play key roles in the induction and/or maintenance of neuropathic pain. The present results provide novel clues in understanding the mechanisms underlying the involvement of astrocytes and GLT-1 in the neuropathic pain.