Neuroscience
-
The fenestrated microvasculature of the area postrema shows a less restrictive blood-brain barrier than is found in other areas of the CNS. We have studied the expression and relationship of vascular endothelial tight junctional proteins, astrocytes, macrophages, and the extracellular matrix with the extravasation of fluorescently tagged dextrans and sodium fluorescein in the rat area postrema. Glial fibrillary acidic protein (GFAP) -positive astrocytes were present within the area postrema which was surrounded by a dense zone of highly GFAP-reactive astrocytes. ⋯ Three-kilodalton dextran diffused into the parenchyma, but was retained within the boundary of the area postrema at the interface with the highly reactive GFAP-astrocytes, while sodium fluorescein (0.3 kDa) passed from the area postrema into surrounding CNS areas. Our observations suggest that despite the absence of a tight blood-brain barrier, a size selective barrier restricting the movement of blood solutes into the parenchyma is present in the area postrema. We suggest that the rapid uptake by CD163 and CD169 macrophages together with the non-fused laminin immunoreactive layers of the extracellular matrix plays a size selective role in restricting movement of serum proteins and other blood borne macromolecules over 10 kDa in to the area postrema.
-
The intergeniculate leaflet (IGL) is a flat thalamic nucleus that responds to retinal illumination, but also to non-photic input from many brain areas. Its only known function is to modulate the circadian rhythm generated by the suprachiasmatic nucleus. Previously, the firing behavior of cells in IGL has been investigated with extra-cellular recordings, but intracellular recordings from morphologically identified mammalian IGL neurons are lacking. ⋯ This suggests that spontaneous activity was controlled by several, yet undetermined factors in addition to membrane potential. Within the IGL we found a broad range of morphologies without apparent categories and no significant correlation with activity. However, the spontaneous, usually regular, spiking and the rebound depolarization of IGL cells is typical a feature that distinguish them from neurons in ventral and from interneurons in the dorsal lateral geniculate nuclei.
-
This article has been withdrawn consistent with Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). The Publisher apologizes for any inconvenience this may cause.
-
There is experimental evidence indicating that, in humans, avoiding the concurrent activation of non-nociceptive A beta-fibers is a necessary condition for slower A delta-fiber nociceptive input to elicit reproducible event-related brain potentials (ERPs). Similarly, numerous studies have shown that for unmyelinated C-fiber nociceptive input to elicit ERPs, the concurrent activation of A delta-fibers must be avoided. As studies have shown that expectancy of the stimulus greatly conditions the magnitude of these evoked responses, it was hypothesized that the absence of cortical responses related to A delta- or C-fiber somatosensory input that is shortly preceded by A beta- or A delta-fiber somatosensory input could be explained by the fact that the first-arriving afferents render later-arriving afferents highly expected. ⋯ However, their amplitude was significantly reduced. Furthermore, the amplitude of A beta-fiber vertex potentials was similarly reduced by shortly-preceding A delta-fiber input. As expectancy of the stimulus could not account for this reduction, a new hypothesis was proposed, based on processes related to the perceptual fusion of multisensory inputs.
-
Manipulation of glucocorticoid receptor signaling has been shown to alter the acquisition and expression of ethanol-induced locomotor sensitization in mice. It is unknown if other components of the hypothalamic-pituitary-adrenal (HPA)-axis modulate locomotor sensitization resulting from repeated ethanol administration. In the present investigation, we determined if pretreatment with an i.p. injection of CP-154,526, a selective corticotropin releasing factor (CRF) type-1 receptor antagonist, would block the acquisition and/or expression of ethanol-induced locomotor sensitization in male DBA/2J mice. ⋯ These data provide novel evidence that CRF1 receptor signaling modulates the expression of ethanol-induced locomotor sensitization, and add to a growing literature suggesting a role for neurochemicals and hormones associated with the HPA-axis in behavioral sensitization resulting from repeated exposure to drugs of abuse.